FFmpeg4入门24：音视频mp3和h264混合（muxer）编码为mp4

上一篇：FFmpeg4入门23：音视频解混合（demuxer）为PCM和YUV420P

解混合的基本操作介绍完了，接下来我们来看一下混合的操作。

先看一下流程图

flow

然后看一下函数调用图

functions

首先打开输入软件，查找两条流

//打开输入视频文件
ret = avformat_open_input(&ifmtCtxVideo, inFilenameVideo, 0, 0);
if (ret < 0)
{
    printf("can't open input video file\n");
    goto end;
}

//查找输入流
ret = avformat_find_stream_info(ifmtCtxVideo, 0);
if (ret < 0)
{
    printf("failed to retrieve input video stream information\n");
    goto end;
}

//打开输入音频文件
ret = avformat_open_input(&ifmtCtxAudio, inFilenameAudio, 0, 0);
if (ret < 0)
{
    printf("can't open input audio file\n");
    goto end;
}

//查找输入流
ret = avformat_find_stream_info(ifmtCtxAudio, 0);
if (ret < 0)
{
    printf("failed to retrieve input audio stream information\n");
    goto end;
}

分配输出的上下文

//新建输出上下文
avformat_alloc_output_context2(&ofmtCtx, NULL, NULL, outFilename);
if (!ofmtCtx)
{
    printf("can't create output context\n");
    goto end;
}

将现有的流数据复制给输出的两条流

//视频输入流
for (i = 0; i < ifmtCtxVideo->nb_streams; ++i)
{
    if (ifmtCtxVideo->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO)
    {
        AVStream *inStream = ifmtCtxVideo->streams[i];
        AVStream *outStream = avformat_new_stream(ofmtCtx, NULL);
        inVideoIndex = i;

        if (!outStream)
        {
            printf("failed to allocate output stream\n");
            goto end;
        }

        outVideoIndex = outStream->index;

        if (avcodec_parameters_copy(outStream->codecpar, inStream->codecpar) < 0)
        {
            printf("faild to copy context from input to output stream");
            goto end;
        }

        outStream->codecpar->codec_tag = 0;

        break;
    }
}

//音频输入流
for (i = 0; i < ifmtCtxAudio->nb_streams; ++i)
{
    if (ifmtCtxAudio->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_AUDIO)
    {
        AVStream *inStream = ifmtCtxAudio->streams[i];
        AVStream *outStream = avformat_new_stream(ofmtCtx, NULL);
        inAudioIndex = i;

        if (!outStream)
        {
            printf("failed to allocate output stream\n");
            goto end;
        }

        outAudioIndex = outStream->index;

        if (avcodec_parameters_copy(outStream->codecpar, inStream->codecpar) < 0)
        {
            printf("faild to copy context from input to output stream");
            goto end;
        }

        outStream->codecpar->codec_tag = 0;

        break;
    }
}

最为关键的转换的步骤

AVFormatContext *ifmtCtx = NULL;
AVStream *inStream, *outStream;
int streamIndex = 0;

if (av_compare_ts(curPstVideo, ifmtCtxVideo->streams[inVideoIndex]->time_base, curPstAudio, ifmtCtxAudio->streams[inAudioIndex]->time_base) < 0)
{
    ifmtCtx = ifmtCtxVideo;
    streamIndex = outVideoIndex;

    if (av_read_frame(ifmtCtx, &packet) >= 0)
    {
        do
        {
            inStream = ifmtCtx->streams[packet.stream_index];
            outStream = ofmtCtx->streams[streamIndex];

            if (packet.stream_index == inVideoIndex)
            {
                //Fix: No PTS(Example: Raw H.264
                //Simple Write PTS
                if (packet.pts == AV_NOPTS_VALUE)
                {
                    //write PTS
                    AVRational timeBase1 = inStream->time_base;
                    //Duration between 2 frames
                    int64_t calcDuration = (double)AV_TIME_BASE/av_q2d(inStream->r_frame_rate);
                    //Parameters
                    packet.pts = (double)(frameIndex*calcDuration)/(double)(av_q2d(timeBase1)*AV_TIME_BASE);
                    packet.dts = packet.pts;
                    packet.duration = (double)calcDuration/(double)(av_q2d(timeBase1)*AV_TIME_BASE);
                    frameIndex++;
                }

                curPstVideo = packet.pts;
                break;
            }
        }while(av_read_frame(ifmtCtx, &packet) >= 0);
    }
    else
    {
        break;
    }
}else{
    ifmtCtx = ifmtCtxAudio;
    streamIndex = outAudioIndex;

    if (av_read_frame(ifmtCtx, &packet) >= 0)
    {
        do
        {
            inStream = ifmtCtx->streams[packet.stream_index];
            outStream = ofmtCtx->streams[streamIndex];

            if (packet.stream_index == inAudioIndex)
            {
                //Fix: No PTS(Example: Raw H.264
                //Simple Write PTS
                if (packet.pts == AV_NOPTS_VALUE)
                {
                    //write PTS
                    AVRational timeBase1 = inStream->time_base;
                    //Duration between 2 frames
                    int64_t calcDuration = (double)AV_TIME_BASE/av_q2d(inStream->r_frame_rate);
                    //Parameters
                    packet.pts = (double)(frameIndex*calcDuration)/(double)(av_q2d(timeBase1)*AV_TIME_BASE);
                    packet.dts = packet.pts;
                    packet.duration = (double)calcDuration/(double)(av_q2d(timeBase1)*AV_TIME_BASE);
                    frameIndex++;
                }

                curPstAudio = packet.pts;
                break;
            }
        }while(av_read_frame(ifmtCtx, &packet) >= 0);
    }
    else
    {
        break;
    }
}

//FIX:Bitstream Filter
#if USE_H264BSF
    av_bitstream_filter_filter(h264bsfc, inStream->codec, NULL, &packet.data, &packet.size, packet.data, packet.size, 0);
#endif
#if USE_AACBSF
    av_bitstream_filter_filter(aacbsfc, outStream->codec, NULL, &packet.data, &packet.size, packet.data, packet.size, 0);
#endif

//Convert PTS/DTS
packet.pts = av_rescale_q_rnd(packet.pts, inStream->time_base, outStream->time_base, (AVRounding)(AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX));
packet.dts = av_rescale_q_rnd(packet.dts, inStream->time_base, outStream->time_base, (AVRounding)(AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX));
packet.duration = av_rescale_q(packet.duration, inStream->time_base, outStream->time_base);
packet.pos = -1;
packet.stream_index = streamIndex;

//write
if (av_interleaved_write_frame(ofmtCtx, &packet) < 0)
{
    printf("error muxing packet");
    break;
}

av_packet_unref(&packet);