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• PGS subtitle track is out of sync after extracting then adding to another video file

  23 décembre 2022, par Diericx

  I have the Japanese and English version of a show. I am attempting to extract the subtitles and audio from the English version and add them to the Japanese version.

  


  The video in both files seems to be exactly the same.

  


  Here is the info for the streams contained in the english file. When playing this source video file Track 2 subtitles seem to be almost empty while Track 1 contains all of them forced.

  


  Stream #0:1(eng): Audio: dts (DTS-HD MA), 48000 Hz, stereo, s32p (24 bit) (default)
    Metadata:
      title           : Stereo
      BPS-eng         : 1572054
      DURATION-eng    : 00:29:08.789333333
      NUMBER_OF_FRAMES-eng: 163949
      NUMBER_OF_BYTES-eng: 343648948
      SOURCE_ID-eng   : 001100
      _STATISTICS_WRITING_APP-eng: MakeMKV v1.17.2 darwin(arm64-release)
      _STATISTICS_WRITING_DATE_UTC-eng: 2022-12-18 02:20:00
      _STATISTICS_TAGS-eng: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES SOURCE_ID
  Stream #0:2(eng): Audio: dts (DTS), 48000 Hz, stereo, fltp, 1536 kb/s
    Metadata:
      title           : Stereo
      BPS-eng         : 1509000
      DURATION-eng    : 00:29:08.789333333
      NUMBER_OF_FRAMES-eng: 163949
      NUMBER_OF_BYTES-eng: 329865388
      SOURCE_ID-eng   : 001100
      _STATISTICS_WRITING_APP-eng: MakeMKV v1.17.2 darwin(arm64-release)
      _STATISTICS_WRITING_DATE_UTC-eng: 2022-12-18 02:20:00
      _STATISTICS_TAGS-eng: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES SOURCE_ID
  Stream #0:3(eng): Subtitle: hdmv_pgs_subtitle
    Metadata:
      BPS-eng         : 22140
      DURATION-eng    : 00:28:47.454895833
      NUMBER_OF_FRAMES-eng: 836
      NUMBER_OF_BYTES-eng: 4780741
      SOURCE_ID-eng   : 001200
      _STATISTICS_WRITING_APP-eng: MakeMKV v1.17.2 darwin(arm64-release)
      _STATISTICS_WRITING_DATE_UTC-eng: 2022-12-18 02:20:00
      _STATISTICS_TAGS-eng: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES SOURCE_ID
  Stream #0:4(eng): Subtitle: hdmv_pgs_subtitle
    Metadata:
      BPS-eng         : 1770
      DURATION-eng    : 00:28:39.655437500
      NUMBER_OF_FRAMES-eng: 62
      NUMBER_OF_BYTES-eng: 380532
      SOURCE_ID-eng   : 001201
      _STATISTICS_WRITING_APP-eng: MakeMKV v1.17.2 darwin(arm64-release)
      _STATISTICS_WRITING_DATE_UTC-eng: 2022-12-18 02:20:00
      _STATISTICS_TAGS-eng: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES SOURCE_ID


  


  I extract the english audio

  


  ffmpeg -i s01e01_ja.mkv \
-muxdelay 0 \
-map 0:1 \
-vn \
-acodec copy \
s01e01_en_audio.dts


  


  I extract the english subtitles

  


  ffmpeg -i s01e01_en.mkv \
-muxdelay 0 \
-map 0:3 \
-vn \
-c copy \
s01e01_en_sub.sup


  


  I add the english audio track to the japanese video

  


  ffmpeg -i s01e01_ja.mkv \
-i s01e01_en_audio.dts \
-muxdelay 0 \
-map 0 \
-map 1:a \
-c copy \
-shortest \
s01e01_en_ja.mkv


  


  And finally add the english subtitles to the new japanese video that contains english audio

  


  ffmpeg -i s01e01_en_ja.mkv \
-itsoffset 6 \
-i future_boy_conan_s01e01_en_sub.sup \
-muxdelay 0 \
-map 0 \
-map 1:s \
-c copy \
-shortest \
s01e01_en_ja_subs.mkv


  


  As you can see I need to offset the subtitles by 6 seconds in order to get the subtitles to sync with the audio. The english audio is in sync with the video.

  


  I do not know how to debug this in order to tell if the subtitles are extracted or injected incorrectly causing the time offset. Any help would be appreciated !

  


• ffmpeg, how to avoid audio drift when muxing audio and video

  1er mai 2023, par Monkeybus

  I use scrcpy to mirror my Android screen to my PC. I have to capture the audio via bluetooth.

  


  The result is two files. One .mkv and one .aac. They are both of equal length, possibly a second or two out.

  


  I mux them together, but the audio always drifts.

  


  I mux them together with the following command, $show is the bash variable for the video file.

  


  ffmpeg -i $show.mkv -ss -00:00:02 -i $show.aac -c:v copy -c:a copy -shortest $show.muxed.mkv


  


  The -ss sets the audio start time. I generally have to play around with this on a vid by vid basis. I can generally match the audio and video perfectly at the beginning of the file, but the audio will always drift over the course of the video.

  


• ffmpeg concatenate videos - what metadata needs to match [duplicate]

  13 juillet 2022, par yarrichar

  I am trying to concatenate videos that can come from a variety of sources.

  


  I was just using the -f concat option, but this runs into issues when the formats don't watch.

  


  I can use the filter_complex option (as described in the wiki - https://trac.ffmpeg.org/wiki/Concatenate) but this is much slower.

  


  What metadata (codec, bitrate, fps, etc) needs to match so that I can use the faster -f concat option to join the videos ? My understanding here is not great atm.