ffmpeg代码实现自定义encoder

1、概述

本文主要讲述如何用ffmpeg代码实现自己的encoder。

2、代码

/*
*本程序主要实现一个自己的encoder并加入到encoder链中去,供api调用
*作者：缪国凯（MK）
*821486004@qq.com
*2015-6-4
*/

#include "stdafx.h"

#ifdef __cplusplus
extern "C"
{
#endif
#include <libavformat/avformat.h>
#include <libavcodec/avcodec.h>
#include <libavutil/pixdesc.h>
#
#ifdef __cplusplus
};
#endif

#pragma comment(lib, "avcodec.lib")
#pragma comment(lib, "avformat.lib")
#pragma comment(lib, "avutil.lib")
//#pragma comment(lib, "avdevice.lib")
//#pragma comment(lib, "avfilter.lib")
//#pragma comment(lib, "postproc.lib")
//#pragma comment(lib, "swresample.lib")
//#pragma comment(lib, "swscale.lib")

static av_cold int mk_encode_init(AVCodecContext *avctx)
{
    const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(avctx->pix_fmt);

    avctx->coded_frame = av_frame_alloc();
    avctx->coded_frame->pict_type = AV_PICTURE_TYPE_I;
    avctx->bits_per_coded_sample = av_get_bits_per_pixel(desc);
    if(!avctx->codec_tag)
        avctx->codec_tag = avcodec_pix_fmt_to_codec_tag(avctx->pix_fmt);
    return 0;
}

static int mk_encode(AVCodecContext *avctx, AVPacket *pkt,
    const AVFrame *frame, int *got_packet)
{
    int ret = avpicture_get_size(avctx->pix_fmt, avctx->width, avctx->height);

    if (ret < 0)
        return ret;

    if (pkt->data == NULL && pkt->size == 0)
    {
        av_new_packet(pkt,ret);
        pkt->size = ret;
    }

//  if ((ret = ff_alloc_packet2(avctx, pkt, ret)) < 0)
//      return ret;

    if ((ret = avpicture_layout((const AVPicture *)frame, avctx->pix_fmt, avctx->width,
        avctx->height, pkt->data, pkt->size)) < 0)
        return ret;

//  if(avctx->codec_tag == AV_RL32("yuv2") && ret > 0 &&
//      avctx->pix_fmt   == AV_PIX_FMT_YUYV422)
//  {
//          int x;
//          for(x = 1; x < avctx->height*avctx->width*2; x += 2)
//              pkt->data[x] ^= 0x80;
//  }
    pkt->flags |= AV_PKT_FLAG_KEY;
    *got_packet = 1;
    return 0;
}

static av_cold int mk_close(AVCodecContext *avctx)
{
    av_frame_free(&avctx->coded_frame);
    return 0;
}

AVCodec ff_mkvideo_encoder = {
    /*.name           = */"mkvideo",
    /*.long_name      = */"mk video",
    /*.type           = */AVMEDIA_TYPE_VIDEO,
    /*.id             = */AV_CODEC_ID_MKVIDEO,
    /*.capabilities = */0,
    /*.supported_framerates = */NULL,
    /*.pix_fmts     = */NULL,
    /*.supported_samplerates = */NULL,
    /*.sample_fmts  = */NULL,
    /*.channel_layouts = */NULL,
    /*.max_lowres       = */0,
    /*.priv_class       = */NULL,
    /*.profiles     = */NULL,
    /*.priv_data_size   = */0,
    /*.next         = */NULL,
    /*.init_thread_copy = */NULL,
    /*.update_thread_context = */NULL,
    /*.defaults     = */NULL,
    /*.init_static_data = */NULL,
    /*.init           = */mk_encode_init,
    /*.encode_sub       = */NULL,
    /*.encode2        = */mk_encode,
    /*.decode           = */NULL,
    /*.close          = */mk_close,
};

void help()
{
    printf("**********************************************
");
    printf("Usage:
");
    printf("    MyMuxer [inputfile] [outputfile] 
");
    printf("
");
    printf("Examples: 
");
    printf("    MyMuxer a.avi a.yuv 
");
    printf("**********************************************
");
}

int _tmain(int argc, _TCHAR* argv[])
{
    if(argc < 3 || (!strcmp(argv[1],"--help")))
    {
        help();
        return 0;
    }

    av_register_all();
    avcodec_register(&ff_mkvideo_encoder);

