ffmpeg如何从内存读取h264音视频流进行解码显示

来源：互联网发布：开票软件被收藏编辑：程序博客网时间：2024/05/22 17:31

由于项目组重组，自己有幸开始做音视频编解码方面的研发工作，现将自己近期的工作收获作为BOLG的方式记录起来，方便自己日后查阅和学习。说到H264编解码，不能不提到ffmpeg，据自己查证的资料显示，现大部分软件的H264编解码基本都是使用ffmpeg作为自己的三方库工具，关于ffmpeg有多牛，这里不作赘述。

按照之前查阅的资料，ffmpeg可以解码rtp网络流、从内存读取数据流来解码、读取文件流并解码，本篇幅主要介绍ffmpeg如何从内存读取h264数据流并解码显示，这里只重点关注成功解码h264视频流的关键步骤，关于视频显示与音视叔同步部分将在后续内容继续更新！

先帖上部分代码:

CDecoder::CDecoder():m_avFmtContext( NULL ),m_pFrame( NULL ),m_pCodecCtx( NULL ),m_bQuit( false ),m_openTd( NULL ),m_disPlayTd( NULL ),m_direcDraw( NULL ){    av_register_all();}CDecoder::~CDecoder(){}bool CDecoder::init( void *hwnd ){    if ( m_avFmtContext )    {        avformat_close_input( &m_avFmtContext );        m_avFmtContext = NULL;    }    if ( !m_avFmtContext )    {        m_avFmtContext = avformat_alloc_context();        AVCodec* pCodec = avcodec_find_decoder( AV_CODEC_ID_H264 );        if ( pCodec )        {            av_format_set_video_codec( m_avFmtContext, pCodec );            m_avFmtContext->video_codec_id = AV_CODEC_ID_H264;//AV_CODEC_ID_H264;        }    }    if ( !m_direcDraw )    {        m_direcDraw = new CDirectDraw((HWND)hwnd );        m_direcDraw->dirrectDrawInit((HWND)hwnd);    }    m_bQuit = false;    if ( !m_spOpenThread )    {        m_spOpenThread.reset( new boost::thread( boost::bind( &CDecoder::openStream, this ) ) );    }

    return true;}void CDecoder::openStream(){    uint8_t* pBuf = (uint8_t *)av_mallocz( sizeof(uint8_t) * BUF_SIZE );    m_avFmtContext->pb = avio_alloc_context( pBuf, BUF_SIZE, 0, this, readRawDataCB, NULL, NULL );    if ( !m_avFmtContext->pb )    {        std::cout << "avio_alloc_context error!" << std::endl;        return;    }    // [ 探测流信息，主要来填充AVInputFormat结构体，为下面的打开流IO作准备 ]    AVInputFormat *pAvInputFmt = NULL;    //AVInputFormat *pAvInputFmt = av_find_input_format("h264");    if ( av_probe_input_buffer( m_avFmtContext->pb, &pAvInputFmt, NULL, NULL, 0, 0 ) < 0 )    {        std::cout << __FUNCTION__ << " : " << __LINE__ << " error! " << std::endl;        //avio_close( m_avFmtContext->pb );        //av_err2str        m_avFmtContext->pb = NULL;        return;    }    av_init_packet(&m_avpkt);    if ( !m_pFrame )    {        m_pFrame = av_frame_alloc();    }        AVFrame *pFrameRGB = NULL;    // [ 打开流 ]    if ( avformat_open_input( &m_avFmtContext, NULL, pAvInputFmt, NULL ) < 0 )    {        std::cout << "avformat_open_input error!" << std::endl;        return;    }    //读取数据    int frameFinished = -1;    int videoStreamNum = -1;    AVCodecContext *pCodecCtx = NULL;    AVCodec *pCodec = NULL;    static struct SwsContext *img_convert_ctx = NULL;    while( true )    {        if ( m_bQuit )            return;        int ret = av_read_frame(m_avFmtContext, &m_avpkt);        if ( ret < 0 )        {            boost::thread::sleep( boost::get_system_time() + boost::posix_time::milliseconds( 10) );            continue;        }        if ( videoStreamNum == -1 )        {            // [ 查找是否有视频流 ]            for(int i=0; i<(m_avFmtContext->nb_streams); i++)            {                if(m_avFmtContext->streams[i]->codec->codec_type==AVMEDIA_TYPE_VIDEO) //找出视频流                {                    videoStreamNum=i;                    break;                }            }            if(videoStreamNum==-1)                return;            // [ 找出解码器信息上下文和AVCodec解码器，用于下面打开解码器和解码AvPacket ]            pCodecCtx = m_avFmtContext->streams[videoStreamNum]->codec;            // 从视频流中找出相应解码器            pCodec=avcodec_find_decoder(m_avFmtContext->streams[videoStreamNum]->codec->codec_id);            if(pCodec==NULL)             {                fprintf(stderr, "Unsupported codec!\n");                return;            }            // [ 打开流信息中查找到流解码器 ]            if(avcodec_open2(pCodecCtx, pCodec,NULL)<0)                return; // Could not open codec            pCodecCtx->width = 1920;            pCodecCtx->height = 1080;            pCodecCtx->pix_fmt = AV_PIX_FMT_YUV420P;            if ( !pFrameRGB )            {                pFrameRGB = av_frame_alloc();                if ( !pFrameRGB )                    return;                pFrameRGB->width  = pCodecCtx->width;                pFrameRGB->height = pCodecCtx->height;                pFrameRGB->format = PIX_FMT_YUV420P;                if ( av_image_alloc( pFrameRGB->data, pFrameRGB->linesize,                     pCodecCtx->width, pCodecCtx->height, PIX_FMT_YUV420P, 1 ) < 0 )                {                     av_frame_free( &pFrameRGB );                    pFrameRGB = NULL;                    return;                }            }            img_convert_ctx = sws_getContext(pCodecCtx->width, pCodecCtx->height,                pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height,                PIX_FMT_YUV420P, SWS_BICUBIC, NULL, NULL, NULL);        }        if(m_avpkt.stream_index==videoStreamNum)         {            // 解码            avcodec_decode_video2( pCodecCtx, m_pFrame, &frameFinished, &m_avpkt );            if ( frameFinished > 0 )             {                static uint8_t *p = NULL;                 p = m_pFrame->data[1];                m_pFrame->data[1] = m_pFrame->data[2];                m_pFrame->data[2] = p;                sws_scale(img_convert_ctx, m_pFrame->data, m_pFrame->linesize,                    0, pCodecCtx->height,pFrameRGB->data,pFrameRGB->linesize);                sPictureSize sPicSize;                sPicSize.nHeight = pCodecCtx->height;                sPicSize.nWidth  = pCodecCtx->width;                m_direcDraw->dirrectDrawInputData(pFrameRGB->data[0], sPicSize);                m_direcDraw->directDrawUpDateData();                //SaveAsBMP( pFrameRGB, pCodecCtx->width, pCodecCtx->height, 1, 1 );            }        }        av_free_packet(&m_avpkt);    }}

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