• FFmpeg总结(三)AV系列结构体之AVCodecContext


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    这里写图片描写叙述

    描写叙述:主要扩展API的结构体

    New fields can be added to the end with minor version bumps. Removal, reordering and changes to existing fields require a major version bump. You can use AVOptions (av_opt* / av_set/get*()) to access these fields from user applications. The name string for AVOptions options matches the associated command line parameter name and can be found in libavcodec/options_table.h The AVOption/command line parameter names differ in some cases from the C structure field names for historic reasons or brevity. sizeof(AVCodecContext) must not be used outside libav*.

    typedef struct AVCodecContext {
        /**
         * information on struct for av_log
         * - set by avcodec_alloc_context3
         */
        const AVClass *av_class;
        int log_level_offset;
    
        enum AVMediaType codec_type; /* see AVMEDIA_TYPE_xxx */
        const struct AVCodec  *codec;
    #if FF_API_CODEC_NAME
        /**
         * @deprecated this field is not used for anything in libavcodec
         */
        attribute_deprecated
        char             codec_name[32];
    #endif
        enum AVCodecID     codec_id; /* see AV_CODEC_ID_xxx */
    
        /**
         * fourcc (LSB first, so "ABCD" -> ('D'<<24) + ('C'<<16) + ('B'<<8) + 'A').
         * This is used to work around some encoder bugs.
         * A demuxer should set this to what is stored in the field used to identify the codec.
         * If there are multiple such fields in a container then the demuxer should choose the one
         * which maximizes the information about the used codec.
         * If the codec tag field in a container is larger than 32 bits then the demuxer should
         * remap the longer ID to 32 bits with a table or other structure. Alternatively a new
         * extra_codec_tag + size could be added but for this a clear advantage must be demonstrated
         * first.
         * - encoding: Set by user, if not then the default based on codec_id will be used.
         * - decoding: Set by user, will be converted to uppercase by libavcodec during init.
         */
        unsigned int codec_tag;
    
    #if FF_API_STREAM_CODEC_TAG
        /**
         * @deprecated this field is unused
         */
        attribute_deprecated
        unsigned int stream_codec_tag;
    #endif
    
        void *priv_data;
    
        /**
         * Private context used for internal data.
         *
         * Unlike priv_data, this is not codec-specific. It is used in general
         * libavcodec functions.
         */
        struct AVCodecInternal *internal;
    
        /**
         * Private data of the user, can be used to carry app specific stuff.
         * - encoding: Set by user.
         * - decoding: Set by user.
         */
        void *opaque;
    
        /**
         * the average bitrate
         * - encoding: Set by user; unused for constant quantizer encoding.
         * - decoding: Set by user, may be overwritten by libavcodec
         *             if this info is available in the stream
         */
        int64_t bit_rate;
    
        /**
         * number of bits the bitstream is allowed to diverge from the reference.
         *           the reference can be CBR (for CBR pass1) or VBR (for pass2)
         * - encoding: Set by user; unused for constant quantizer encoding.
         * - decoding: unused
         */
        int bit_rate_tolerance;
    
        /**
         * Global quality for codecs which cannot change it per frame.
         * This should be proportional to MPEG-1/2/4 qscale.
         * - encoding: Set by user.
         * - decoding: unused
         */
        int global_quality;
    
        /**
         * - encoding: Set by user.
         * - decoding: unused
         */
        int compression_level;
    #define FF_COMPRESSION_DEFAULT -1
    
        /**
         * AV_CODEC_FLAG_*.
         * - encoding: Set by user.
         * - decoding: Set by user.
         */
        int flags;
    
        /**
         * AV_CODEC_FLAG2_*
         * - encoding: Set by user.
         * - decoding: Set by user.
         */
        int flags2;
    
        /**
         * some codecs need / can use extradata like Huffman tables.
         * MJPEG: Huffman tables
         * rv10: additional flags
         * MPEG-4: global headers (they can be in the bitstream or here)
         * The allocated memory should be AV_INPUT_BUFFER_PADDING_SIZE bytes larger
         * than extradata_size to avoid problems if it is read with the bitstream reader.
         * The bytewise contents of extradata must not depend on the architecture or CPU endianness.
         * - encoding: Set/allocated/freed by libavcodec.
         * - decoding: Set/allocated/freed by user.
         */
        uint8_t *extradata;
        int extradata_size;
    
        /**
         * This is the fundamental unit of time (in seconds) in terms
         * of which frame timestamps are represented. For fixed-fps content,
         * timebase should be 1/framerate and timestamp increments should be
         * identically 1.
         * This often, but not always is the inverse of the frame rate or field rate
         * for video. 1/time_base is not the average frame rate if the frame rate is not
         * constant.
         *
         * Like containers, elementary streams also can store timestamps, 1/time_base
         * is the unit in which these timestamps are specified.
         * As example of such codec time base see ISO/IEC 14496-2:2001(E)
         * vop_time_increment_resolution and fixed_vop_rate
         * (fixed_vop_rate == 0 implies that it is different from the framerate)
         *
         * - encoding: MUST be set by user.
         * - decoding: the use of this field for decoding is deprecated.
         *             Use framerate instead.
         */
        AVRational time_base;
    
        /**
         * For some codecs, the time base is closer to the field rate than the frame rate.
         * Most notably, H.264 and MPEG-2 specify time_base as half of frame duration
         * if no telecine is used ...
         *
         * Set to time_base ticks per frame. Default 1, e.g., H.264/MPEG-2 set it to 2.
         */
        int ticks_per_frame;
    
        /**
         * Codec delay.
         *
         * Encoding: Number of frames delay there will be from the encoder input to
         *           the decoder output. (we assume the decoder matches the spec)
         * Decoding: Number of frames delay in addition to what a standard decoder
         *           as specified in the spec would produce.
         *
         * Video:
         *   Number of frames the decoded output will be delayed relative to the
         *   encoded input.
         *
         * Audio:
         *   For encoding, this field is unused (see initial_padding).
         *
         *   For decoding, this is the number of samples the decoder needs to
         *   output before the decoder's output is valid. When seeking, you should
         *   start decoding this many samples prior to your desired seek point.
         *
         * - encoding: Set by libavcodec.
         * - decoding: Set by libavcodec.
         */
        int delay;
    
    
        /* video only */
        /**
         * picture width / height.
         *
         * @note Those fields may not match the values of the last
         * AVFrame output by avcodec_decode_video2 due frame
         * reordering.
         *
         * - encoding: MUST be set by user.
         * - decoding: May be set by the user before opening the decoder if known e.g.
         *             from the container. Some decoders will require the dimensions
         *             to be set by the caller. During decoding, the decoder may
         *             overwrite those values as required while parsing the data.
         */
        int width, height;
    
        /**
         * Bitstream width / height, may be different from width/height e.g. when
         * the decoded frame is cropped before being output or lowres is enabled.
         *
         * @note Those field may not match the value of the last
         * AVFrame output by avcodec_receive_frame() due frame
         * reordering.
         *
         * - encoding: unused
         * - decoding: May be set by the user before opening the decoder if known
         *             e.g. from the container. During decoding, the decoder may
         *             overwrite those values as required while parsing the data.
         */
        int coded_width, coded_height;
    
    #if FF_API_ASPECT_EXTENDED
    #define FF_ASPECT_EXTENDED 15
    #endif
    
        /**
         * the number of pictures in a group of pictures, or 0 for intra_only
         * - encoding: Set by user.
         * - decoding: unused
         */
        int gop_size;
    
        /**
         * Pixel format, see AV_PIX_FMT_xxx.
         * May be set by the demuxer if known from headers.
         * May be overridden by the decoder if it knows better.
         *
         * @note This field may not match the value of the last
         * AVFrame output by avcodec_receive_frame() due frame
         * reordering.
         *
         * - encoding: Set by user.
         * - decoding: Set by user if known, overridden by libavcodec while
         *             parsing the data.
         */
        enum AVPixelFormat pix_fmt;
    
    #if FF_API_MOTION_EST
        /**
         * This option does nothing
         * @deprecated use codec private options instead
         */
        attribute_deprecated int me_method;
    #endif
    