    AVFormatContext *in_fxt = NULL, *out_fxt = NULL;
    AVStream *out_stream = NULL;
    int video_index = -1;

    if (avformat_open_input(&in_fxt, argv[1], NULL, NULL) < 0)
    {
        printf("can not open the input file context!
");
        goto end;
    }
    if (avformat_find_stream_info(in_fxt, NULL) < 0)
    {
        printf("can not find the stream info!
");
        goto end;
    }

    if(avformat_alloc_output_context2(&out_fxt, NULL, NULL, argv[2]) < 0)
    {
        printf("can not alloc output context!
");
        goto end;
    }

    for (int i = 0; i < in_fxt->nb_streams; i++)
    {
        if (in_fxt->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO)
        {
            //open decoder
            if(0 > avcodec_open2(in_fxt->streams[i]->codec, avcodec_find_decoder(in_fxt->streams[i]->codec->codec_id), NULL))
            {
                printf("can not find or open decoder!
");
                goto end;
            }
            video_index = i;
            //new stream
            out_stream = avformat_new_stream(out_fxt, NULL);
            if (!out_stream)
            {
                printf("can not new stream for output!
");
                goto end;
            }
            //set codec context param
            out_stream->codec->codec = avcodec_find_encoder(/*out_fxt->oformat->video_codec*/AV_CODEC_ID_MKVIDEO);
            out_stream->codec->height = in_fxt->streams[i]->codec->height;
            out_stream->codec->width = in_fxt->streams[i]->codec->width;

            out_stream->codec->time_base = in_fxt->streams[i]->time_base;
            //out_stream->codec->time_base.den = 25;

            out_stream->codec->sample_aspect_ratio = in_fxt->streams[i]->codec->sample_aspect_ratio;
            out_stream->codec->pix_fmt = in_fxt->streams[i]->codec->pix_fmt;

            out_stream->avg_frame_rate.den = out_stream->codec->time_base.num;
            out_stream->avg_frame_rate.num = out_stream->codec->time_base.den;
            if (!out_stream->codec->codec)
            {
                printf("can not find the encoder!
");
                goto end;
            }
            if ((avcodec_open2(out_stream->codec, out_stream->codec->codec, NULL)) < 0)
            {
                printf("can not open the encoder
");
                goto end;
            }
            if (out_fxt->oformat->flags & AVFMT_GLOBALHEADER)
                out_stream->codec->flags |= CODEC_FLAG_GLOBAL_HEADER;
            break;
        }
    }

    if (-1 == video_index)
    {
        printf("found no video stream in input file!
");
        goto end;
    }

    if (!(out_fxt->oformat->flags & AVFMT_NOFILE))
    {
        if(avio_open(&out_fxt->pb, argv[2], AVIO_FLAG_WRITE) < 0)
        {
            printf("can not open output file handle!
");
            goto end;
        }
    }

    if(avformat_write_header(out_fxt, NULL) < 0)
    {
        printf("can not write the header of the output file!
");
        goto end;
    }

    AVPacket pkt_in, pkt_out;
    AVFrame *frame;
    frame = av_frame_alloc();
    av_init_packet(&pkt_in);
    av_init_packet(&pkt_out);
    int got_frame, got_picture;
    int i = 0, frame_index = 0;
    while(1)
    {
        got_frame = -1;
        got_picture = -1;
        if (av_read_frame(in_fxt, &pkt_in) < 0)
        {
            break;
        }
        if (avcodec_decode_video2(in_fxt->streams[video_index]->codec, frame, &got_frame, &pkt_in) < 0)
        {
            printf("can not decoder a frame");
            break;
        }
        av_free_packet(&pkt_in);

        if (got_frame)
        {
            frame->pts = i++;
            pkt_out.data = NULL;//主要这里必须自己初始化，或者必须置为null，不然ff_alloc_packet2函数会报错
            pkt_out.size = 0;
            if (avcodec_encode_video2(out_stream->codec, &pkt_out, frame, &got_picture) < 0)
            {
                printf("can not encode a frame!
");
                break;
            }

            if (got_picture)
            {
                printf("Succeed to encode frame: %5d	size:%5d
",frame_index,pkt_out.size);
                pkt_out.stream_index = out_stream->index;
                frame_index++;
                av_write_frame(out_fxt, &pkt_out);
                av_free_packet(&pkt_out);
            }
        }
    }
    av_frame_free(&frame);

    av_write_trailer(out_fxt);

    //clean
    avcodec_close(out_stream->codec);
    avcodec_close(out_fxt->streams[video_index]->codec);
end:
    avformat_close_input(&in_fxt);

    if (out_fxt && !(out_fxt->oformat->flags & AVFMT_NOFILE))
    {
        avio_close(out_fxt->pb);
    }
    avformat_free_context(out_fxt);
    return 0;
}

3、解释

原理和前面的自定义的muxer、demuxer一样，在这里就不多说了。

from:http://blog.csdn.net/dancing_night/article/details/46360851