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• Why motion vector extracted from b frames are unchange ?

  19 août 2019, par 霍宇琦

  I am writing c codes to extract motion vectors from b frame in MPEG4(Part2) compressed video format. But some motion vector seems wrong.

  I use a raw video clips, using the extract_mvs.c from ffmpeg 4.2. For example if the frame seq is IPBPPBPP.... i can get all the side data for all frame. But when inspecting the mv->src_x, mv->src_y, mv->dst_x, mv->dst_y i find that all the srcs are equal to dsts for some individual frames, there must be sth wrong in it, but i change little from the official code.

  //modify from ffmpeg/doc/example/extract_mvs.c:
  
  
  
  while(getting frames one by one) {
  
      AVFrameSideData *sd;
  
      video_frame_count++;
  
  
  
      //printf("%d", video_frame_count);
  
      if(video_frame_count < 19){
  
          if (frame->pict_type == AV_PICTURE_TYPE_I ) printf("\nI");
  
          if (frame->pict_type == AV_PICTURE_TYPE_B ) printf("B"); 
  
          if (frame->pict_type == AV_PICTURE_TYPE_P ) printf("P");
  
  
  
          sd = av_frame_get_side_data(frame, AV_FRAME_DATA_MOTION_VECTORS);
  
          if (sd) {
  
              const AVMotionVector *mvs = (const AVMotionVector *)sd->data;
  
              for (i = 0; i < sd->size / sizeof(*mvs); i++) {
  
                  const AVMotionVector *mv = &mvs[i];
  
                  if (mv->dst_x - mv->src_x != 0 || mv->dst_y - mv->src_y != 0) {
  
                  printf("%d,%2d,%2d,%2d,%4d,%4d,%4d,%4d,0x%"PRIx64"\n",
  
                      video_frame_count, mv->source,
  
                      mv->w, mv->h, mv->src_x, mv->src_y,
  
                      mv->dst_x, mv->dst_y, mv->flags);
  
                      break;
  
                  }
  
              }
  
          }
  
          av_frame_unref(frame);
  
      }
  
  }

  Outputs are :

  Input #0, avi, from 'origin.avi':
  
    Duration: 00:00:13.63, start: 0.000000, bitrate: 492 kb/s
  
      Stream #0:0: Video: mpeg4 (DX50 / 0x30355844), yuv420p, 320x240 [SAR 1:1 DAR 4:3], 486 kb/s, 30 fps, 30 tbr, 30 tbn, 30k tbc
  
      Metadata:
  
        title           : H:\HumanActionDB\MotionClips\hmdb51_30fps_wBrd_10off_divx\brush_??
  
  framenum,source,blockw,blockh,srcx,srcy,dstx,dsty,flags
  
  
  
  [mpeg4 @ 0x55739dc29580] Video uses a non-standard and wasteful way to store B-frames ('packed B-frames'). Consider using the mpeg4_unpack_bframes bitstream filter without encoding but stream copy to fix it.
  
  IP2,-1,16,16, 137,  24, 136,  24,0x0
  
  BP4,-1,16,16, 152,  57, 152,  56,0x0
  
  P5,-1,16,16,  56, 155,  56, 152,0x0
  
  BP7,-1,16,16, 151,  40, 152,  40,0x0
  
  PB9,-1,16,16, 151,  40, 152,  40,0x0
  
  P10,-1,16,16, 152,  39, 152,  40,0x0
  
  P11,-1,16,16,  26,  55,  24,  56,0x0
  
  B12,-1,16,16, 152,  39, 152,  40,0x0
  
  P13,-1,16,16, 152,  39, 152,  40,0x0
  
  P14,-1,16,16,  41, 168,  40, 168,0x0
  
  B15,-1,16,16, 152,  39, 152,  40,0x0
  
  P16,-1,16,16, 153,  39, 152,  40,0x0
  
  PB18,-1,16,16, 168,  55, 168,  56,0x0

  you can see that the third frame(B) and the sixth, eighth frame(B, P) and the 17th frame (P) can be read, and the data can be extract from them, but

  mv->dst_x == mv->src_x && mv->dst_y - mv->src_y

  Can someone help me ? Thanks.