        /**
         * If non NULL, 'draw_horiz_band' is called by the libavcodec
         * decoder to draw a horizontal band. It improves cache usage. Not
         * all codecs can do that. You must check the codec capabilities
         * beforehand.
         * When multithreading is used, it may be called from multiple threads
         * at the same time; threads might draw different parts of the same AVFrame,
         * or multiple AVFrames, and there is no guarantee that slices will be drawn
         * in order.
         * The function is also used by hardware acceleration APIs.
         * It is called at least once during frame decoding to pass
         * the data needed for hardware render.
         * In that mode instead of pixel data, AVFrame points to
         * a structure specific to the acceleration API. The application
         * reads the structure and can change some fields to indicate progress
         * or mark state.
         * - encoding: unused
         * - decoding: Set by user.
         * @param height the height of the slice
         * @param y the y position of the slice
         * @param type 1->top field, 2->bottom field, 3->frame
         * @param offset offset into the AVFrame.data from which the slice should be read
         */
        void (*draw_horiz_band)(struct AVCodecContext *s,
                                const AVFrame *src, int offset[AV_NUM_DATA_POINTERS],
                                int y, int type, int height);
    
        /**
         * callback to negotiate the pixelFormat
         * @param fmt is the list of formats which are supported by the codec,
         * it is terminated by -1 as 0 is a valid format, the formats are ordered by quality.
         * The first is always the native one.
         * @note The callback may be called again immediately if initialization for
         * the selected (hardware-accelerated) pixel format failed.
         * @warning Behavior is undefined if the callback returns a value not
         * in the fmt list of formats.
         * @return the chosen format
         * - encoding: unused
         * - decoding: Set by user, if not set the native format will be chosen.
         */
        enum AVPixelFormat (*get_format)(struct AVCodecContext *s, const enum AVPixelFormat * fmt);
    
        /**
         * maximum number of B-frames between non-B-frames
         * Note: The output will be delayed by max_b_frames+1 relative to the input.
         * - encoding: Set by user.
         * - decoding: unused
         */
        int max_b_frames;
    
        /**
         * qscale factor between IP and B-frames
         * If > 0 then the last P-frame quantizer will be used (q= lastp_q*factor+offset).
         * If < 0 then normal ratecontrol will be done (q= -normal_q*factor+offset).
         * - encoding: Set by user.
         * - decoding: unused
         */
        float b_quant_factor;
    
    #if FF_API_RC_STRATEGY
        /** @deprecated use codec private option instead */
        attribute_deprecated int rc_strategy;
    #define FF_RC_STRATEGY_XVID 1
    #endif
    
    #if FF_API_PRIVATE_OPT
        /** @deprecated use encoder private options instead */
        attribute_deprecated
        int b_frame_strategy;
    #endif
    
        /**
         * qscale offset between IP and B-frames
         * - encoding: Set by user.
         * - decoding: unused
         */
        float b_quant_offset;
    
        /**
         * Size of the frame reordering buffer in the decoder.
         * For MPEG-2 it is 1 IPB or 0 low delay IP.
         * - encoding: Set by libavcodec.
         * - decoding: Set by libavcodec.
         */
        int has_b_frames;
    
    #if FF_API_PRIVATE_OPT
        /** @deprecated use encoder private options instead */
        attribute_deprecated
        int mpeg_quant;
    #endif
    
        /**
         * qscale factor between P- and I-frames
         * If > 0 then the last P-frame quantizer will be used (q = lastp_q * factor + offset).
         * If < 0 then normal ratecontrol will be done (q= -normal_q*factor+offset).
         * - encoding: Set by user.
         * - decoding: unused
         */
        float i_quant_factor;
    
        /**
         * qscale offset between P and I-frames
         * - encoding: Set by user.
         * - decoding: unused
         */
        float i_quant_offset;
    
        /**
         * luminance masking (0-> disabled)
         * - encoding: Set by user.
         * - decoding: unused
         */
        float lumi_masking;
    
        /**
         * temporary complexity masking (0-> disabled)
         * - encoding: Set by user.
         * - decoding: unused
         */
        float temporal_cplx_masking;
    
        /**
         * spatial complexity masking (0-> disabled)
         * - encoding: Set by user.
         * - decoding: unused
         */
        float spatial_cplx_masking;
    
        /**
         * p block masking (0-> disabled)
         * - encoding: Set by user.
         * - decoding: unused
         */
        float p_masking;
    
        /**
         * darkness masking (0-> disabled)
         * - encoding: Set by user.
         * - decoding: unused
         */
        float dark_masking;
    
        /**
         * slice count
         * - encoding: Set by libavcodec.
         * - decoding: Set by user (or 0).
         */
        int slice_count;
    
    #if FF_API_PRIVATE_OPT
        /** @deprecated use encoder private options instead */
        attribute_deprecated
         int prediction_method;
    #define FF_PRED_LEFT   0
    #define FF_PRED_PLANE  1
    #define FF_PRED_MEDIAN 2
    #endif
    
        /**
         * slice offsets in the frame in bytes
         * - encoding: Set/allocated by libavcodec.
         * - decoding: Set/allocated by user (or NULL).
         */
        int *slice_offset;
    
        /**
         * sample aspect ratio (0 if unknown)
         * That is the width of a pixel divided by the height of the pixel.
         * Numerator and denominator must be relatively prime and smaller than 256 for some video standards.
         * - encoding: Set by user.
         * - decoding: Set by libavcodec.
         */
        AVRational sample_aspect_ratio;
    
        /**
         * motion estimation comparison function
         * - encoding: Set by user.
         * - decoding: unused
         */
        int me_cmp;
        /**
         * subpixel motion estimation comparison function
         * - encoding: Set by user.
         * - decoding: unused
         */
        int me_sub_cmp;
        /**
         * macroblock comparison function (not supported yet)
         * - encoding: Set by user.
         * - decoding: unused
         */
        int mb_cmp;
        /**
         * interlaced DCT comparison function
         * - encoding: Set by user.
         * - decoding: unused
         */
        int ildct_cmp;
    #define FF_CMP_SAD    0
    #define FF_CMP_SSE    1
    #define FF_CMP_SATD   2
    #define FF_CMP_DCT    3
    #define FF_CMP_PSNR   4
    #define FF_CMP_BIT    5
    #define FF_CMP_RD     6
    #define FF_CMP_ZERO   7
    #define FF_CMP_VSAD   8
    #define FF_CMP_VSSE   9
    #define FF_CMP_NSSE   10
    #define FF_CMP_W53    11
    #define FF_CMP_W97    12
    #define FF_CMP_DCTMAX 13
    #define FF_CMP_DCT264 14
    #define FF_CMP_CHROMA 256
    
        /**
         * ME diamond size & shape
         * - encoding: Set by user.
         * - decoding: unused
         */
        int dia_size;
    
        /**
         * amount of previous MV predictors (2a+1 x 2a+1 square)
         * - encoding: Set by user.
         * - decoding: unused
         */
        int last_predictor_count;
    
    #if FF_API_PRIVATE_OPT
        /** @deprecated use encoder private options instead */
        attribute_deprecated
        int pre_me;
    #endif
    
        /**
         * motion estimation prepass comparison function
         * - encoding: Set by user.
         * - decoding: unused
         */
        int me_pre_cmp;
    
        /**
         * ME prepass diamond size & shape
         * - encoding: Set by user.
         * - decoding: unused
         */
        int pre_dia_size;
    
        /**
         * subpel ME quality
         * - encoding: Set by user.
         * - decoding: unused
         */
        int me_subpel_quality;
    
    #if FF_API_AFD
        /**
         * DTG active format information (additional aspect ratio
         * information only used in DVB MPEG-2 transport streams)
         * 0 if not set.
         *
         * - encoding: unused
         * - decoding: Set by decoder.
         * @deprecated Deprecated in favor of AVSideData
         */
        attribute_deprecated int dtg_active_format;
    #define FF_DTG_AFD_SAME         8
    #define FF_DTG_AFD_4_3          9
    #define FF_DTG_AFD_16_9         10
    #define FF_DTG_AFD_14_9         11
    #define FF_DTG_AFD_4_3_SP_14_9  13
    #define FF_DTG_AFD_16_9_SP_14_9 14
    #define FF_DTG_AFD_SP_4_3       15
    #endif /* FF_API_AFD */
    
