8
votes

i have this ffmpeg command

ffmpeg -i c:\input.mp4 -vcodec copy -acodec copy -vbsf h264_mp4toannexb c:\output.ts.

The above command successfully converts input.mp4 to output.ts.

I need to implement the same functionality via code (using the ffmpeg library).

Does anybody know how to copy from one container to another without decoding and encoding?

1
Thanks for asking this :)Bhumit Mehta

1 Answers

17
votes

If you are looking just for stream copy you can do this quite easily. You can refer following steps.

//1. Do initialization using 

    av_register_all();

// 2. Open input file using  

    avformat_open_input( &m_informat, filename.c_str(), 0, 0));

//3. Find input stream info.

     if ((ret = avformat_find_stream_info(m_informat, 0))< 0)
        {
           av_strerror(ret,errbuf,sizeof(errbuf));
           PRINT_VAL("Not Able to find stream info:: ", errbuf)
           ret = -1;
           return ret;
        }

        for (unsigned int i = 0; i<m_informat->nb_streams; i++)
        {
           if(m_informat->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO)
           {
              PRINT_MSG("Found Video Stream ")
              m_in_vid_strm_idx = i;
              m_in_vid_strm = m_informat->streams[i];
           }

        if(m_informat->streams[i]->codec->codec_type == AVMEDIA_TYPE_AUDIO)
        {
            m_in_aud_strm_idx = i;
            m_in_aud_strm = m_informat->streams[i];
         }


// 4. Create ouputfile  and allocate output format.

   AVOutputFormat *outfmt = NULL;
   std::string outfile = std::string(filename) + "clip_out.ts";
        outfmt = av_guess_format(NULL,outfile.c_str(),NULL);
     if(outfmt == NULL)
        {
            ret = -1;
            return ret;
        }
        else
        {
            m_outformat = avformat_alloc_context();
            if(m_outformat)
            {
                m_outformat->oformat = outfmt;
                _snprintf(m_outformat->filename, 
                 sizeof(m_outformat->filename), "%s", outfile.c_str());    
            }
            else
            {
                ret = -1;
                return ret;
            }
        }

//5. Add audio and video stream to output format.

        AVCodec *out_vid_codec,*out_aud_codec;
        out_vid_codec = out_aud_codec = NULL;

        if(outfmt->video_codec != AV_CODEC_ID_NONE && m_in_vid_strm != NULL)
        {
            out_vid_codec = avcodec_find_encoder(outfmt->video_codec);
            if(NULL == out_vid_codec)
            {
                PRINT_MSG("Could Not Find Vid Encoder")
                ret = -1;
                return ret;
            }
            else
            {
                PRINT_MSG("Found Out Vid Encoder ")
                m_out_vid_strm = avformat_new_stream(m_outformat, out_vid_codec);
                if(NULL == m_out_vid_strm)
                {
                     PRINT_MSG("Failed to Allocate Output Vid Strm ")
                     ret = -1;
                     return ret;
                }
                else
                {
                     PRINT_MSG("Allocated Video Stream ")
                     if(avcodec_copy_context(m_out_vid_strm->codec, 
                        m_informat->streams[m_in_vid_strm_idx]->codec) != 0)
                     {
                        PRINT_MSG("Failed to Copy Context ")
                        ret = -1;
                        return ret;
                     }
                     else
                     {
                        m_out_vid_strm->sample_aspect_ratio.den = 
                        m_out_vid_strm->codec->sample_aspect_ratio.den;

                        m_out_vid_strm->sample_aspect_ratio.num = 
                        m_in_vid_strm->codec->sample_aspect_ratio.num;
                        PRINT_MSG("Copied Context ")
                        m_out_vid_strm->codec->codec_id = m_in_vid_strm->codec->codec_id;
                        m_out_vid_strm->codec->time_base.num = 1;
                        m_out_vid_strm->codec->time_base.den = 
                        m_fps*(m_in_vid_strm->codec->ticks_per_frame);         
                        m_out_vid_strm->time_base.num = 1;
                        m_out_vid_strm->time_base.den = 1000;
                        m_out_vid_strm->r_frame_rate.num = m_fps;
                        m_out_vid_strm->r_frame_rate.den = 1;
                        m_out_vid_strm->avg_frame_rate.den = 1;
                        m_out_vid_strm->avg_frame_rate.num = m_fps;
                        m_out_vid_strm->duration = (m_out_end_time - m_out_start_time)*1000;
                     }
                   }
                }
          }

        if(outfmt->audio_codec != AV_CODEC_ID_NONE && m_in_aud_strm != NULL)
        {
            out_aud_codec = avcodec_find_encoder(outfmt->audio_codec);
            if(NULL == out_aud_codec)
            {
                PRINT_MSG("Could Not Find Out Aud Encoder ")
                ret = -1;
                return ret;
            }
            else
            {
                PRINT_MSG("Found Out Aud Encoder ")
                m_out_aud_strm = avformat_new_stream(m_outformat, out_aud_codec);
                if(NULL == m_out_aud_strm)
                {
                    PRINT_MSG("Failed to Allocate Out Vid Strm ")
                    ret = -1;
                    return ret;
                }
                else
                {
                    if(avcodec_copy_context(m_out_aud_strm->codec, 
                       m_informat->streams[m_in_aud_strm_idx]->codec) != 0)
                    {
                        PRINT_MSG("Failed to Copy Context ")
                        ret = -1;
                        return ret;
                    }
                    else
                     {
                        PRINT_MSG("Copied Context ")
                        m_out_aud_strm->codec->codec_id = m_in_aud_strm->codec->codec_id;
                        m_out_aud_strm->codec->codec_tag = 0;
                        m_out_aud_strm->pts = m_in_aud_strm->pts;
                        m_out_aud_strm->duration = m_in_aud_strm->duration;
                        m_out_aud_strm->time_base.num = m_in_aud_strm->time_base.num;
                        m_out_aud_strm->time_base.den = m_in_aud_strm->time_base.den;