• Error trying to stream multiple files - Invalid data found when processing input

  14 avril 2020, par xybrek

  ffmpeg -re -stream_loop -1 -i mylist.txt -f mpegts -vcodec copy -acodec copy http://localhost:8081/yoursecret

  



  mylist.txt file contains :

  



  file 'out001.ts'
file 'out002.ts'


  



  up to out327.ts

  



  Here's the output of the above command :

  



  ffmpeg version git-2020-04-03-52523b6 Copyright (c) 2000-2020 the FFmpeg developers
  built with gcc 9.3.1 (GCC) 20200328
  configuration: --enable-gpl --enable-version3 --enable-sdl2 --enable-fontconfig --enable-gnutls --enable-iconv --enable-libass --enable-libdav1d --enable-libbluray --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libsrt --enable-libtheora --enable-libtwolame --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libzimg --enable-lzma --enable-zlib --enable-gmp --enable-libvidstab --enable-libvmaf --enable-libvorbis --enable-libvo-amrwbenc --enable-libmysofa --enable-libspeex --enable-libxvid --enable-libaom --enable-libmfx --enable-ffnvcodec --enable-cuda-llvm --enable-cuvid --enable-d3d11va --enable-nvenc --enable-nvdec --enable-dxva2 --enable-avisynth --enable-libopenmpt --enable-amf
  libavutil      56. 42.102 / 56. 42.102
  libavcodec     58. 77.101 / 58. 77.101
  libavformat    58. 42.100 / 58. 42.100
  libavdevice    58.  9.103 / 58.  9.103
  libavfilter     7. 77.101 /  7. 77.101
  libswscale      5.  6.101 /  5.  6.101
  libswresample   3.  6.100 /  3.  6.100
  libpostproc    55.  6.100 / 55.  6.100
mylist.txt: Invalid data found when processing input


  



  However streaming individual files works :

  



  ffmpeg -re -stream_loop -1 -i out001.ts -f mpegts -vcodec copy -acodec copy http://localhost:8081/yoursecret


  



  I've also tried but also does not work :

  



  ffmpeg -re -stream_loop -1 -i <(for %%i in (*.ts) do @echo file '%%i') -f mpegts -vcodec copy -acodec copy http://localhost:8081/yoursecret


  


• Can't split 24bit flac files on the command line [closed]

  21 mars 2023, par Martin

  I am trying to export a 24bit flac file in my ubuntu terminal. I've tried two different methods, but neither work.

  


  Method 1 : shntool

  


  when I run this command :
shntool split -f times.cue -O always -o lowq_full_silence.flac

  


  where lowq_full_silence.flac was rendered in audacity as a flac file with level=0 and bit depth=16 bit, my command works.

  


  but if i run this command :

  


  shntool split -f times.cue -O always -o full_hq.flac

  


  where full_hq.flac has level=8 and bit depth=24 bit
The command fails :

  


  shntool [split]: warning: unsupported format 0xfffe (Unknown) while processing file: [full_hq.flac]
shntool [split]: error: cannot continue due to error(s) shown above


  


  https://bugs.launchpad.net/ubuntu/+source/shntool/+bug/2000794

  


  Method 2 : ffmpeg

  


  Trying to split the flac file with comma separated 'split points' input

  


  ffmpeg -i "full_hq.flac" -c copy -map 0 -f segment -segment_times "22,441,556,559" "%d_output.flac"

  


  But the output from this ffmpeg command has broken length metadata :

  


  https://trac.ffmpeg.org/ticket/4905

  


  Is there a better way to split a high quality 24bit flac file into individual segments, where each exported segment file has correct length metadata ?

  


  Files :
https://file.io/lvGTUEgQArb7