同步音频的原理可以参考：http://dranger.com/ffmpeg/tutorial05.html 本文是在 [原]如何在Android用FFmpeg+SDL2.0之同步视频 的基础上面继续进行将视频和音频同步到外部时钟的工作，同时也包含了修正音频解码的问题。
/* * SDL_Lesson.c * * Created on: Aug 12, 2014 * Author: clarck */ #include <jni.h> #include <android/native_window_jni.h> #include "SDL.h" #include "SDL_thread.h" #include "SDL_events.h" #include "../include/logger.h" #include "../ffmpeg/include/libavcodec/avcodec.h" #include "../ffmpeg/include/libavformat/avformat.h" #include "../ffmpeg/include/libavutil/pixfmt.h" #include "../ffmpeg/include/libswscale/swscale.h" #include "../ffmpeg/include/libswresample/swresample.h" #define SDL_AUDIO_BUFFER_SIZE 1024 #define MAX_AUDIOQ_SIZE (5 * 16 * 1024) #define MAX_VIDEOQ_SIZE (5 * 256 * 1024) #define AV_SYNC_THRESHOLD 0.01 #define AV_NOSYNC_THRESHOLD 10.0 #define SAMPLE_CORRECTION_PERCENT_MAX 10 #define AUDIO_DIFF_AVG_NB 20 #define FF_ALLOC_EVENT (SDL_USEREVENT) #define FF_REFRESH_EVENT (SDL_USEREVENT + 1) #define FF_QUIT_EVENT (SDL_USEREVENT + 2) #define VIDEO_PICTURE_QUEUE_SIZE 1 #define DEFAULT_AV_SYNC_TYPE AV_SYNC_VIDEO_MASTER #define AVCODEC_MAX_AUDIO_FRAME_SIZE 192000 // 1 second of 48khz 32bit audio typedef struct PacketQueue { AVPacketList *first_pkt, *last_pkt; int nb_packets; int size; SDL_mutex *mutex; SDL_cond *cond; } PacketQueue; typedef struct VideoPicture { SDL_Window *screen; SDL_Renderer *renderer; SDL_Texture *bmp; AVFrame* rawdata; int width, height; /*source height & width*/ int allocated; double pts; } VideoPicture; typedef struct VideoState { char filename[1024]; AVFormatContext *ic; int videoStream, audioStream; AVStream *audio_st; AVFrame *audio_frame; PacketQueue audioq; unsigned int audio_buf_size; unsigned int audio_buf_index; AVPacket audio_pkt; uint8_t *audio_pkt_data; int audio_pkt_size; uint8_t *audio_buf; DECLARE_ALIGNED(16,uint8_t,audio_buf2) [AVCODEC_MAX_AUDIO_FRAME_SIZE * 4]; enum AVSampleFormat audio_src_fmt; enum AVSampleFormat audio_tgt_fmt; int audio_src_channels; int audio_tgt_channels; int64_t audio_src_channel_layout; int64_t audio_tgt_channel_layout; int audio_src_freq; int audio_tgt_freq; struct SwrContext *swr_ctx; AVStream *video_st; PacketQueue videoq; VideoPicture pictq[VIDEO_PICTURE_QUEUE_SIZE]; int pictq_size, pictq_rindex, pictq_windex; SDL_mutex *pictq_mutex; SDL_cond *pictq_cond; SDL_Thread *parse_tid; SDL_Thread *audio_tid; SDL_Thread *video_tid; AVIOContext *io_ctx; struct SwsContext *sws_ctx; double audio_clock; int av_sync_type; double external_clock;/*external clock base*/ int64_t external_clock_time; int audio_hw_buf_size; double audio_diff_cum;/*used of AV difference average computation*/ double audio_diff_avg_coef; double audio_diff_threshold; int audio_diff_avg_count; double frame_timer; double frame_last_pts; double frame_last_delay; double video_current_pts; ///<current displayed pts (different from video_clock if frame fifos are used) int64_t video_current_pts_time; ///<time (av_gettime) at which we updated video_current_pts - used to have running video pts double video_clock; ///<pts of last decoded frame / predicted pts of next decoded frame int quit; } VideoState; enum { AV_SYNC_AUDIO_MASTER, AV_SYNC_VIDEO_MASTER, AV_SYNC_EXTERNAL_MASTER, }; VideoState *global_video_state; void packet_queue_init(PacketQueue *q) { memset(q, 0, sizeof(PacketQueue)); q->mutex = SDL_CreateMutex(); q->cond = SDL_CreateCond(); } int packet_queue_put(PacketQueue *q, AVPacket *pkt) { AVPacketList *pkt1; pkt1 = (AVPacketList *) av_malloc(sizeof(AVPacketList)); if (!pkt1) { return -1; } pkt1->pkt = *pkt; pkt1->next = NULL; SDL_LockMutex(q->mutex); if (!q->last_pkt) { q->first_pkt = pkt1; } else { q->last_pkt->next = pkt1; } q->last_pkt = pkt1; q->nb_packets++; q->size += pkt1->pkt.size; SDL_CondSignal(q->cond); SDL_UnlockMutex(q->mutex); return 0; } static int packet_queue_get(PacketQueue *q, AVPacket *pkt, int block) { AVPacketList *pkt1; int ret; SDL_LockMutex(q->mutex); for (;;) { if (global_video_state->quit) { ret = -1; break; } pkt1 = q->first_pkt; if (pkt1) { q->first_pkt = pkt1->next; if (!q->first_pkt) { q->last_pkt = NULL; } q->nb_packets--; q->size -= pkt1->pkt.size; *pkt = pkt1->pkt; av_free(pkt1); ret = 1; break; } else if (!block) { ret = 0; break; } else { SDL_CondWait(q->cond, q->mutex); } } SDL_UnlockMutex(q->mutex); return ret; } double get_audio_clock(VideoState *is) { double pts; int hw_buf_size, bytes_per_sec, n; pts = is->audio_clock; /* maintained in the audio thread */ hw_buf_size = is->audio_buf_size - is->audio_buf_index; bytes_per_sec = 0; n = is->audio_st->codec->channels * 2; if (is->audio_st) { bytes_per_sec = is->audio_st->codec->sample_rate * n; } if (bytes_per_sec) { pts -= (double) hw_buf_size / bytes_per_sec; } return pts; } double get_video_clock(VideoState *is) { double delta; delta = (av_gettime() - is->video_current_pts_time) / 1000000.0; return is->video_current_pts + delta; } double get_external_clock(VideoState *is) { return av_gettime() / 1000000.0; } double get_master_clock(VideoState *is) { if (is->av_sync_type == AV_SYNC_VIDEO_MASTER) { return get_video_clock(is); } else if (is->av_sync_type == AV_SYNC_AUDIO_MASTER) { return get_audio_clock(is); } else { return get_external_clock(is); } } /* Add or subtract samples to get a better sync, return new audio buffer size */ int synchronize_audio(VideoState *is, short *samples, int samples_size, double pts) { int n; double ref_clock; n = 2 * is->audio_st->codec->channels; if (is->av_sync_type != AV_SYNC_AUDIO_MASTER) { double diff, avg_diff; int wanted_size, min_size, max_size; //int nb_samples; ref_clock = get_master_clock(is); diff = get_audio_clock(is) - ref_clock; if (diff < AV_NOSYNC_THRESHOLD) { // accumulate the diffs is->audio_diff_cum = diff + is->audio_diff_avg_coef * is->audio_diff_cum; if (is->audio_diff_avg_count < AUDIO_DIFF_AVG_NB) { is->audio_diff_avg_count++; } else { avg_diff = is->audio_diff_cum * (1.0 - is->audio_diff_avg_coef); if (fabs(avg_diff) >= is->audio_diff_threshold) { wanted_size = samples_size + ((int) (diff * is->audio_st->codec->sample_rate) * n); min_size = samples_size * ((100 - SAMPLE_CORRECTION_PERCENT_MAX) / 100); max_size = samples_size * ((100 + SAMPLE_CORRECTION_PERCENT_MAX) / 100); if (wanted_size < min_size) { wanted_size = min_size; } else if (wanted_size > max_size) { wanted_size = max_size; } if (wanted_size < samples_size) { /* remove samples */ samples_size = wanted_size; } else if (wanted_size > samples_size) { uint8_t *samples_end, *q; int nb; /* add samples by copying final sample*/ nb = (samples_size - wanted_size); samples_end = (uint8_t *) samples + samples_size - n; q = samples_end + n; while (nb > 0) { memcpy(q, samples_end, n); q += n; nb -= n; } samples_size = wanted_size; } } } } else { /* difference is TOO big; reset diff stuff */ is->audio_diff_avg_count = 0; is->audio_diff_cum = 0; } } return samples_size; } int audio_decode_frame(VideoState *is, double *pts_ptr) { int len1, len2, decoded_data_size; AVPacket *pkt = &is->audio_pkt; int got_frame = 0; int64_t dec_channel_layout; int wanted_nb_samples, resampled_data_size, n; double pts; for (;;) { while (is->audio_pkt_size > 0) { if (!is->audio_frame) { if (!