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• FFmpeg input file type detection

  17 août 2021, par andbi

  I'm using FFmpeg for converting audio files, and I see that it can automatically derive the correct input source's type regardless of the file's extension and without providing any input type/codec information. At least it works for mp3 and wav files.

  


  The question is which audio file types it might fail to recognize or when it's better to state the input format explicitly (of course, excluding the PCM* types).

  


• ffmpeg errors in the daemon

  3 octobre 2020, par smoto_shei

  I created a shell script to compress a video using ffmpeg(4.3.1).

  


  ffmpeg -y -i \
 '/var/www/System/Backend/Outputs/TempSaveMovie/200703_4_short_5fr_p2(100_20)_r(50_20).mp4' \
 -vcodec h264 -an \
 '/var/www/System/Backend/Outputs/MovieOutputs/200703_4_short_5fr_p2(100_20)_r(50_20).mp4'



  


  If you run this code from the console, it will run without problems.
In fact, we're using the python subscript.call() to execute it. It works fine too.

  


  cmd = 'sh /var/www/System/Backend/cv2toffmpeg.sh'
subprocess.call(cmd, shell=True)


  


  Secondly, if I run it from a daemonized python program, I'll get an error. I get the following error.
You'll get an error like this

  


  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from './Outputs/TempSaveMovie/200703_4_short_5fr_p2(100_20)_r(50_20).mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2mp41
    encoder         : Lavf58.35.100
  Duration: 00:00:06.15, start: 0.000000, bitrate: 10246 kb/s
    Stream #0:0(und): Video: mpeg4 (Simple Profile) (mp4v / 0x7634706D), yuv420p, 1280x720 [SAR 1:1 DAR 16:9], 10244 kb/s, 13 fps, 13 tbr, 13312 tbn, 13 tbc (default)
    Metadata:
      handler_name    : VideoHandler
Stream mapping:
  Stream #0:0 -> #0:0 (mpeg4 (native) -> h264 (h264_nvenc))
Press [q] to stop, [?] for help
[mpeg4 @ 0x55cec17c5480] header damaged
[mpeg4 @ 0x55cec17c6840] header damaged
[mpeg4 @ 0x55cec1855f80] header damaged
[mpeg4 @ 0x55cec1866e00] header damaged
Output #0, mp4, to './Outputs/MovieOutputs/200703_4_short_5fr_p2(100_20)_r(50_20).mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2mp41
    encoder         : Lavf58.45.100
    Stream #0:0(und): Video: h264 (h264_nvenc) (Main) (avc1 / 0x31637661), yuv420p, 1280x720 [SAR 1:1 DAR 16:9], q=-1--1, 2000 kb/s, 13 fps, 13312 tbn, 13 tbc (default)
    Metadata:
      handler_name    : VideoHandler
      encoder         : Lavc58.91.100 h264_nvenc
    Side data:
      cpb: bitrate max/min/avg: 0/0/2000000 buffer size: 4000000 vbv_delay: N/A
Error while decoding stream #0:0: Invalid data found when processing input
[mpeg4 @ 0x55cec17c8780] header damaged
Error while decoding stream #0:0: Invalid data found when processing input
[mpeg4 @ 0x55cec17c5480] header damaged


  


  I think the problem is when you run it from a daemonized process. There seems to be a similar problem in the past.
Ffmpeg does not properly convert videos when run as daemon
I would like to ask for your help to solve this problem. Thank you for your help from Japan.

  


• Capture ffmpeg's metadata output in powershell

  17 janvier 2021, par xdhmoore

  I'm trying to capture the output of ffmpeg in PowerShell(tm) to get some metadata on some ogg & mp3 files. But when I do :

  



  ffmpeg -i file.ogg 2>&1 | sls GENRE


  



  The output includes a bunch of lines without my matching string, "GENRE" :

  



        album_artist    : Post Human Era
      ARTIST          : Post Human Era
      COMMENT         : Visit http://posthumanera.bandcamp.com
      DATE            : 2013
      GENRE           : Music
      TITLE           : Supplies
      track           : 1
At least one output file must be specified


  



  I am guessing something is different in the encoding. ffmpeg's output is colored, so maybe there are color control characters in the output that are breaking things ? Or, maybe ffmpeg's output isn't playing nicely with powershell's default UTF-16 ? I can't figure out if there is another way to redirect stderr and remove the color characters or change the encoding of stderr.

  



  EDIT :
Strangely, I also get indeterminate output. Sometimes the output is as shown above. Sometimes with precisely the same command the output is :

  



        GENRE           :


  



  

  



  Which makes slightly more sense, but is still missing the part of the line I care about ('Music').

  



  Somewhere powershell is interpreting something as newlines that is not newlines.