        /**
         * maximum motion estimation search range in subpel units
         * If 0 then no limit.
         *
         * - encoding: Set by user.
         * - decoding: unused
         */
        int me_range;
    
    #if FF_API_QUANT_BIAS
        /**
         * @deprecated use encoder private option instead
         */
        attribute_deprecated int intra_quant_bias;
    #define FF_DEFAULT_QUANT_BIAS 999999
    
        /**
         * @deprecated use encoder private option instead
         */
        attribute_deprecated int inter_quant_bias;
    #endif
    
        /**
         * slice flags
         * - encoding: unused
         * - decoding: Set by user.
         */
        int slice_flags;
    #define SLICE_FLAG_CODED_ORDER    0x0001 ///< draw_horiz_band() is called in coded order instead of display
    #define SLICE_FLAG_ALLOW_FIELD    0x0002 ///< allow draw_horiz_band() with field slices (MPEG-2 field pics)
    #define SLICE_FLAG_ALLOW_PLANE    0x0004 ///< allow draw_horiz_band() with 1 component at a time (SVQ1)
    
    #if FF_API_XVMC
        /**
         * XVideo Motion Acceleration
         * - encoding: forbidden
         * - decoding: set by decoder
         * @deprecated XvMC doesn't need it anymore.
         */
        attribute_deprecated int xvmc_acceleration;
    #endif /* FF_API_XVMC */
    
        /**
         * macroblock decision mode
         * - encoding: Set by user.
         * - decoding: unused
         */
        int mb_decision;
    #define FF_MB_DECISION_SIMPLE 0        ///< uses mb_cmp
    #define FF_MB_DECISION_BITS   1        ///< chooses the one which needs the fewest bits
    #define FF_MB_DECISION_RD     2        ///< rate distortion
    
        /**
         * custom intra quantization matrix
         * - encoding: Set by user, can be NULL.
         * - decoding: Set by libavcodec.
         */
        uint16_t *intra_matrix;
    
        /**
         * custom inter quantization matrix
         * - encoding: Set by user, can be NULL.
         * - decoding: Set by libavcodec.
         */
        uint16_t *inter_matrix;
    
    #if FF_API_PRIVATE_OPT
        /** @deprecated use encoder private options instead */
        attribute_deprecated
        int scenechange_threshold;
    
        /** @deprecated use encoder private options instead */
        attribute_deprecated
        int noise_reduction;
    #endif
    
    #if FF_API_MPV_OPT
        /**
         * @deprecated this field is unused
         */
        attribute_deprecated
        int me_threshold;
    
        /**
         * @deprecated this field is unused
         */
        attribute_deprecated
        int mb_threshold;
    #endif
    
        /**
         * precision of the intra DC coefficient - 8
         * - encoding: Set by user.
         * - decoding: Set by libavcodec
         */
        int intra_dc_precision;
    
        /**
         * Number of macroblock rows at the top which are skipped.
         * - encoding: unused
         * - decoding: Set by user.
         */
        int skip_top;
    
        /**
         * Number of macroblock rows at the bottom which are skipped.
         * - encoding: unused
         * - decoding: Set by user.
         */
        int skip_bottom;
    
    #if FF_API_MPV_OPT
        /**
         * @deprecated use encoder private options instead
         */
        attribute_deprecated
        float border_masking;
    #endif
    
        /**
         * minimum MB Lagrange multiplier
         * - encoding: Set by user.
         * - decoding: unused
         */
        int mb_lmin;
    
        /**
         * maximum MB Lagrange multiplier
         * - encoding: Set by user.
         * - decoding: unused
         */
        int mb_lmax;
    
    #if FF_API_PRIVATE_OPT
        /**
         * @deprecated use encoder private options instead
         */
        attribute_deprecated
        int me_penalty_compensation;
    #endif
    
        /**
         * - encoding: Set by user.
         * - decoding: unused
         */
        int bidir_refine;
    
    #if FF_API_PRIVATE_OPT
        /** @deprecated use encoder private options instead */
        attribute_deprecated
        int brd_scale;
    #endif
    
        /**
         * minimum GOP size
         * - encoding: Set by user.
         * - decoding: unused
         */
        int keyint_min;
    
        /**
         * number of reference frames
         * - encoding: Set by user.
         * - decoding: Set by lavc.
         */
        int refs;
    
    #if FF_API_PRIVATE_OPT
        /** @deprecated use encoder private options instead */
        attribute_deprecated
        int chromaoffset;
    #endif
    
    #if FF_API_UNUSED_MEMBERS
        /**
         * Multiplied by qscale for each frame and added to scene_change_score.
         * - encoding: Set by user.
         * - decoding: unused
         */
        attribute_deprecated int scenechange_factor;
    #endif
    
        /**
         * Note: Value depends upon the compare function used for fullpel ME.
         * - encoding: Set by user.
         * - decoding: unused
         */
        int mv0_threshold;
    
    #if FF_API_PRIVATE_OPT
        /** @deprecated use encoder private options instead */
        attribute_deprecated
        int b_sensitivity;
    #endif
    
        /**
         * Chromaticity coordinates of the source primaries.
         * - encoding: Set by user
         * - decoding: Set by libavcodec
         */
        enum AVColorPrimaries color_primaries;
    
        /**
         * Color Transfer Characteristic.
         * - encoding: Set by user
         * - decoding: Set by libavcodec
         */
        enum AVColorTransferCharacteristic color_trc;
    
        /**
         * YUV colorspace type.
         * - encoding: Set by user
         * - decoding: Set by libavcodec
         */
        enum AVColorSpace colorspace;
    
        /**
         * MPEG vs JPEG YUV range.
         * - encoding: Set by user
         * - decoding: Set by libavcodec
         */
        enum AVColorRange color_range;
    
        /**
         * This defines the location of chroma samples.
         * - encoding: Set by user
         * - decoding: Set by libavcodec
         */
        enum AVChromaLocation chroma_sample_location;
    
        /**
         * Number of slices.
         * Indicates number of picture subdivisions. Used for parallelized
         * decoding.
         * - encoding: Set by user
         * - decoding: unused
         */
        int slices;
    
        /** Field order
         * - encoding: set by libavcodec
         * - decoding: Set by user.
         */
        enum AVFieldOrder field_order;
    
        /* audio only */
        int sample_rate; ///< samples per second
        int channels;    ///< number of audio channels
    
        /**
         * audio sample format
         * - encoding: Set by user.
         * - decoding: Set by libavcodec.
         */
        enum AVSampleFormat sample_fmt;  ///< sample format
    
        /* The following data should not be initialized. */
        /**
         * Number of samples per channel in an audio frame.
         *
         * - encoding: set by libavcodec in avcodec_open2(). Each submitted frame
         *   except the last must contain exactly frame_size samples per channel.
         *   May be 0 when the codec has AV_CODEC_CAP_VARIABLE_FRAME_SIZE set, then the
         *   frame size is not restricted.
         * - decoding: may be set by some decoders to indicate constant frame size
         */
        int frame_size;
    
        /**
         * Frame counter, set by libavcodec.
         *
         * - decoding: total number of frames returned from the decoder so far.
         * - encoding: total number of frames passed to the encoder so far.
         *
         *   @note the counter is not incremented if encoding/decoding resulted in
         *   an error.
         */
        int frame_number;
    
        /**
         * number of bytes per packet if constant and known or 0
         * Used by some WAV based audio codecs.
         */
        int block_align;
    
        /**
         * Audio cutoff bandwidth (0 means "automatic")
         * - encoding: Set by user.
         * - decoding: unused
         */
        int cutoff;
    
        /**
         * Audio channel layout.
         * - encoding: set by user.
         * - decoding: set by user, may be overwritten by libavcodec.
         */
        uint64_t channel_layout;
    
        /**
         * Request decoder to use this channel layout if it can (0 for default)
         * - encoding: unused
         * - decoding: Set by user.
         */
        uint64_t request_channel_layout;
    
