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• FFMPEG Chapter Metadata added to a song file is sometimes off by 1 second

  6 février 2021, par Elthfa

  I attempted to add chapter metadata to a .opus file, but afterward, the file metadata showed timestamps different than the ones I attempted to add.
It seems to be adding an extra second to the timestamps under certain conditions.
I'm not sure if this is a bug, or if maybe I am just using the command wrong.

  


  Here are the commands I performed :

  


  First I removed all existing metadata from the file. I did this using a command I found on stack overflow :

  


  ffmpeg -i test_song.opus -c copy -map_metadata -1 -fflags +bitexact -flags:a +bitexact no_metadata.opus


  


  Then I added the new metadata from an external file I had written :

  


  ffmpeg -i no_metadata.opus -f ffmetadata -i metadata.txt -c copy -map_metadata 1 out.opus


  


  The file 'metadata.txt' looks like :

  


  ;FFMETADATA1
[CHAPTER]
TIMEBASE=1/1000
START=0
END=400
title=400 ms
[CHAPTER]
TIMEBASE=1/1000
START=400
END=500
title=100 ms
[CHAPTER]
TIMEBASE=1/1000
START=500
END=2000s
title=1500 ms
[CHAPTER]
TIMEBASE=1/1000
START=2000
END=97000
title=The Rest


  


  When I print out the basic data from the file, not all the timestamps shown match the ones I had in the metadata file.

  


  > ffmpeg -i out.opus
...
Input #0, ogg, from 'out.opus':
  Duration: 00:01:37.00, start: 0.000000, bitrate: 147 kb/s

    Chapter #0:0: start 0.000000, end 0.400000
    Metadata:
      title           : 400 ms

    Chapter #0:1: start 0.400000, end 1.500000
    Metadata:
      title           : 100 ms
    
    Chapter #0:2: start 1.500000, end 2.000000
    Metadata:
      title           : 1500 ms
    
    Chapter #0:3: start 2.000000, end 97.000000
    Metadata:
      title           : The Rest
...


  


  You can see the issues for chapters 0:1 and 0:2, which show a start and end time of 1.5 seconds respectively, when it should be 0.5 seconds for each.
I tried several combinations for this, and it seems that if the digit in the hundreds of milliseconds place is between 5 and 9 inclusive, it adds and extra second to the timestamp it saves in the metadata.

  


  Is this due to me using the command wrong ? Or formatting the metadata file wrong ? Or is there an issue in the code with rounding timestamps ?

  


  Thanks !

  


• How can I pass chapter data to multiple streams with tee muxer

  11 février 2021, par jonnywishbone

  I'm trying to transcode several videos from their original format into 4K and 1080p HD MKV and/or MP4 containers. The original contains chapter info, but no matter how many incarnations of ffmpeg flags/settings I've tried, the chapter data doesn't wind up in either output stream.

  


  Here's a redacted version of the command I'm using (PowerShell 7.1) :
...

  


     ffmpeg -i "XXXXXxxxx.mkv" `
   -loglevel repeat+warning -stats  -hide_banner -y -benchmark `
   -flags +global_header -filter_complex `
   "[0:v]split=2[s0][s1]; `
   [s0]null[v2160]; [s1]scale=1920:-1[v1080]" `
   -to 00:01:05 -map "[v2160]" -map "[v1080]"  -map 0:1 -map_metadata 0 -map_chapters 0 -movflags use_metadata_tags `
   -c:v libx265  -x265-params  `
   "log-level=error" -pix_fmt yuv420p10le   `
  -b:v:0 3100K -b:v:1 2200K -minrate 400K -bufsize 8M  `
   -c:a:0 aac  -ac:a:0 2   -ar:a:0 48000 -af:a:0 dynaudnorm  -b:a:0 192k -disposition:a:0 default+original `
   -metadata:s:a:0 language=eng -metadata:s:a:0 title="aac-stereo" -metadata:s:a:0 handler="aac-stereo" `
   -metadata comment=" "  -metadata title=""XXXXXxxxx"  `
   -f tee "[select=\'v:0,a\':f=matroska]`""XXXXXxxxx [2160p].mkv`"|[select=\'v:1,a\':f=matroska]`""XXXXXxxxx [1080p].mkv`""


  


  ...

  


  What's the secret sauce for getting chapter info passed to the output streams ? Is it a tee select of some sort ? A different -map_metadata -type setting ?

  


  Please forgive the odd code formatting - the editor really didn't know what to do with PowerShell back-tick escape characters that delimit quotes and other literals in PS scripting !

  


• avformat/matroskaenc : Check chapter ids for duplicates

  15 mars 2021, par Andreas Rheinhardt

  avformat/matroskaenc : Check chapter ids for duplicates
  Up until now, there has been no check that each chapter has a unique id ;
  
  there was only a check for whether a chapter id is zero (this happens
  
  often when the chapters originated from a format that lacks the concept
  
  of chapter id and simply counts from zero) which is invalid in Matroska.
  
  In this case the chapter ids are offset by 1 to make them nonnegative.
  
  Yet offsetting won't fix duplicate ids, therefore this is changed to
  
  simply create new chapter uids when the input chapter uids don't conform
  
  to the requirements of Matroska (in which case it can be presumed that
  
  they did not originate from Matroska, so that we don't need to bother
  
  to preserve them).
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavformat/matroskaenc.c