(is->audio_frame = avcodec_alloc_frame())) { return AVERROR(ENOMEM); } } else avcodec_get_frame_defaults(is->audio_frame); len1 = avcodec_decode_audio4(is->audio_st->codec, is->audio_frame, &got_frame, pkt); if (len1 < 0) { // error, skip the frame is->audio_pkt_size = 0; break; } is->audio_pkt_data += len1; is->audio_pkt_size -= len1; if (!got_frame) continue; /* 计算解码出来的桢需要的缓冲大小 */ decoded_data_size = av_samples_get_buffer_size(NULL, is->audio_frame->channels, is->audio_frame->nb_samples, is->audio_frame->format, 1); dec_channel_layout = (is->audio_frame->channel_layout && is->audio_frame->channels == av_get_channel_layout_nb_channels( is->audio_frame->channel_layout)) ? is->audio_frame->channel_layout : av_get_default_channel_layout( is->audio_frame->channels); wanted_nb_samples = is->audio_frame->nb_samples; if (is->audio_frame->format != is->audio_src_fmt || dec_channel_layout != is->audio_src_channel_layout || is->audio_frame->sample_rate != is->audio_src_freq || (wanted_nb_samples != is->audio_frame->nb_samples && !is->swr_ctx)) { if (is->swr_ctx) swr_free(&is->swr_ctx); is->swr_ctx = swr_alloc_set_opts(NULL, is->audio_tgt_channel_layout, is->audio_tgt_fmt, is->audio_tgt_freq, dec_channel_layout, is->audio_frame->format, is->audio_frame->sample_rate, 0, NULL); if (!is->swr_ctx || swr_init(is->swr_ctx) < 0) { fprintf(stderr, "swr_init() failed "); break; } is->audio_src_channel_layout = dec_channel_layout; is->audio_src_channels = is->audio_st->codec->channels; is->audio_src_freq = is->audio_st->codec->sample_rate; is->audio_src_fmt = is->audio_st->codec->sample_fmt; } /* 这里我们可以对采样数进行调整，增加或者减少，一般可以用来做声画同步 */ if (is->swr_ctx) { const uint8_t **in = (const uint8_t **) is->audio_frame->extended_data; uint8_t *out[] = { is->audio_buf2 }; if (wanted_nb_samples != is->audio_frame->nb_samples) { if (swr_set_compensation(is->swr_ctx, (wanted_nb_samples - is->audio_frame->nb_samples) * is->audio_tgt_freq / is->audio_frame->sample_rate, wanted_nb_samples * is->audio_tgt_freq / is->audio_frame->sample_rate) < 0) { fprintf(stderr, "swr_set_compensation() failed "); break; } } len2 = swr_convert(is->swr_ctx, out, sizeof(is->audio_buf2) / is->audio_tgt_channels / av_get_bytes_per_sample(is->audio_tgt_fmt), in, is->audio_frame->nb_samples); if (len2 < 0) { fprintf(stderr, "swr_convert() failed "); break; } if (len2 == sizeof(is->audio_buf2) / is->audio_tgt_channels / av_get_bytes_per_sample(is->audio_tgt_fmt)) { fprintf(stderr, "warning: audio buffer is probably too small "); swr_init(is->swr_ctx); } is->audio_buf = is->audio_buf2; resampled_data_size = len2 * is->audio_tgt_channels * av_get_bytes_per_sample(is->audio_tgt_fmt); } else { resampled_data_size = decoded_data_size; is->audio_buf = is->audio_frame->data[0]; } pts = is->audio_clock; *pts_ptr = pts; n = 2 * is->audio_st->codec->channels; is->audio_clock += (double) resampled_data_size / (double) (n * is->audio_st->codec->sample_rate); // We have data, return it and come back for more later return resampled_data_size; } if (pkt->data) av_free_packet(pkt); memset(pkt, 0, sizeof(*pkt)); if (is->quit) return -1; if (packet_queue_get(&is->audioq, pkt, 1) < 0) return -1; is->audio_pkt_data = pkt->data; is->audio_pkt_size = pkt->size; /* if update, update the audio clock w/pts */ if (pkt->pts != AV_NOPTS_VALUE) { is->audio_clock = av_q2d(is->audio_st->time_base) * pkt->pts; } } return 0; } void audio_callback(void *userdata, Uint8 *stream, int len) { VideoState *is = (VideoState *) userdata; int len1, audio_data_size; double pts; /* len是由SDL传入的SDL缓冲区的大小，如果这个缓冲未满，我们就一直往里填充数据 */ while (len > 0) { /* audio_buf_index 和 audio_buf_size 标示我们自己用来放置解码出来的数据的缓冲区，*/ /* 这些数据待copy到SDL缓冲区， 当audio_buf_index >= audio_buf_size的时候意味着我*/ /* 们的缓冲为空，没有数据可供copy，这时候需要调用audio_decode_frame来解码出更 /* 多的桢数据 */ if (is->audio_buf_index >= is->audio_buf_size) { audio_data_size = audio_decode_frame(is, &pts); /* audio_data_size < 0 标示没能解码出数据，我们默认播放静音 */ if (audio_data_size < 0) { /* silence */ is->audio_buf_size = 1024; /* 清零，静音 */ memset(is->audio_buf, 0, is->audio_buf_size); } else { audio_data_size = synchronize_audio(is, (int16_t *) is->audio_buf, audio_data_size, pts); is->audio_buf_size = audio_data_size; } is->audio_buf_index = 0; } /* 查看stream可用空间，决定一次copy多少数据，剩下的下次继续copy */ len1 = is->audio_buf_size - is->audio_buf_index; if (len1 > len) { len1 = len; } memcpy(stream, (uint8_t *) is->audio_buf + is->audio_buf_index, len1); len -= len1; stream += len1; is->audio_buf_index += len1; } } static Uint32 sdl_refresh_timer_cb(Uint32 interval, void *opaque) { SDL_Event event; event.type = FF_REFRESH_EVENT; event.user.data1 = opaque; SDL_PushEvent(&event); return 0; } static void schedule_refresh(VideoState *is, int delay) { SDL_AddTimer(delay, sdl_refresh_timer_cb, is); } int decode_interrupt_cb(void *opaque) { return (global_video_state && global_video_state->quit); } void video_display(VideoState *is) { SDL_Rect rect; VideoPicture *vp; float aspect_ratio; vp = &is->pictq[is->pictq_rindex]; if (vp->bmp) { if (is->video_st->codec->sample_aspect_ratio.num == 0) { aspect_ratio = 0; } else { aspect_ratio = av_q2d(is->video_st->codec->sample_aspect_ratio) * is->video_st->codec->width / is->video_st->codec->height; } if (aspect_ratio <= 0.0) { aspect_ratio = (float) is->video_st->codec->width / (float) is->video_st->codec->height; } rect.x = 0; rect.y = 0; rect.w = vp->width; rect.h = vp->height; SDL_UpdateYUVTexture(vp->bmp, &rect, vp->rawdata->data[0], vp->rawdata->linesize[0], vp->rawdata->data[1], vp->rawdata->linesize[1], vp->rawdata->data[2], vp->rawdata->linesize[2]); SDL_RenderClear(vp->renderer); SDL_RenderCopy(vp->renderer, vp->bmp, &rect, &rect); SDL_RenderPresent(vp->renderer); } } void video_refresh_timer(void *userdata) { VideoState *is = (VideoState *) userdata; VideoPicture *vp; double actual_delay, delay, sync_threshold, ref_clock, diff; if (is->video_st) { if (is->pictq_size == 0) { schedule_refresh(is, 1); } else { vp = &is->pictq[is->pictq_rindex]; is->video_current_pts = vp->pts; is->video_current_pts_time = av_gettime(); delay = vp->pts - is->frame_last_pts; /* the pts from last time */ if (delay <= 0 || delay >= 1.0) { /* if incorrect delay, use previous one */ delay = is->frame_last_delay; } /* save for next time */ is->frame_last_delay = delay; is->frame_last_pts = vp->pts; /* update delay to sync to audio */ ref_clock = get_audio_clock(is); diff = vp->pts - ref_clock; /* update delay to sync to audio if not master source */ if (is->av_sync_type != AV_SYNC_VIDEO_MASTER) { ref_clock = get_master_clock(is); diff = vp->pts - ref_clock; /* Skip or repeat the frame. Take delay into account FFPlay still doesn't "know if this is the best guess." */ sync_threshold = (delay > AV_SYNC_THRESHOLD) ? delay : AV_SYNC_THRESHOLD; if (fabs(diff) < AV_NOSYNC_THRESHOLD) { if (diff <= -sync_threshold) { delay = 0; } else if (diff >= sync_threshold) { delay = 2 * delay; } } } is->frame_timer += delay; /* computer the REAL delay */ actual_delay = is->frame_timer - (av_gettime() / 1000000.0); if (actual_delay < 0.010) { /* Really it should skip the picture instead */ actual_delay = 0.010; } schedule_refresh(is, (int) (actual_delay * 1000 + 0.5)); /* show the picture! */ video_display(is); /* update queue for next picture! */ if (++is->pictq_rindex == VIDEO_PICTURE_QUEUE_SIZE) { is->pictq_rindex = 0; } SDL_LockMutex(is->pictq_mutex); is->pictq_size--; SDL_CondSignal(is->pictq_cond); SDL_UnlockMutex(is->pictq_mutex); } } else { schedule_refresh(is, 100); } } void alloc_picture(void *userdata) { VideoState *is = (VideoState *) userdata; VideoPicture *vp; vp = &is->pictq[is->pictq_windex]; if (vp->bmp) { // we already have one make another, bigger/smaller SDL_DestroyTexture(vp->bmp); } if(vp->rawdata) { av_free(vp->rawdata); } // Allocate a place to put our YUV image on that screen vp->screen = SDL_CreateWindow("My Player Window", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, is->video_st->codec->width, is->video_st->codec->height, SDL_WINDOW_FULLSCREEN | SDL_WINDOW_OPENGL); vp->renderer = SDL_CreateRenderer(vp->screen, -1, 0); vp->bmp = SDL_CreateTexture(vp->renderer, SDL_PIXELFORMAT_YV12, SDL_TEXTUREACCESS_STREAMING, is->video_st->codec->width, is->video_st->codec->height); vp->width = is->video_st->codec->width; vp->height = is->video_st->codec->height; AVFrame* pFrameYUV = avcodec_alloc_frame(); if (pFrameYUV == NULL) return; int numBytes = avpicture_get_size(PIX_FMT_YUV420P, vp->width, vp->height); uint8_t* buffer = (uint8_t *) av_malloc(numBytes * sizeof(uint8_t)); avpicture_fill((AVPicture *) pFrameYUV, buffer, PIX_FMT_YUV420P, vp->width, vp->height); vp->rawdata = pFrameYUV; SDL_LockMutex(is->pictq_mutex); vp->allocated = 1; SDL_CondSignal(is->pictq_cond); SDL_UnlockMutex(is->pictq_mutex); } int queue_picture(VideoState *is, AVFrame *pFrame, double pts) { VideoPicture *vp; //int dst_pic_fmt AVPicture pict; /* wait unitl we have space for a new pic */ SDL_LockMutex(is->pictq_mutex); while (is->pictq_size >= VIDEO_PICTURE_QUEUE_SIZE && !is->quit) { SDL_CondWait(is->pictq_cond, is->pictq_mutex); } SDL_UnlockMutex(is->pictq_mutex); if (is->quit) return -1; // windex is set to 0 initially vp = &is->pictq[is->pictq_windex]; /* allocate or resize the buffer ! */ if (!vp->bmp || vp->width != is->video_st->codec->width || vp->height != is->video_st->codec->height) { SDL_Event event; vp->allocated = 0; /* we have to do it in the main thread */ event.type = FF_ALLOC_EVENT; event.user.data1 = is; SDL_PushEvent(&event); /* wait until we have a picture allocated */ SDL_LockMutex(is->pictq_mutex); while (!vp->allocated && !is->quit) { SDL_CondWait(is->pictq_cond, is->pictq_mutex); } } SDL_UnlockMutex(is->pictq_mutex); if (is->quit) { return -1; } /* We have a place to put our picture on the queue */ if (vp->rawdata) { // Convert the image into YUV format that SDL uses sws_scale(is->sws_ctx, (uint8_t const * const *) pFrame->data, pFrame->linesize, 0, is->video_st->codec->height, vp->rawdata->data, vp->rawdata->linesize); vp->pts = pts; /* now we inform our display thread that we have a pic ready */ if (++is->pictq_windex == VIDEO_PICTURE_QUEUE_SIZE) { is->pictq_windex = 0; } SDL_LockMutex(is->pictq_mutex); is->pictq_size++; SDL_UnlockMutex(is->pictq_mutex); } return 0; } double synchronize_video(VideoState *is, AVFrame *src_frame, double pts) { double frame_delay; if (pts != 0) { /* if we have pts, set video clock to it */ is->video_clock = pts; } else { /* if we aren't given a pts, set it to the clock */ pts = is->video_clock; } /* update the video clock */ frame_delay = av_q2d(is->video_st->codec->time_base); /* if we are repeating a frame, adjust clock accordingly */ frame_delay += src_frame->repeat_pict * (frame_delay * 0.5); is->video_clock += frame_delay; return pts; } uint64_t global_video_pkt_pts = AV_NOPTS_VALUE; /* These are called whenever we allocate a frame * buffer. We use this to store the global_pts in * a frame at the time it is allocated. */ int our_get_buffer(struct AVCodecContext *c, AVFrame *pic) { int ret = avcodec_default_get_buffer(c, pic); uint64_t *pts = av_malloc(sizeof(uint64_t)); *pts = global_video_pkt_pts; pic->opaque = pts; return ret; } void our_release_buffer(struct AVCodecContext *c, AVFrame *pic) { if (pic) av_freep(&pic->opaque); avcodec_default_release_buffer(c, pic); } int video_thread(void *arg) { VideoState *is = (VideoState *) arg; AVPacket pkt1, *packet = &pkt1; int frameFinished; AVFrame *pFrame; double pts; pFrame = av_frame_alloc(); for (;;) { if (packet_queue_get(&is->videoq, packet, 1) < 0) { // means we quit getting packets break; } pts = 0; // Save global pts to be stored in pFrame in first call global_video_pkt_pts = packet->pts; // Decode video frame avcodec_decode_video2(is->video_st->codec, pFrame, &frameFinished, packet); if (packet->dts == AV_NOPTS_VALUE && pFrame->opaque && *(uint64_t*) pFrame->opaque != AV_NOPTS_VALUE) { pts = *(uint64_t *) pFrame->opaque; } else if (packet->dts != AV_NOPTS_VALUE) { pts = packet->dts; } else { pts = 0; } pts *= av_q2d(is->video_st->time_base); // Did we get a video frame? if (frameFinished) { pts = synchronize_video(is, pFrame, pts); if (queue_picture(is, pFrame, pts) < 0) { break; } } av_free_packet(packet); } av_free(pFrame); return 0; } int audio_stream_component_open(VideoState *is, int stream_index) { AVFormatContext *ic = is->ic; AVCodecContext *codecCtx; AVCodec *codec; SDL_AudioSpec wanted_spec, spec; int64_t wanted_channel_layout = 0; int wanted_nb_channels; /* SDL支持的声道数为 1, 2, 4, 6 */ /* 后面我们会使用这个数组来纠正不支持的声道数目 */ const int next_nb_channels[] = { 0, 0, 1, 6, 2, 6, 4, 6 }; if (stream_index < 0 || stream_index >= ic->nb_streams) { return -1; } codecCtx = ic->streams[stream_index]->codec; wanted_nb_channels = codecCtx->channels; if (!wanted_channel_layout || wanted_nb_channels != av_get_channel_layout_nb_channels( wanted_channel_layout)) { wanted_channel_layout = av_get_default_channel_layout( wanted_nb_channels); wanted_channel_layout &= ~AV_CH_LAYOUT_STEREO_DOWNMIX; } wanted_spec.channels = av_get_channel_layout_nb_channels( wanted_channel_layout); wanted_spec.freq = codecCtx->sample_rate; if (wanted_spec.freq <= 0 || wanted_spec.channels <= 0) { fprintf(stderr, "Invalid sample rate or channel count! "); return -1; } wanted_spec.format = AUDIO_S16SYS; // 具体含义请查看“SDL宏定义”部分 