        /**
         * Type of service that the audio stream conveys.
         * - encoding: Set by user.
         * - decoding: Set by libavcodec.
         */
        enum AVAudioServiceType audio_service_type;
    
        /**
         * desired sample format
         * - encoding: Not used.
         * - decoding: Set by user.
         * Decoder will decode to this format if it can.
         */
        enum AVSampleFormat request_sample_fmt;
    
        /**
         * This callback is called at the beginning of each frame to get data
         * buffer(s) for it. There may be one contiguous buffer for all the data or
         * there may be a buffer per each data plane or anything in between. What
         * this means is, you may set however many entries in buf[] you feel necessary.
         * Each buffer must be reference-counted using the AVBuffer API (see description
         * of buf[] below).
         *
         * The following fields will be set in the frame before this callback is
         * called:
         * - format
         * - width, height (video only)
         * - sample_rate, channel_layout, nb_samples (audio only)
         * Their values may differ from the corresponding values in
         * AVCodecContext. This callback must use the frame values, not the codec
         * context values, to calculate the required buffer size.
         *
         * This callback must fill the following fields in the frame:
         * - data[]
         * - linesize[]
         * - extended_data:
         *   * if the data is planar audio with more than 8 channels, then this
         *     callback must allocate and fill extended_data to contain all pointers
         *     to all data planes. data[] must hold as many pointers as it can.
         *     extended_data must be allocated with av_malloc() and will be freed in
         *     av_frame_unref().
         *   * otherwise extended_data must point to data
         * - buf[] must contain one or more pointers to AVBufferRef structures. Each of
         *   the frame's data and extended_data pointers must be contained in these. That
         *   is, one AVBufferRef for each allocated chunk of memory, not necessarily one
         *   AVBufferRef per data[] entry. See: av_buffer_create(), av_buffer_alloc(),
         *   and av_buffer_ref().
         * - extended_buf and nb_extended_buf must be allocated with av_malloc() by
         *   this callback and filled with the extra buffers if there are more
         *   buffers than buf[] can hold. extended_buf will be freed in
         *   av_frame_unref().
         *
         * If AV_CODEC_CAP_DR1 is not set then get_buffer2() must call
         * avcodec_default_get_buffer2() instead of providing buffers allocated by
         * some other means.
         *
         * Each data plane must be aligned to the maximum required by the target
         * CPU.
         *
         * @see avcodec_default_get_buffer2()
         *
         * Video:
         *
         * If AV_GET_BUFFER_FLAG_REF is set in flags then the frame may be reused
         * (read and/or written to if it is writable) later by libavcodec.
         *
         * avcodec_align_dimensions2() should be used to find the required width and
         * height, as they normally need to be rounded up to the next multiple of 16.
         *
         * Some decoders do not support linesizes changing between frames.
         *
         * If frame multithreading is used and thread_safe_callbacks is set,
         * this callback may be called from a different thread, but not from more
         * than one at once. Does not need to be reentrant.
         *
         * @see avcodec_align_dimensions2()
         *
         * Audio:
         *
         * Decoders request a buffer of a particular size by setting
         * AVFrame.nb_samples prior to calling get_buffer2(). The decoder may,
         * however, utilize only part of the buffer by setting AVFrame.nb_samples
         * to a smaller value in the output frame.
         *
         * As a convenience, av_samples_get_buffer_size() and
         * av_samples_fill_arrays() in libavutil may be used by custom get_buffer2()
         * functions to find the required data size and to fill data pointers and
         * linesize. In AVFrame.linesize, only linesize[0] may be set for audio
         * since all planes must be the same size.
         *
         * @see av_samples_get_buffer_size(), av_samples_fill_arrays()
         *
         * - encoding: unused
         * - decoding: Set by libavcodec, user can override.
         */
        int (*get_buffer2)(struct AVCodecContext *s, AVFrame *frame, int flags);
    
        /**
         * If non-zero, the decoded audio and video frames returned from
         * avcodec_decode_video2() and avcodec_decode_audio4() are reference-counted
         * and are valid indefinitely. The caller must free them with
         * av_frame_unref() when they are not needed anymore.
         * Otherwise, the decoded frames must not be freed by the caller and are
         * only valid until the next decode call.
         *
         * This is always automatically enabled if avcodec_receive_frame() is used.
         *
         * - encoding: unused
         * - decoding: set by the caller before avcodec_open2().
         */
        int refcounted_frames;
    
        /* - encoding parameters */
        float qcompress;  ///< amount of qscale change between easy & hard scenes (0.0-1.0)
        float qblur;      ///< amount of qscale smoothing over time (0.0-1.0)
    
        /**
         * minimum quantizer
         * - encoding: Set by user.
         * - decoding: unused
         */
        int qmin;
    
        /**
         * maximum quantizer
         * - encoding: Set by user.
         * - decoding: unused
         */
        int qmax;
    
        /**
         * maximum quantizer difference between frames
         * - encoding: Set by user.
         * - decoding: unused
         */
        int max_qdiff;
    
    #if FF_API_MPV_OPT
        /**
         * @deprecated use encoder private options instead
         */
        attribute_deprecated
        float rc_qsquish;
    
        attribute_deprecated
        float rc_qmod_amp;
        attribute_deprecated
        int rc_qmod_freq;
    #endif
    
        /**
         * decoder bitstream buffer size
         * - encoding: Set by user.
         * - decoding: unused
         */
        int rc_buffer_size;
    
        /**
         * ratecontrol override, see RcOverride
         * - encoding: Allocated/set/freed by user.
         * - decoding: unused
         */
        int rc_override_count;
        RcOverride *rc_override;
    
    #if FF_API_MPV_OPT
        /**
         * @deprecated use encoder private options instead
         */
        attribute_deprecated
        const char *rc_eq;
    #endif
    
        /**
         * maximum bitrate
         * - encoding: Set by user.
         * - decoding: Set by user, may be overwritten by libavcodec.
         */
        int64_t rc_max_rate;
    
        /**
         * minimum bitrate
         * - encoding: Set by user.
         * - decoding: unused
         */
        int64_t rc_min_rate;
    
    #if FF_API_MPV_OPT
        /**
         * @deprecated use encoder private options instead
         */
        attribute_deprecated
        float rc_buffer_aggressivity;
    
        attribute_deprecated
        float rc_initial_cplx;
    #endif
    
        /**
         * Ratecontrol attempt to use, at maximum, <value> of what can be used without an underflow.
         * - encoding: Set by user.
         * - decoding: unused.
         */
        float rc_max_available_vbv_use;
    
        /**
         * Ratecontrol attempt to use, at least, <value> times the amount needed to prevent a vbv overflow.
         * - encoding: Set by user.
         * - decoding: unused.
         */
        float rc_min_vbv_overflow_use;
    
        /**
         * Number of bits which should be loaded into the rc buffer before decoding starts.
         * - encoding: Set by user.
         * - decoding: unused
         */
        int rc_initial_buffer_occupancy;
    
    #if FF_API_CODER_TYPE
    #define FF_CODER_TYPE_VLC       0
    #define FF_CODER_TYPE_AC        1
    #define FF_CODER_TYPE_RAW       2
    #define FF_CODER_TYPE_RLE       3
    #if FF_API_UNUSED_MEMBERS
    #define FF_CODER_TYPE_DEFLATE   4
    #endif /* FF_API_UNUSED_MEMBERS */
        /**
         * @deprecated use encoder private options instead
         */
        attribute_deprecated
        int coder_type;
    #endif /* FF_API_CODER_TYPE */
    
    #if FF_API_PRIVATE_OPT
        /** @deprecated use encoder private options instead */
        attribute_deprecated
        int context_model;
    #endif
    
    #if FF_API_MPV_OPT
        /**
         * @deprecated use encoder private options instead
         */
        attribute_deprecated
        int lmin;
    
        /**
         * @deprecated use encoder private options instead
         */
        attribute_deprecated
        int lmax;
    #endif
    
    #if FF_API_PRIVATE_OPT
        /** @deprecated use encoder private options instead */
        attribute_deprecated
        int frame_skip_threshold;
    
