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• ffmpeg - wrong length of video

  29 mars 2012, par Victor

  I use ffmpeg to convert a video from mp4 to flv and mpg formats. Just rough conversion with few params :

   ffmpeg -i my_file.mp4 -an -f flv my_new_file.flv

  (I don't need sound so I specified -an)

  When I convert file with 2:23 length I get 0:23 length of flv(or mpg) files. Why does that happen ?

• Django Celery FFMPEG : convert video files

  3 janvier 2012, par sultan

  I'm trying to convert video files using FFMPEG via Celery tasks. The generated command to be executed looks like

  ffmpeg -i /path/to/flv -ar 22050 -ab 96k -r 24 -b 600k -f flv path/to/flv/transcoded/flv_movie.flv

  and when I call the task TranscodeVideoTask.delay(src=filepath, dst=destination_path)
  I get flv_movie.flv file but its size is only about 200Kb and debug output

  Press [q] to stop, [?] for help
  
  [h264 @ 0x10205a200] Reference 3 >= 3
  
  [h264 @ 0x10205a200] error while decoding MB 7 5, bytestream (690)
  
  [h264 @ 0x10205a200] concealing 762 DC, 762 AC, 762 MV errors
  
  frame=   40 fps=  0 q=2.0 Lsize=     136kB time=00:00:01.66 bitrate= 668.2kbits/s dup=0 drop=9    
  
  video:114kB audio:20kB global headers:0kB muxing overhead 1.814991%

  TranscodeVideoTask source

  @task(name="transcode.media")
  
  def TranscodeVideoTask(src, dst):
  
      command = commands.get("flv") % {"src": src, "dst": dst}
  
      os.system(src, dst)
  
      filename = os.path.join(dst, "flv_movie.flv")
  
      YamdiInjector.yamdi(filename, dst)

  When the same command executed manually in the console it works just fine.

  UPDATE
  So far I've composed the following ffmpeg instructions in my bash file and it converts almost every avi file I tested already

  #!/bin/sh
  
  INPUT=$1
  
  OUTPUT=$2/flv_movie.flv
  
  
  
  echo "Input file: ${INPUT}"
  
  echo "Output file: ${OUTPUT}"
  
  echo `ffmpeg -y -i $INPUT -ar 44100 -ab 128k -ac 2 -sameq -f flv $OUTPUT`

  What may cause this strange problem ?

  Sultan

• How to encode video with ffmpeg for playback on Android ?

  3 janvier 2012, par Sean

  I've got a c++ library that is encoding video in realtime from webcams to mp4 files (H264). The settings i've got are as follows :

      codecContex->profile=FF_PROFILE_H264_BASELINE; //Baseline
  
      codecContex->gop_size=250;
  
      codecContex->max_b_frames=0;
  
      codecContex->max_qdiff=4;
  
      codecContex->me_method=libffmpeg::ME_HEX;
  
      codecContex->me_range=16;
  
      codecContex->qmin=10;
  
      codecContex->qmax=51;
  
      codecContex->qcompress=0.6;
  
      codecContex->keyint_min=10;
  
      codecContex->trellis=0;
  
      codecContex->level=13; //Level 1.3
  
      codecContex->weighted_p_pred = 2;
  
      codecContex->flags2|=CODEC_FLAG2_WPRED+CODEC_FLAG2_8X8DCT;

  This creates MP4 files that play on iOS devices and on Windows Phone 7 devices but not on Android devices. I've read that Android only supports movies encoded with the baseline profile. These settings should produce a baseline movie but when I look at the generated MP4 file with MediaInfo it says it's AVC(High@L1.3). This might be why it's not working but I can't seem to get it to generate something with AVC(Baseline@L1.3)...

  If I remove the last line :

  codecContex->flags2|=CODEC_FLAG2_WPRED+CODEC_FLAG2_8X8DCT;

  Then MediaInfo reports the file as being "AVC(Main@L1.3)" instead - but those flags are part of the Baseline profile !