[libav-user] Decoding FLV Movie

[Thomas Roland ESI]

Hi, 

I have to transcode a short FLV movie (570k; 480*360; without audio) to
MJPEG but I didn’t find any tutorials to do that :s

My problem is for the decoding of the FLV movie. 

It’s the first time I use ffmpeg to decode :s 

(Libavcodec Version 51.7.0)

Could you check the code below please, from the next following few remarks ?

-   Did I initialize the codec correctly ?

-   Is the AvCodecContext filled correctly for FLV ?

-    avcodec_find_decoder(CODEC_ID_FLV1)returns a good value but
avcodec_decode_video() returns -1

-    if I replace CODEC_ID_FLV1 by CODEC_ID_H263 (because FLV = Sorenson
H263), avcodec_decode_video returns a good value but got_picture = 0

-    Is PIX_FMT_YUVJ420P the good PixelFormat ?

 

Sorry for my “french” english.

Thank you in advance.

 

The following code is a sample of the complete code but should be
sufficient.

 

avcodec_init();

av_register_all();

 

m_pCodecCtx = avcodec_alloc_context();

avcodec_get_context_defaults(m_pCodecCtx);

 

m_pCodecCtx->width=m_iWidth;    // Width of the input FLV video: 480

m_pCodecCtx->height=m_iHeight;  // Heigth of the input FLV video: 360

 

// RGB24 Context Init

m_pRGB24CodecCtx = avcodec_alloc_context();

m_pRGB24CodecCtx->width=m_iWidth;

m_pRGB24CodecCtx->height=m_iHeight;

m_pRGB24CodecCtx->pix_fmt = (PixelFormat)PIX_FMT_BGR24;

m_pRGB24Frame = avcodec_alloc_frame();   

 

switch(m_iCodecID)

{     

      case CODEC_ID_FLV1 :                           

            m_pCodec = avcodec_find_decoder(CODEC_ID_FLV1);
//CODEC_ID_H263);

            if (!m_pCodec)

            {

                  return false; // !!! !!! !!!

            }


                  

            m_pCodecCtx->thread_count      = 1;

            m_pCodecCtx->workaround_bugs   = FF_BUG_AUTODETECT;

            m_pCodecCtx->error_resilience  = FF_ER_COMPLIANT;

            m_pCodecCtx->error_concealment = 3; 

            m_pCodecCtx->idct_algo         = FF_IDCT_AUTO;

            m_pCodecCtx->debug             = 0;

            m_pCodecCtx->debug_mv          = 0;                  

                  

            //m_pCodecCtx->codec_tag         = 2;                

 

            // Inform the codec that we can handle truncated bitstreams --
i.e.,

            // bitstreams where frame boundaries can fall in the middle of
packets

            if(m_pCodec->capabilities & CODEC_CAP_TRUNCATED)

                  m_pCodecCtx->flags|=CODEC_FLAG_TRUNCATED;


 

            if (avcodec_open(m_pCodecCtx, m_pCodec) < 0)

            {

                  return false; // !!! !!! !!!

            }

            m_pCodecCtx->pix_fmt = (PixelFormat) PIX_FMT_YUVJ420P; // or
PIX_FMT_RGB24 ?

            break;

 

      default:                

            CString sMsg;

            sMsg.Format(_T("[CVideoCodec::%d] ERROR not
implemented"),int(this));

            m_pSession->WriteLog(sMsg,1);

            break;

 

      }

 

      m_iPixFmt = m_pCodecCtx->pix_fmt;

 

      } else

      {

            m_pCodecCtx->pix_fmt = (PixelFormat) m_iPixFmt;

      }     

 

      m_pInputFrame = avcodec_alloc_frame();

      int numBytes=avpicture_get_size(m_iPixFmt, m_pCodecCtx->width,
m_pCodecCtx->height);

      m_buffer=new unsigned char[numBytes];

      avpicture_fill((AVPicture *)m_pInputFrame, m_buffer, m_iPixFmt,
m_pCodecCtx->width, m_pCodecCtx->height);   

 

      m_pOutputFrame= avcodec_alloc_frame();

}

 

int got_picture = 0;

int iDecodedBytesCount = 0;                    

                  

iDecodedBytesCount = avcodec_decode_video ( m_pCodecCtx,

                        m_pInputFrame,

                        //m_pOutputFrame,

                        &got_picture,

                        Buffer,                      

                        uiBufferUsed );

 

 

 

 

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