        /** @deprecated use encoder private options instead */
        attribute_deprecated
        int frame_skip_factor;
    
        /** @deprecated use encoder private options instead */
        attribute_deprecated
        int frame_skip_exp;
    
        /** @deprecated use encoder private options instead */
        attribute_deprecated
        int frame_skip_cmp;
    #endif /* FF_API_PRIVATE_OPT */
    
        /**
         * trellis RD quantization
         * - encoding: Set by user.
         * - decoding: unused
         */
        int trellis;
    
    #if FF_API_PRIVATE_OPT
        /** @deprecated use encoder private options instead */
        attribute_deprecated
        int min_prediction_order;
    
        /** @deprecated use encoder private options instead */
        attribute_deprecated
        int max_prediction_order;
    
        /** @deprecated use encoder private options instead */
        attribute_deprecated
        int64_t timecode_frame_start;
    #endif
    
    #if FF_API_RTP_CALLBACK
        /**
         * @deprecated unused
         */
        /* The RTP callback: This function is called    */
        /* every time the encoder has a packet to send. */
        /* It depends on the encoder if the data starts */
        /* with a Start Code (it should). H.263 does.   */
        /* mb_nb contains the number of macroblocks     */
        /* encoded in the RTP payload.                  */
        attribute_deprecated
        void (*rtp_callback)(struct AVCodecContext *avctx, void *data, int size, int mb_nb);
    #endif
    
    #if FF_API_PRIVATE_OPT
        /** @deprecated use encoder private options instead */
        attribute_deprecated
        int rtp_payload_size;   /* The size of the RTP payload: the coder will  */
                                /* do its best to deliver a chunk with size     */
                                /* below rtp_payload_size, the chunk will start */
                                /* with a start code on some codecs like H.263. */
                                /* This doesn't take account of any particular  */
                                /* headers inside the transmitted RTP payload.  */
    #endif
    
    #if FF_API_STAT_BITS
        /* statistics, used for 2-pass encoding */
        attribute_deprecated
        int mv_bits;
        attribute_deprecated
        int header_bits;
        attribute_deprecated
        int i_tex_bits;
        attribute_deprecated
        int p_tex_bits;
        attribute_deprecated
        int i_count;
        attribute_deprecated
        int p_count;
        attribute_deprecated
        int skip_count;
        attribute_deprecated
        int misc_bits;
    
        /** @deprecated this field is unused */
        attribute_deprecated
        int frame_bits;
    #endif
    
        /**
         * pass1 encoding statistics output buffer
         * - encoding: Set by libavcodec.
         * - decoding: unused
         */
        char *stats_out;
    
        /**
         * pass2 encoding statistics input buffer
         * Concatenated stuff from stats_out of pass1 should be placed here.
         * - encoding: Allocated/set/freed by user.
         * - decoding: unused
         */
        char *stats_in;
    
        /**
         * Work around bugs in encoders which sometimes cannot be detected automatically.
         * - encoding: Set by user
         * - decoding: Set by user
         */
        int workaround_bugs;
    #define FF_BUG_AUTODETECT       1  ///< autodetection
    #if FF_API_OLD_MSMPEG4
    #define FF_BUG_OLD_MSMPEG4      2
    #endif
    #define FF_BUG_XVID_ILACE       4
    #define FF_BUG_UMP4             8
    #define FF_BUG_NO_PADDING       16
    #define FF_BUG_AMV              32
    #if FF_API_AC_VLC
    #define FF_BUG_AC_VLC           0  ///< Will be removed, libavcodec can now handle these non-compliant files by default.
    #endif
    #define FF_BUG_QPEL_CHROMA      64
    #define FF_BUG_STD_QPEL         128
    #define FF_BUG_QPEL_CHROMA2     256
    #define FF_BUG_DIRECT_BLOCKSIZE 512
    #define FF_BUG_EDGE             1024
    #define FF_BUG_HPEL_CHROMA      2048
    #define FF_BUG_DC_CLIP          4096
    #define FF_BUG_MS               8192 ///< Work around various bugs in Microsoft's broken decoders.
    #define FF_BUG_TRUNCATED       16384
    
        /**
         * strictly follow the standard (MPEG-4, ...).
         * - encoding: Set by user.
         * - decoding: Set by user.
         * Setting this to STRICT or higher means the encoder and decoder will
         * generally do stupid things, whereas setting it to unofficial or lower
         * will mean the encoder might produce output that is not supported by all
         * spec-compliant decoders. Decoders don't differentiate between normal,
         * unofficial and experimental (that is, they always try to decode things
         * when they can) unless they are explicitly asked to behave stupidly
         * (=strictly conform to the specs)
         */
        int strict_std_compliance;
    #define FF_COMPLIANCE_VERY_STRICT   2 ///< Strictly conform to an older more strict version of the spec or reference software.
    #define FF_COMPLIANCE_STRICT        1 ///< Strictly conform to all the things in the spec no matter what consequences.
    #define FF_COMPLIANCE_NORMAL        0
    #define FF_COMPLIANCE_UNOFFICIAL   -1 ///< Allow unofficial extensions
    #define FF_COMPLIANCE_EXPERIMENTAL -2 ///< Allow nonstandardized experimental things.
    
        /**
         * error concealment flags
         * - encoding: unused
         * - decoding: Set by user.
         */
        int error_concealment;
    #define FF_EC_GUESS_MVS   1
    #define FF_EC_DEBLOCK     2
    #define FF_EC_FAVOR_INTER 256
    
        /**
         * debug
         * - encoding: Set by user.
         * - decoding: Set by user.
         */
        int debug;
    #define FF_DEBUG_PICT_INFO   1
    #define FF_DEBUG_RC          2
    #define FF_DEBUG_BITSTREAM   4
    #define FF_DEBUG_MB_TYPE     8
    #define FF_DEBUG_QP          16
    #if FF_API_DEBUG_MV
    /**
     * @deprecated this option does nothing
     */
    #define FF_DEBUG_MV          32
    #endif
    #define FF_DEBUG_DCT_COEFF   0x00000040
    #define FF_DEBUG_SKIP        0x00000080
    #define FF_DEBUG_STARTCODE   0x00000100
    #if FF_API_UNUSED_MEMBERS
    #define FF_DEBUG_PTS         0x00000200
    #endif /* FF_API_UNUSED_MEMBERS */
    #define FF_DEBUG_ER          0x00000400
    #define FF_DEBUG_MMCO        0x00000800
    #define FF_DEBUG_BUGS        0x00001000
    #if FF_API_DEBUG_MV
    #define FF_DEBUG_VIS_QP      0x00002000 ///< only access through AVOptions from outside libavcodec
    #define FF_DEBUG_VIS_MB_TYPE 0x00004000 ///< only access through AVOptions from outside libavcodec
    #endif
    #define FF_DEBUG_BUFFERS     0x00008000
    #define FF_DEBUG_THREADS     0x00010000
    #define FF_DEBUG_GREEN_MD    0x00800000
    #define FF_DEBUG_NOMC        0x01000000
    
    #if FF_API_DEBUG_MV
        /**
         * debug
         * Code outside libavcodec should access this field using AVOptions
         * - encoding: Set by user.
         * - decoding: Set by user.
         */
        int debug_mv;
    #define FF_DEBUG_VIS_MV_P_FOR  0x00000001 // visualize forward predicted MVs of P-frames
    #define FF_DEBUG_VIS_MV_B_FOR  0x00000002 // visualize forward predicted MVs of B-frames
    #define FF_DEBUG_VIS_MV_B_BACK 0x00000004 // visualize backward predicted MVs of B-frames
    #endif
    
        /**
         * Error recognition; may misdetect some more or less valid parts as errors.
         * - encoding: unused
         * - decoding: Set by user.
         */
        int err_recognition;
    