wanted_spec.silence = 0; // 0指示静音 wanted_spec.samples = SDL_AUDIO_BUFFER_SIZE; // 自定义SDL缓冲区大小 wanted_spec.callback = audio_callback; // 音频解码的关键回调函数 wanted_spec.userdata = is; // 传给上面回调函数的外带数据 /* 打开音频设备，这里使用一个while来循环尝试打开不同的声道数(由上面 */ /* next_nb_channels数组指定）直到成功打开，或者全部失败 */ while (SDL_OpenAudio(&wanted_spec, &spec) < 0) { fprintf(stderr, "SDL_OpenAudio (%d channels): %s ", wanted_spec.channels, SDL_GetError()); wanted_spec.channels = next_nb_channels[FFMIN(7, wanted_spec.channels)]; if (!wanted_spec.channels) { fprintf(stderr, "No more channel combinations to tyu, audio open failed "); return -1; } wanted_channel_layout = av_get_default_channel_layout( wanted_spec.channels); } /* 检查实际使用的配置（保存在spec,由SDL_OpenAudio()填充） */ if (spec.format != AUDIO_S16SYS) { fprintf(stderr, "SDL advised audio format %d is not supported! ", spec.format); return -1; } if (spec.channels != wanted_spec.channels) { wanted_channel_layout = av_get_default_channel_layout(spec.channels); if (!wanted_channel_layout) { fprintf(stderr, "SDL advised channel count %d is not supported! ", spec.channels); return -1; } } is->audio_hw_buf_size = spec.size; /* 把设置好的参数保存到大结构中 */ is->audio_src_fmt = is->audio_tgt_fmt = AV_SAMPLE_FMT_S16; is->audio_src_freq = is->audio_tgt_freq = spec.freq; is->audio_src_channel_layout = is->audio_tgt_channel_layout = wanted_channel_layout; is->audio_src_channels = is->audio_tgt_channels = spec.channels; codec = avcodec_find_decoder(codecCtx->codec_id); if (!codec || (avcodec_open2(codecCtx, codec, NULL) < 0)) { fprintf(stderr, "Unsupported codec! "); return -1; } ic->streams[stream_index]->discard = AVDISCARD_DEFAULT; switch (codecCtx->codec_type) { case AVMEDIA_TYPE_AUDIO: is->audioStream = stream_index; is->audio_st = ic->streams[stream_index]; is->audio_buf_size = 0; is->audio_buf_index = 0; /* averaging filter for audio sync */ is->audio_diff_avg_coef = exp(log(0.01 / AUDIO_DIFF_AVG_NB)); is->audio_diff_avg_count = 0; /* Correct audio only if larger error than this */ is->audio_diff_threshold = 2.0 * SDL_AUDIO_BUFFER_SIZE / codecCtx->sample_rate; memset(&is->audio_pkt, 0, sizeof(is->audio_pkt)); packet_queue_init(&is->audioq); SDL_PauseAudio(0); // 开始播放静音 break; default: break; } return 0; } int video_stream_component_open(VideoState *is, int stream_index) { AVFormatContext *pFormatCtx = is->ic; AVCodecContext *codecCtx; AVCodec *codec; if (stream_index < 0 || stream_index >= pFormatCtx->nb_streams) { return -1; } // Get a pointer to the codec context for the video stream codecCtx = pFormatCtx->streams[stream_index]->codec; codec = avcodec_find_decoder(codecCtx->codec_id); if (!codec || (avcodec_open2(codecCtx, codec, NULL) < 0)) { fprintf(stderr, "Unsupported codec! "); return -1; } switch (codecCtx->codec_type) { case AVMEDIA_TYPE_VIDEO: is->videoStream = stream_index; is->video_st = pFormatCtx->streams[stream_index]; is->sws_ctx = sws_getContext(is->video_st->codec->width, is->video_st->codec->height, is->video_st->codec->pix_fmt, is->video_st->codec->width, is->video_st->codec->height, AV_PIX_FMT_YUV420P, SWS_FAST_BILINEAR, NULL, NULL, NULL); is->frame_timer = (double) av_gettime() / 1000000.0; is->frame_last_delay = 40e-3; is->video_current_pts_time = av_gettime(); packet_queue_init(&is->videoq); is->video_tid = SDL_CreateThread(video_thread, "video_thread", is); codecCtx->get_buffer = our_get_buffer; codecCtx->release_buffer = our_release_buffer; break; default: break; } return 0; } int decode_thread(void *arg) { VideoState *is = (VideoState *) arg; AVFormatContext *pFormatCtx = NULL; AVPacket pkt1, *packet = &pkt1; int video_index = -1; int audio_index = -1; int i; is->videoStream = -1; is->audioStream = -1; AVIOInterruptCB interupt_cb; global_video_state = is; // will interrup blocking functions if we quit! interupt_cb.callback = decode_interrupt_cb; interupt_cb.opaque = is; if (avio_open2(&is->io_ctx, is->filename, 0, &interupt_cb, NULL)) { fprintf(stderr, "Cannot open I/O for %s ", is->filename); return -1; } //Open video file if (avformat_open_input(&pFormatCtx, is->filename, NULL, NULL) != 0) { return -1; //Couldn't open file } is->ic = pFormatCtx; //Retrieve stream infomation if (avformat_find_stream_info(pFormatCtx, NULL) < 0) { return -1; // Couldn't find stream information } //Dump information about file onto standard error av_dump_format(pFormatCtx, 0, is->filename, 0); //Find the first video stream for (i = 0; i < pFormatCtx->nb_streams; i++) { if (pFormatCtx->streams[i]->codec->coder_type == AVMEDIA_TYPE_VIDEO && video_index < 0) { video_index = i; } if (pFormatCtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_AUDIO && audio_index < 0) { audio_index = i; } } if (audio_index >= 0) { /* 所有设置SDL音频流信息的步骤都在这个函数里完成 */ audio_stream_component_open(is, audio_index); } if (video_index >= 0) { video_stream_component_open(is, video_index); } if (is->videoStream < 0 || is->audioStream <= 0) { fprintf(stderr, "%s: could not open codec ", is->filename); goto fail; } //main decode loop /* 读包的主循环， av_read_frame不停的从文件中读取数据包*/ for (;;) { if (is->quit) { break; } //seek stuff goes here /* 这里audioq.size是指队列中的所有数据包带的音频数据的总量或者视频数据总量，并不是包的数量 */ if (is->audioq.size > MAX_AUDIOQ_SIZE || is->videoq.size > MAX_VIDEOQ_SIZE) { SDL_Delay(10); continue; } if (av_read_frame(is->ic, packet) < 0) { if (is->ic->pb->error == 0) { SDL_Delay(100); /* no error; wait for user input */ continue; } else { break; } } // Is this a packet from the video stream? if (packet->stream_index == is->videoStream) { packet_queue_put(&is->videoq, packet); } else if (packet->stream_index == is->audioStream) { packet_queue_put(&is->audioq, packet); } else { av_free_packet(packet); } } /*all done - wait for it*/ while (!is->quit) { SDL_Delay(100); } fail: if (1) { SDL_Event event; event.type = FF_QUIT_EVENT; event.user.data1 = is; SDL_PushEvent(&event); } return 0; } int main(int argc, char *argv[]) { char *filename = argv[1]; SDL_Event event; VideoState *is; is = av_malloc(sizeof(VideoState)); // Register all formats and codecs av_register_all(); if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER)) { fprintf(stderr, "Could not initialize SDL - %s ", SDL_GetError()); exit(1); } av_strlcpy(is->filename, filename, sizeof(is->filename)); is->pictq_mutex = SDL_CreateMutex(); is->pictq_cond = SDL_CreateCond(); schedule_refresh(is, 40); is->av_sync_type = DEFAULT_AV_SYNC_TYPE; is->parse_tid = SDL_CreateThread(decode_thread, "parse_thread", is); if (!is->parse_tid) { av_free(is); return -1; } for (;;) { SDL_WaitEvent(&event); switch (event.type) { case FF_QUIT_EVENT: case SDL_QUIT: SDL_CondSignal(is->audioq.cond); SDL_CondSignal(is->videoq.cond); is->quit = 1; SDL_Quit(); return 0; break; case FF_ALLOC_EVENT: alloc_picture(event.user.data1); break; case FF_REFRESH_EVENT: video_refresh_timer(event.user.data1); break; } } return 0; }