Recherche avancée

Sur d’autres sites (4046)

• ffmpeg can't transcode DVD ac3 audio stream, but VLC can play it

  21 février 2020, par RalphORama

  I’m attempting to transcode a DVD to a single MKV file. I’ve had success in the past with other DVDs, but I’m running into an error I haven’t seen before.

  First I concatenate the VOB files I want to transcode :

  cat VTS_02_1.VOB VTS_02_2.VOB VTS_02_3.VOB > WMAV.VOB

  ffprobe output :

  $ ffprobe -analyzeduration 100M -probesize 100M WMAV.VOB                                                                         Input #0, mpeg, from 'WMAV.VOB':
  
    Duration: 01:05:19.42, start: 0.300300, bitrate: 5686 kb/s
  
      Stream #0:0[0x1bf]: Data: dvd_nav_packet
  
      Stream #0:1[0x1e0]: Video: mpeg2video (Main), yuv420p(tv, smpte170m, top first), 720x480 [SAR 32:27 DAR 16:9], 29.97 fps, 29.97 tbr, 90k tbn, 59.94 tbc
  
      Stream #0:2[0x80]: Audio: ac3, 48000 Hz, stereo, fltp, 192 kb/s
  
  Unsupported codec with id 100357 for input stream 0

  Then I run this command to transcode the file :

  ffmpeg -analyzeduration 100M -probesize 100M \
  
    -i WMAV.VOB \
  
    -map 0:1 -map 0:2 \
  
    -c:v libx264 -preset slow -tune film -crf 21 \
  
    -c:a aac -b:a 192k \
  
    wmav.mkv

  However, when I include -c:a aac, I get thousands of errors like this :

  Error while decoding stream #0:2: Error number -16976906 occurred
  
  [ac3 @ 000002bd24d8eec0] expacc 127 is out-of-range
  
  [ac3 @ 000002bd24d8eec0] error decoding the audio block

  There doesn’t seem to be any issue with the audio stream since it plays back fine in VLC. The transcode succeeds if I use -c:a copy.

  What is causing this error and how could I fix the problem ?

• avformat/segafilmenc : Avoid seek when writing header

  17 juillet 2020, par Andreas Rheinhardt

  avformat/segafilmenc : Avoid seek when writing header
  Up until now, the Sega FILM muxer would first write all the packet data,
  
  then shift the data (in the muxer's write_trailer function) by the amount
  
  necessary to write the header at the front (which entails a seek to the
  
  front), then seek back to the beginning and actually write the header.
  This commit changes this : The dynamic buffer that is used to write the
  
  sample table (containing information about each sample in the file) is
  
  now used to write the complete header. This is possible because the size
  
  of everything in the header except the sample table is known in advance.
  
  Said buffer can then be used as one of the two temporary buffers used
  
  for shifting which also reduces the amount one has to allocate for this.
  
  Thereby the header will be written when shifting, so that the second
  
  seek to the beginning is unnecessary.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavformat/segafilmenc.c

• ffmpeg Produces unplayable MP4 File From avi files

  25 août 2021, par Manngo

  A have a hand full of .avi files which I would like to convert to .mp4. Cobbling together everything I have found on the Internet, I end up with something like this :

  


  ffmpeg -i something.avi -c:v copy -c:a copy something.mp4


  


  What I get is playable on VLC player, but, of course, that will play anything I through at it. However, I cannot play it using QuickLook in the Finder or with the QuickTime player.

  


  In some cases I get video, but no sound. In some other cases I get garbled video.

  


  I am guessing that the audio or video codec inside the .avi file is incompatible with MacOS, and that the copy instruction above is not appropriate. In that case I guess that I would actually need to reencode the audio or video.

  


  If this sounds incoherent, I admit I know very little about video files.

  


  What would be the best settings to try to produce an MP4 which works natively on MacOS ?