    /**
     * Verify checksums embedded in the bitstream (could be of either encoded or
     * decoded data, depending on the codec) and print an error message on mismatch.
     * If AV_EF_EXPLODE is also set, a mismatching checksum will result in the
     * decoder returning an error.
     */
    #define AV_EF_CRCCHECK  (1<<0)
    #define AV_EF_BITSTREAM (1<<1)          ///< detect bitstream specification deviations
    #define AV_EF_BUFFER    (1<<2)          ///< detect improper bitstream length
    #define AV_EF_EXPLODE   (1<<3)          ///< abort decoding on minor error detection
    
    #define AV_EF_IGNORE_ERR (1<<15)        ///< ignore errors and continue
    #define AV_EF_CAREFUL    (1<<16)        ///< consider things that violate the spec, are fast to calculate and have not been seen in the wild as errors
    #define AV_EF_COMPLIANT  (1<<17)        ///< consider all spec non compliances as errors
    #define AV_EF_AGGRESSIVE (1<<18)        ///< consider things that a sane encoder should not do as an error
    
    
        /**
         * opaque 64-bit number (generally a PTS) that will be reordered and
         * output in AVFrame.reordered_opaque
         * - encoding: unused
         * - decoding: Set by user.
         */
        int64_t reordered_opaque;
    
        /**
         * Hardware accelerator in use
         * - encoding: unused.
         * - decoding: Set by libavcodec
         */
        struct AVHWAccel *hwaccel;
    
        /**
         * Hardware accelerator context.
         * For some hardware accelerators, a global context needs to be
         * provided by the user. In that case, this holds display-dependent
         * data FFmpeg cannot instantiate itself. Please refer to the
         * FFmpeg HW accelerator documentation to know how to fill this
         * is. e.g. for VA API, this is a struct vaapi_context.
         * - encoding: unused
         * - decoding: Set by user
         */
        void *hwaccel_context;
    
        /**
         * error
         * - encoding: Set by libavcodec if flags & AV_CODEC_FLAG_PSNR.
         * - decoding: unused
         */
        uint64_t error[AV_NUM_DATA_POINTERS];
    
        /**
         * DCT algorithm, see FF_DCT_* below
         * - encoding: Set by user.
         * - decoding: unused
         */
        int dct_algo;
    #define FF_DCT_AUTO    0
    #define FF_DCT_FASTINT 1
    #define FF_DCT_INT     2
    #define FF_DCT_MMX     3
    #define FF_DCT_ALTIVEC 5
    #define FF_DCT_FAAN    6
    
        /**
         * IDCT algorithm, see FF_IDCT_* below.
         * - encoding: Set by user.
         * - decoding: Set by user.
         */
        int idct_algo;
    #define FF_IDCT_AUTO          0
    #define FF_IDCT_INT           1
    #define FF_IDCT_SIMPLE        2
    #define FF_IDCT_SIMPLEMMX     3
    #define FF_IDCT_ARM           7
    #define FF_IDCT_ALTIVEC       8
    #if FF_API_ARCH_SH4
    #define FF_IDCT_SH4           9
    #endif
    #define FF_IDCT_SIMPLEARM     10
    #if FF_API_UNUSED_MEMBERS
    #define FF_IDCT_IPP           13
    #endif /* FF_API_UNUSED_MEMBERS */
    #define FF_IDCT_XVID          14
    #if FF_API_IDCT_XVIDMMX
    #define FF_IDCT_XVIDMMX       14
    #endif /* FF_API_IDCT_XVIDMMX */
    #define FF_IDCT_SIMPLEARMV5TE 16
    #define FF_IDCT_SIMPLEARMV6   17
    #if FF_API_ARCH_SPARC
    #define FF_IDCT_SIMPLEVIS     18
    #endif
    #define FF_IDCT_FAAN          20
    #define FF_IDCT_SIMPLENEON    22
    #if FF_API_ARCH_ALPHA
    #define FF_IDCT_SIMPLEALPHA   23
    #endif
    #define FF_IDCT_SIMPLEAUTO    128
    
        /**
         * bits per sample/pixel from the demuxer (needed for huffyuv).
         * - encoding: Set by libavcodec.
         * - decoding: Set by user.
         */
         int bits_per_coded_sample;
    
        /**
         * Bits per sample/pixel of internal libavcodec pixel/sample format.
         * - encoding: set by user.
         * - decoding: set by libavcodec.
         */
        int bits_per_raw_sample;
    
    #if FF_API_LOWRES
        /**
         * low resolution decoding, 1-> 1/2 size, 2->1/4 size
         * - encoding: unused
         * - decoding: Set by user.
         * Code outside libavcodec should access this field using:
         * av_codec_{get,set}_lowres(avctx)
         */
         int lowres;
    #endif
    
    #if FF_API_CODED_FRAME
        /**
         * the picture in the bitstream
         * - encoding: Set by libavcodec.
         * - decoding: unused
         *
         * @deprecated use the quality factor packet side data instead
         */
        attribute_deprecated AVFrame *coded_frame;
    #endif
    
        /**
         * thread count
         * is used to decide how many independent tasks should be passed to execute()
         * - encoding: Set by user.
         * - decoding: Set by user.
         */
        int thread_count;
    
        /**
         * Which multithreading methods to use.
         * Use of FF_THREAD_FRAME will increase decoding delay by one frame per thread,
         * so clients which cannot provide future frames should not use it.
         *
         * - encoding: Set by user, otherwise the default is used.
         * - decoding: Set by user, otherwise the default is used.
         */
        int thread_type;
    #define FF_THREAD_FRAME   1 ///< Decode more than one frame at once
    #define FF_THREAD_SLICE   2 ///< Decode more than one part of a single frame at once
    
        /**
         * Which multithreading methods are in use by the codec.
         * - encoding: Set by libavcodec.
         * - decoding: Set by libavcodec.
         */
        int active_thread_type;
    
        /**
         * Set by the client if its custom get_buffer() callback can be called
         * synchronously from another thread, which allows faster multithreaded decoding.
         * draw_horiz_band() will be called from other threads regardless of this setting.
         * Ignored if the default get_buffer() is used.
         * - encoding: Set by user.
         * - decoding: Set by user.
         */
        int thread_safe_callbacks;
    
        /**
         * The codec may call this to execute several independent things.
         * It will return only after finishing all tasks.
         * The user may replace this with some multithreaded implementation,
         * the default implementation will execute the parts serially.
         * @param count the number of things to execute
         * - encoding: Set by libavcodec, user can override.
         * - decoding: Set by libavcodec, user can override.
         */
        int (*execute)(struct AVCodecContext *c, int (*func)(struct AVCodecContext *c2, void *arg), void *arg2, int *ret, int count, int size);
    
        /**
         * The codec may call this to execute several independent things.
         * It will return only after finishing all tasks.
         * The user may replace this with some multithreaded implementation,
         * the default implementation will execute the parts serially.
         * Also see avcodec_thread_init and e.g. the --enable-pthread configure option.
         * @param c context passed also to func
         * @param count the number of things to execute
         * @param arg2 argument passed unchanged to func
         * @param ret return values of executed functions, must have space for "count" values. May be NULL.
         * @param func function that will be called count times, with jobnr from 0 to count-1.
         *             threadnr will be in the range 0 to c->thread_count-1 < MAX_THREADS and so that no
         *             two instances of func executing at the same time will have the same threadnr.
         * @return always 0 currently, but code should handle a future improvement where when any call to func
         *         returns < 0 no further calls to func may be done and < 0 is returned.
         * - encoding: Set by libavcodec, user can override.
         * - decoding: Set by libavcodec, user can override.
         */
        int (*execute2)(struct AVCodecContext *c, int (*func)(struct AVCodecContext *c2, void *arg, int jobnr, int threadnr), void *arg2, int *ret, int count);
    
        /**
         * noise vs. sse weight for the nsse comparison function
         * - encoding: Set by user.
         * - decoding: unused
         */
         int nsse_weight;
    
        /**
         * profile
         * - encoding: Set by user.
         * - decoding: Set by libavcodec.
         */
         int profile;
    #define FF_PROFILE_UNKNOWN -99
    #define FF_PROFILE_RESERVED -100
    
