Sur d’autres sites (5170)

• avcodec/rkmppdec : Use RefStruct API for references to decoder itself

  24 septembre 2023, par Andreas Rheinhardt

  avcodec/rkmppdec : Use RefStruct API for references to decoder itself
  Avoids boilerplate code when creating the context
  
  and avoids allocations and therefore whole error paths
  
  when creating references to it. Also avoids an indirection
  
  and improves type-safety.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] libavcodec/rkmppdec.c

• avcodec/ass,webvttdec : implement more portable curly brace escapes

  19 février 2024, par Oneric

  avcodec/ass,webvttdec : implement more portable curly brace escapes
  Unlike what the old comment suggested, standard ASS has no character
  
  escape mechanism, but a closing curly bracket doesn't even need one.
  For manual authored sub files using a full-width variant of an
  
  appropriate font and with scaling and spacing modifiers is a common
  
  workaround.
  
  This is not an option here, but we can still make things much less bad.
  
  Now the desired opening bracket still shows up in libass, and
  
  standard renders will merely display a backslash in its place
  
  instead of stripping the following text like before.
  

  • [DH] libavcodec/ass.c
  • [DH] libavcodec/webvttdec.c
  • [DH] tests/ref/fate/sub-webvtt

• ffmpeg audio out of sync with video stacking

  3 avril 2024, par s0mbre

  The problem

  


  When trying to do horizontal stacking of two videos in ffmpeg, the combined audio track loses sync with the video on the second input. As far as I've look it up, this problem is very common, not to say notorious with ffmpeg.

  


  I do hstack muxing like this :

  


  ffmpeg -i 1.mp4 -i 2.mp4 -filter_complex \
"[0:v]scale=1280:-2,crop=w=640:h=720:x=0[v1]; \
[1:v]scale=1280:-2,crop=w=640:h=720:x=0[v2]; \
[v1][v2]hstack=shortest=1[v]; \
[0:a][1:a]amix=duration=shortest[a]" \
-map [v] -map [a] -c:v libx264 -c:a libmp3lame -r 30 -y stuff/out.mp4


  


  It encodes just fine as far as the hsplit goes. But the resulting video is out of sync with the audio : the second input (located on the right side in the resulting split) demonstrates about 3 sec. audio off-syncking, where the audio track is ahead of the picture. I realize this is somehow connected with the source videos' timestamps, but no popular remediation recipes helped (see below).

  


  What I expect

  


  I'd expect a resulting stacked video where the audio track is muxed with exact correspondence to the original input pictures.

  


  What I tried (all in vain !)

  


  Something I've tried but to no avail :

  


  

  1. Appending -async 1 option as suggested here and here

  


  2. Using the aresample=async=1 or aresample=async=1000 filter on each audio input as suggested here and here

  


  3. Padding each audio track with apad as suggested here

  


  4. Using the adelay=0 and adelay=[delay]s filters on the failing input

  


  5. Changing the audio codec to a number of alternatives (aac etc.)

  


  6. Infinite combinations of 1-5 above...

  


  


  What seems indeed to work is manual passing a delay value to the -itsoffset filter as suggested here and in the docs and using the offset track as an extra (pure audio) input. But how do I find the exact offset with a different set of videos ?

  


  In short, I am at a standstill after 7+ days of ravenous search-and-try.