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• aacpsy : correct calculation of minath in psy_3gpp_init

  21 avril 2015, par Andreas Cadhalpun

  aacpsy : correct calculation of minath in psy_3gpp_init
  The minimum of the ath(x, ATH_ADD) function depends on ATH_ADD.
  
  This patch uses the first order approximation to determine it.
  For ATH_ADD = 4 this results in the value at 3407.06812 (-5.24241638)
  
  not the one at 3410 (-5.24237967).
  CC : libav-stabl@libav.org
  
  Signed-off-by : Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>
  
  Signed-off-by : Anton Khirnov <anton@khirnov.net>
  

  • [DBH] libavcodec/aacpsy.c

• aacpsy : correct calculation of minath in psy_3gpp_init

  21 avril 2015, par Andreas Cadhalpun

  aacpsy : correct calculation of minath in psy_3gpp_init
  The minimum of the ath(x, ATH_ADD) function depends on ATH_ADD.
  
  This patch uses the first order approximation to determine it.
  For ATH_ADD = 4 this results in the value at 3407.06812 (-5.24241638)
  
  not the one at 3410 (-5.24237967).
  Signed-off-by : Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>
  
  Approved-by : Claudio Freire <klaussfreire@gmail.com>
  
  Signed-off-by : Michael Niedermayer <michaelni@gmx.at>
  

  • [DH] libavcodec/aacpsy.c

• FFmpeg C Api - Reduce fps but maintain video duration

  25 mars 2015, par Justin Bradley

  Using the FFmpeg C API I’m trying to convert an input video into a video that looks like an animated gif - meaning no audio stream and a video stream of 4/fps.

  I have the decode/encode part working. I can drop the audio stream from the output file, but I’m having trouble reducing the fps. I can change the output video stream’s time_base to 4/fps, but it increases the video’s duration - basically playing it in slow mo.

  I think I need to drop the extra frames before I write them to the output container.

  Below is the loop where I read the input frames, and then write them to output container.

  Is this where I’d drop the extra frames ? How do I determine which frames to drop (I,P,B frames) ?

  while(av_read_frame(input_container, &decoded_packet)>=0) {
  
  
  
      if (decoded_packet.stream_index == video_stream_index) {
  
          len = avcodec_decode_video2(input_stream->codec, decoded_frame, &got_frame, &decoded_packet);
  
          if(len < 0) {
  
              exit(1);
  
          }
  
  
  
          if(got_frame) {
  
              av_init_packet(&encoded_packet);
  
              encoded_packet.data =  NULL;
  
              encoded_packet.size =  0;
  
  
  
              if(avcodec_encode_video2(output_stream->codec, &encoded_packet, decoded_frame, &got_frame) < 0) {
  
                  exit(1);
  
              }
  
              if(got_frame) {
  
                  if (output_stream->codec->coded_frame->key_frame) {
  
                      encoded_packet.flags |= AV_PKT_FLAG_KEY;
  
                  }
  
  
  
                  encoded_packet.stream_index = output_stream->index;
  
                  encoded_packet.pts = av_rescale_q(current_frame_num, output_stream->codec->time_base, output_stream->time_base);
  
                  encoded_packet.dts = av_rescale_q(current_frame_num, output_stream->codec->time_base, output_stream->time_base);
  
  
  
                  if(av_interleaved_write_frame(output_container, &encoded_packet) < 0) {
  
                      exit(1);
  
                  }
  
                  else {
  
                      current_frame_num +=1;
  
                  }
  
              }
  
              frame_count+=1;
  
              av_free_packet(&encoded_packet);
  
          }
  
      }
  
  }