    #define FF_PROFILE_AAC_MAIN 0
    #define FF_PROFILE_AAC_LOW  1
    #define FF_PROFILE_AAC_SSR  2
    #define FF_PROFILE_AAC_LTP  3
    #define FF_PROFILE_AAC_HE   4
    #define FF_PROFILE_AAC_HE_V2 28
    #define FF_PROFILE_AAC_LD   22
    #define FF_PROFILE_AAC_ELD  38
    #define FF_PROFILE_MPEG2_AAC_LOW 128
    #define FF_PROFILE_MPEG2_AAC_HE  131
    
    #define FF_PROFILE_DTS         20
    #define FF_PROFILE_DTS_ES      30
    #define FF_PROFILE_DTS_96_24   40
    #define FF_PROFILE_DTS_HD_HRA  50
    #define FF_PROFILE_DTS_HD_MA   60
    #define FF_PROFILE_DTS_EXPRESS 70
    
    #define FF_PROFILE_MPEG2_422    0
    #define FF_PROFILE_MPEG2_HIGH   1
    #define FF_PROFILE_MPEG2_SS     2
    #define FF_PROFILE_MPEG2_SNR_SCALABLE  3
    #define FF_PROFILE_MPEG2_MAIN   4
    #define FF_PROFILE_MPEG2_SIMPLE 5
    
    #define FF_PROFILE_H264_CONSTRAINED  (1<<9)  // 8+1; constraint_set1_flag
    #define FF_PROFILE_H264_INTRA        (1<<11) // 8+3; constraint_set3_flag
    
    #define FF_PROFILE_H264_BASELINE             66
    #define FF_PROFILE_H264_CONSTRAINED_BASELINE (66|FF_PROFILE_H264_CONSTRAINED)
    #define FF_PROFILE_H264_MAIN                 77
    #define FF_PROFILE_H264_EXTENDED             88
    #define FF_PROFILE_H264_HIGH                 100
    #define FF_PROFILE_H264_HIGH_10              110
    #define FF_PROFILE_H264_HIGH_10_INTRA        (110|FF_PROFILE_H264_INTRA)
    #define FF_PROFILE_H264_HIGH_422             122
    #define FF_PROFILE_H264_HIGH_422_INTRA       (122|FF_PROFILE_H264_INTRA)
    #define FF_PROFILE_H264_HIGH_444             144
    #define FF_PROFILE_H264_HIGH_444_PREDICTIVE  244
    #define FF_PROFILE_H264_HIGH_444_INTRA       (244|FF_PROFILE_H264_INTRA)
    #define FF_PROFILE_H264_CAVLC_444            44
    
    #define FF_PROFILE_VC1_SIMPLE   0
    #define FF_PROFILE_VC1_MAIN     1
    #define FF_PROFILE_VC1_COMPLEX  2
    #define FF_PROFILE_VC1_ADVANCED 3
    
    #define FF_PROFILE_MPEG4_SIMPLE                     0
    #define FF_PROFILE_MPEG4_SIMPLE_SCALABLE            1
    #define FF_PROFILE_MPEG4_CORE                       2
    #define FF_PROFILE_MPEG4_MAIN                       3
    #define FF_PROFILE_MPEG4_N_BIT                      4
    #define FF_PROFILE_MPEG4_SCALABLE_TEXTURE           5
    #define FF_PROFILE_MPEG4_SIMPLE_FACE_ANIMATION      6
    #define FF_PROFILE_MPEG4_BASIC_ANIMATED_TEXTURE     7
    #define FF_PROFILE_MPEG4_HYBRID                     8
    #define FF_PROFILE_MPEG4_ADVANCED_REAL_TIME         9
    #define FF_PROFILE_MPEG4_CORE_SCALABLE             10
    #define FF_PROFILE_MPEG4_ADVANCED_CODING           11
    #define FF_PROFILE_MPEG4_ADVANCED_CORE             12
    #define FF_PROFILE_MPEG4_ADVANCED_SCALABLE_TEXTURE 13
    #define FF_PROFILE_MPEG4_SIMPLE_STUDIO             14
    #define FF_PROFILE_MPEG4_ADVANCED_SIMPLE           15
    
    #define FF_PROFILE_JPEG2000_CSTREAM_RESTRICTION_0   1
    #define FF_PROFILE_JPEG2000_CSTREAM_RESTRICTION_1   2
    #define FF_PROFILE_JPEG2000_CSTREAM_NO_RESTRICTION  32768
    #define FF_PROFILE_JPEG2000_DCINEMA_2K              3
    #define FF_PROFILE_JPEG2000_DCINEMA_4K              4
    
    #define FF_PROFILE_VP9_0                            0
    #define FF_PROFILE_VP9_1                            1
    #define FF_PROFILE_VP9_2                            2
    #define FF_PROFILE_VP9_3                            3
    
    #define FF_PROFILE_HEVC_MAIN                        1
    #define FF_PROFILE_HEVC_MAIN_10                     2
    #define FF_PROFILE_HEVC_MAIN_STILL_PICTURE          3
    #define FF_PROFILE_HEVC_REXT                        4
    
        /**
         * level
         * - encoding: Set by user.
         * - decoding: Set by libavcodec.
         */
         int level;
    #define FF_LEVEL_UNKNOWN -99
    
        /**
         * Skip loop filtering for selected frames.
         * - encoding: unused
         * - decoding: Set by user.
         */
        enum AVDiscard skip_loop_filter;
    
        /**
         * Skip IDCT/dequantization for selected frames.
         * - encoding: unused
         * - decoding: Set by user.
         */
        enum AVDiscard skip_idct;
    
        /**
         * Skip decoding for selected frames.
         * - encoding: unused
         * - decoding: Set by user.
         */
        enum AVDiscard skip_frame;
    
        /**
         * Header containing style information for text subtitles.
         * For SUBTITLE_ASS subtitle type, it should contain the whole ASS
         * [Script Info] and [V4+ Styles] section, plus the [Events] line and
         * the Format line following. It shouldn't include any Dialogue line.
         * - encoding: Set/allocated/freed by user (before avcodec_open2())
         * - decoding: Set/allocated/freed by libavcodec (by avcodec_open2())
         */
        uint8_t *subtitle_header;
        int subtitle_header_size;
    
    #if FF_API_ERROR_RATE
        /**
         * @deprecated use the 'error_rate' private AVOption of the mpegvideo
         * encoders
         */
        attribute_deprecated
        int error_rate;
    #endif
    
    #if FF_API_VBV_DELAY
        /**
         * VBV delay coded in the last frame (in periods of a 27 MHz clock).
         * Used for compliant TS muxing.
         * - encoding: Set by libavcodec.
         * - decoding: unused.
         * @deprecated this value is now exported as a part of
         * AV_PKT_DATA_CPB_PROPERTIES packet side data
         */
        attribute_deprecated
        uint64_t vbv_delay;
    #endif
    
    #if FF_API_SIDEDATA_ONLY_PKT
        /**
         * Encoding only and set by default. Allow encoders to output packets
         * that do not contain any encoded data, only side data.
         *
         * Some encoders need to output such packets, e.g. to update some stream
         * parameters at the end of encoding.
         *
         * @deprecated this field disables the default behaviour and
         *             it is kept only for compatibility.
         */
        attribute_deprecated
        int side_data_only_packets;
    #endif
    
        /**
         * Audio only. The number of "priming" samples (padding) inserted by the
         * encoder at the beginning of the audio. I.e. this number of leading
         * decoded samples must be discarded by the caller to get the original audio
         * without leading padding.
         *
         * - decoding: unused
         * - encoding: Set by libavcodec. The timestamps on the output packets are
         *             adjusted by the encoder so that they always refer to the
         *             first sample of the data actually contained in the packet,
         *             including any added padding.  E.g. if the timebase is
         *             1/samplerate and the timestamp of the first input sample is
         *             0, the timestamp of the first output packet will be
         *             -initial_padding.
         */
        int initial_padding;
    
        /**
         * - decoding: For codecs that store a framerate value in the compressed
         *             bitstream, the decoder may export it here. { 0, 1} when
         *             unknown.
         * - encoding: May be used to signal the framerate of CFR content to an
         *             encoder.
         */
        AVRational framerate;
    