                    }
                }
             }
          }
 // 6. Finally output header.
      if (!(outfmt->flags & AVFMT_NOFILE)) 
          {
            if (avio_open2(&m_outformat->pb, outfile.c_str(), AVIO_FLAG_WRITE,NULL, NULL) < 0) 
            {
                    PRINT_VAL("Could Not Open File ", outfile)
                    ret = -1;
                    return ret;
            }
          }
            /* Write the stream header, if any. */
          if (avformat_write_header(m_outformat, NULL) < 0) 
          {
                PRINT_VAL("Error Occurred While Writing Header ", outfile)
                ret = -1;
                return ret;
          }
          else
          {
                PRINT_MSG("Written Output header ")
                m_init_done = true;
          }

// 7. Now in while loop read frame using av_read_frame and write to output format using 
//  av_interleaved_write_frame(). You can use following loop

      while(av_read_frame(m_informat, &pkt) >= 0 && (m_num_frames-- > 0))
            {
                if(pkt.stream_index == m_in_vid_strm_idx)
                {
                    PRINT_VAL("ACTUAL VID Pkt PTS ",av_rescale_q(pkt.pts,m_in_vid_strm->time_base, m_in_vid_strm->codec->time_base))
                    PRINT_VAL("ACTUAL VID Pkt DTS ", av_rescale_q(pkt.dts, m_in_vid_strm->time_base, m_in_vid_strm->codec->time_base ))
                    av_init_packet(&outpkt);
                    if(pkt.pts != AV_NOPTS_VALUE)
                    {
                        if(last_vid_pts == vid_pts)
                        {
                            vid_pts++;
                            last_vid_pts = vid_pts;
                        }
                        outpkt.pts = vid_pts;   
                        PRINT_VAL("ReScaled VID Pts ", outpkt.pts)
                    }
                    else
                    {
                        outpkt.pts = AV_NOPTS_VALUE;
                    }

                    if(pkt.dts == AV_NOPTS_VALUE)
                    {
                        outpkt.dts = AV_NOPTS_VALUE;
                    }
                    else
                    {
                        outpkt.dts = vid_pts;
                        PRINT_VAL("ReScaled VID Dts ", outpkt.dts)
                        PRINT_MSG("=======================================")
                    }

                    outpkt.data = pkt.data;
                    outpkt.size = pkt.size;
                    outpkt.stream_index = pkt.stream_index;
                    outpkt.flags |= AV_PKT_FLAG_KEY;
                    last_vid_pts = vid_pts;
                    if(av_interleaved_write_frame(m_outformat, &outpkt) < 0)
                    {
                        PRINT_MSG("Failed Video Write ")
                    }
                    else
                    {
                        m_out_vid_strm->codec->frame_number++;
                    }
                    av_free_packet(&outpkt);
                    av_free_packet(&pkt);
                }
                else if(pkt.stream_index == m_in_aud_strm_idx)
                {
                    PRINT_VAL("ACTUAL AUD Pkt PTS ", av_rescale_q(pkt.pts, m_in_aud_strm->time_base, m_in_aud_strm->codec->time_base))
                    PRINT_VAL("ACTUAL AUD Pkt DTS ", av_rescale_q(pkt.dts, m_in_aud_strm->time_base, m_in_aud_strm->codec->time_base))
                    //num_aud_pkt++;
                    av_init_packet(&outpkt);
                    if(pkt.pts != AV_NOPTS_VALUE)
                    {
                        outpkt.pts = aud_pts;
                        PRINT_VAL("ReScaled AUD PTS ", outpkt.pts)
                    }
                    else
                    {
                        outpkt.pts = AV_NOPTS_VALUE;
                    }

                    if(pkt.dts == AV_NOPTS_VALUE)
                    {
                        outpkt.dts = AV_NOPTS_VALUE;
                    }
                    else
                    {
                        outpkt.dts = aud_pts;
                        PRINT_VAL("ReScaled AUD DTS ", outpkt.dts)
                        PRINT_MSG("====================================")
                        if( outpkt.pts >= outpkt.dts)
                        {
                            outpkt.dts = outpkt.pts;
                        }
                        if(outpkt.dts == aud_dts)
                        {
                            outpkt.dts++;
                        }
                        if(outpkt.pts < outpkt.dts)
                        {
                            outpkt.pts = outpkt.dts;
                            aud_pts = outpkt.pts;
                        }
                    }

                    outpkt.data = pkt.data;
                    outpkt.size = pkt.size;
                    outpkt.stream_index = pkt.stream_index;
                    outpkt.flags |= AV_PKT_FLAG_KEY;
                    vid_pts = aud_pts;
                    aud_pts++;
                    if(av_interleaved_write_frame(m_outformat, &outpkt) < 0)
                    {
                        PRINT_MSG("Faile Audio Write ")
                    }
                    else
                    {
                        m_out_aud_strm->codec->frame_number++;
                    }
                    av_free_packet(&outpkt);
                    av_free_packet(&pkt);
            }
            else
            {
                PRINT_MSG("Got Unknown Pkt ")
                //num_unkwn_pkt++;
            }
            //num_total_pkt++;
        }

//8. Finally write trailer and clean up everything

     av_write_trailer(m_outformat);
        av_free_packet(&outpkt);
        av_free_packet(&pkt);