        /**
         * Nominal unaccelerated pixel format, see AV_PIX_FMT_xxx.
         * - encoding: unused.
         * - decoding: Set by libavcodec before calling get_format()
         */
        enum AVPixelFormat sw_pix_fmt;
    
        /**
         * Timebase in which pkt_dts/pts and AVPacket.dts/pts are.
         * Code outside libavcodec should access this field using:
         * av_codec_{get,set}_pkt_timebase(avctx)
         * - encoding unused.
         * - decoding set by user.
         */
        AVRational pkt_timebase;
    
        /**
         * AVCodecDescriptor
         * Code outside libavcodec should access this field using:
         * av_codec_{get,set}_codec_descriptor(avctx)
         * - encoding: unused.
         * - decoding: set by libavcodec.
         */
        const AVCodecDescriptor *codec_descriptor;
    
    #if !FF_API_LOWRES
        /**
         * low resolution decoding, 1-> 1/2 size, 2->1/4 size
         * - encoding: unused
         * - decoding: Set by user.
         * Code outside libavcodec should access this field using:
         * av_codec_{get,set}_lowres(avctx)
         */
         int lowres;
    #endif
    
        /**
         * Current statistics for PTS correction.
         * - decoding: maintained and used by libavcodec, not intended to be used by user apps
         * - encoding: unused
         */
        int64_t pts_correction_num_faulty_pts; /// Number of incorrect PTS values so far
        int64_t pts_correction_num_faulty_dts; /// Number of incorrect DTS values so far
        int64_t pts_correction_last_pts;       /// PTS of the last frame
        int64_t pts_correction_last_dts;       /// DTS of the last frame
    
        /**
         * Character encoding of the input subtitles file.
         * - decoding: set by user
         * - encoding: unused
         */
        char *sub_charenc;
    
        /**
         * Subtitles character encoding mode. Formats or codecs might be adjusting
         * this setting (if they are doing the conversion themselves for instance).
         * - decoding: set by libavcodec
         * - encoding: unused
         */
        int sub_charenc_mode;
    #define FF_SUB_CHARENC_MODE_DO_NOTHING  -1  ///< do nothing (demuxer outputs a stream supposed to be already in UTF-8, or the codec is bitmap for instance)
    #define FF_SUB_CHARENC_MODE_AUTOMATIC    0  ///< libavcodec will select the mode itself
    #define FF_SUB_CHARENC_MODE_PRE_DECODER  1  ///< the AVPacket data needs to be recoded to UTF-8 before being fed to the decoder, requires iconv
    
        /**
         * Skip processing alpha if supported by codec.
         * Note that if the format uses pre-multiplied alpha (common with VP6,
         * and recommended due to better video quality/compression)
         * the image will look as if alpha-blended onto a black background.
         * However for formats that do not use pre-multiplied alpha
         * there might be serious artefacts (though e.g. libswscale currently
         * assumes pre-multiplied alpha anyway).
         * Code outside libavcodec should access this field using AVOptions
         *
         * - decoding: set by user
         * - encoding: unused
         */
        int skip_alpha;
    
        /**
         * Number of samples to skip after a discontinuity
         * - decoding: unused
         * - encoding: set by libavcodec
         */
        int seek_preroll;
    
    #if !FF_API_DEBUG_MV
        /**
         * debug motion vectors
         * Code outside libavcodec should access this field using AVOptions
         * - encoding: Set by user.
         * - decoding: Set by user.
         */
        int debug_mv;
    #define FF_DEBUG_VIS_MV_P_FOR  0x00000001 //visualize forward predicted MVs of P frames
    #define FF_DEBUG_VIS_MV_B_FOR  0x00000002 //visualize forward predicted MVs of B frames
    #define FF_DEBUG_VIS_MV_B_BACK 0x00000004 //visualize backward predicted MVs of B frames
    #endif
    
        /**
         * custom intra quantization matrix
         * Code outside libavcodec should access this field using av_codec_g/set_chroma_intra_matrix()
         * - encoding: Set by user, can be NULL.
         * - decoding: unused.
         */
        uint16_t *chroma_intra_matrix;
    
        /**
         * dump format separator.
         * can be ", " or "
          " or anything else
         * Code outside libavcodec should access this field using AVOptions
         * (NO direct access).
         * - encoding: Set by user.
         * - decoding: Set by user.
         */
        uint8_t *dump_separator;
    
        /**
         * ',' separated list of allowed decoders.
         * If NULL then all are allowed
         * - encoding: unused
         * - decoding: set by user through AVOPtions (NO direct access)
         */
        char *codec_whitelist;
    
        /*
         * Properties of the stream that gets decoded
         * To be accessed through av_codec_get_properties() (NO direct access)
         * - encoding: unused
         * - decoding: set by libavcodec
         */
        unsigned properties;
    #define FF_CODEC_PROPERTY_LOSSLESS        0x00000001
    #define FF_CODEC_PROPERTY_CLOSED_CAPTIONS 0x00000002
    
        /**
         * Additional data associated with the entire coded stream.
         *
         * - decoding: unused
         * - encoding: may be set by libavcodec after avcodec_open2().
         */
        AVPacketSideData *coded_side_data;
        int            nb_coded_side_data;
    
        /**
         * Encoding only.
         *
         * For hardware encoders configured to use a hwaccel pixel format, this
         * field should be set by the caller to a reference to the AVHWFramesContext
         * describing input frames. AVHWFramesContext.format must be equal to
         * AVCodecContext.pix_fmt.
         *
         * This field should be set before avcodec_open2() is called and is
         * afterwards owned and managed by libavcodec.
         */
        AVBufferRef *hw_frames_ctx;
    
        /**
         * Control the form of AVSubtitle.rects[N]->ass
         * - decoding: set by user
         * - encoding: unused
         */
        int sub_text_format;
    #define FF_SUB_TEXT_FMT_ASS              0
    #if FF_API_ASS_TIMING
    #define FF_SUB_TEXT_FMT_ASS_WITH_TIMINGS 1
    #endif
    
    } AVCodecContext;

    int width, height; 视频有关,画面宽高

    int coded_width, coded_height; 码流宽高。不同于width/height,当解码出来帧在裁剪出来前输出时画面

    int gop_size; (group of pictures) GOP画面组大小

    int max_b_frames; B帧最大值

    int has_b_frames; 解码器的帧又一次排序缓冲区的大小。MPEG-2 1个IBP

    int sample_rate; 音频採样率

    int channels; 声道数目

    enum AVSampleFormat sample_fmt; 音频採样格式,枚举类型

    enum AVSampleFormat {  
        AV_SAMPLE_FMT_NONE = -1,  
        AV_SAMPLE_FMT_U8,          ///< unsigned 8 bits  
        AV_SAMPLE_FMT_S16,         ///< signed 16 bits  
        AV_SAMPLE_FMT_S32,         ///< signed 32 bits  
        AV_SAMPLE_FMT_FLT,         ///< float  
        AV_SAMPLE_FMT_DBL,         ///< double  
    
        AV_SAMPLE_FMT_U8P,         ///< unsigned 8 bits, planar  
        AV_SAMPLE_FMT_S16P,        ///< signed 16 bits, planar  
        AV_SAMPLE_FMT_S32P,        ///< signed 32 bits, planar  
        AV_SAMPLE_FMT_FLTP,        ///< float, planar  
        AV_SAMPLE_FMT_DBLP,        ///< double, planar  
    
        AV_SAMPLE_FMT_NB           ///< Number of sample formats. DO NOT USE if linking dynamically  
    }; 

    int frame_size; 一个音频帧里每一个声道採样数目

    int frame_number; 帧数目。解码时是解码器总解码的帧数目,编码时是编码过的帧数目

    int (*get_buffer2)(struct AVCodecContext *s, AVFrame *frame, int flags);这个回调被调用,当从buffer中得到每帧的数据时,每一个buffer必须使用AVBuffer API进行引用技数

    例如以下属性将被设置在callback回调之前

    • format
    • width, height(视频)
    • sample_rate, channel_layout, nb_samples(音频)
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  • 原文地址:https://www.cnblogs.com/yjbjingcha/p/7276990.html
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