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• FFMPEG - Is there a way to remove "metadata" from .MKVs ?

  1er janvier 2019, par smirnoval

  I’ve got a Matroska Media Container file (.MKV) ; summarizing it with "MediaInfo" shows it’s gotten a few text streams (I guess they’re subtitles, although they’re not shown during VLC Media Player playback), and summarizing it with MKVToolNix shows all these ’substitles’ along other weird entries.

  I know I can use the latter program to actually "save" the .MKV file without unnecessary data (everything except the Video and Audio), but I’ve never been a fan of those kinds of tools and would like to know if there’s actually a way to remove unnecessary data with FFMPEG’s command lines. All I need is the Video and Audio datas in the .MKV to later convert it into either a HEVC or AVC codec containers.
  (if there’s a command that can do all that in one go, please let me know)

  Thanks a lot.

• How to segment a video file (using FFMPEG) to "encoded" version (i.e., .mp4 is downloaded from one our CDN servers) in which each chunk must be 4MB ?

  13 janvier 2019, par Danyal Zia

  I am using FFMPEG command-line/terminal tool. I have a video in .mp4 format. I am well educated on the segmentation of videos in terms of length/duration, however, I want to segment the chunks of the "encoded/transcoded" version of the video (which I downloaded from our CDN in.mp4) to 4MB (4000000 Bytes), except the last one, which will vary in size (i.e., to encode/decode the video fully). If I am having trouble explaining what I am seeking, then just know I have no interest in segmenting the video in terms of duration/length, as this is irrelevant for me.

  To explain the scenario : I have two copies of the same video. The one is "original" and the second video is the one that I downloaded from the server/CDN. The second video turns out to be corrupted (despite the fact that the video is downloaded successfully, and has the same length/duration) ; it stops playing around 1:12 minutes, even though the seeker/slider keeps progressing until somewhere around 1:45 minutes where the video and audio start to work again.

  I have done the binary comparison (using "fc" in CMD) of these two videos, and they are not the same at all.

  In a nutshell : I think I need to "encode" the corrupted .mp4 video, and then segment the encoded data to multiple versions of 4MB. I don’t know how can I do it from FFMPEG.

  If anything isn’t clear, then ask as many questions you want.

  Thank you for reading !

  Edit : The following seems to work, however, not all the chunks are equivalent to 4MB. What is a something I am doing the wrong way ?

  ffmpeg -i "original.mp4" -b:v 1000000 -g 60 -hls_time 2 -hls
_list_size 0 -hls_segment_size 4000000 output.m3u8

• How do I fix the "PES packet size mismatch" error in FFmpeg ?

  8 février 2021, par Ed999

  How to fix the error PES packet size mismatch in FFmpeg -

  



  I'm going to answer my own question, because the phrase PES packet size mismatch comes up regularly in posts relating to ffmpeg, but I've nowhere seen a satisfactory solution to it.

  



  It usually figures in a problem involving .TS transport stream files : either in relation to concatenating such files, or relating to re-muxing them (from .ts to .mp4). Somewhere in the output from ffmpeg, the deadly phrase packet size mismatch will suddenly start repeating.

  



  A solution is to concatenate them as .ts files (i.e. in their original format), then take the output .ts file, split it into a video file (.ts) and an audio file (.ts), then remux them (to either .ts or .mp4) using the "itsoffset" option. Even if stream copy is used, outputting to .mp4 will often give worse picture quality than retaining the .ts format.

  



  The following code does that, outputting either .mp4 video or .ts video (copy the code into a simple .bat batch file, then run that file) -

  



  .

  



  :: Program Location
SET ffmpeg="C:\Program Files\FFmpeg\ffmpeg.exe" -hide_banner  


::  STEP 1 -

::  Create File List
IF EXIST mylist.txt DEL mylist.txt
FOR %%i IN (*.ts) DO ECHO file '%%i'>> mylist.txt

::  Concatenate Files : TS
%ffmpeg%  -f concat  -safe 0  -i mylist.txt  -c copy  -threads 1  out.ts


::  STEP 2 -

::  Extract Video stream
%ffmpeg%  -i out.ts  -vcodec copy  -an  -sn  -threads 1  video.ts

::  Extract Audio stream
%ffmpeg%  -i out.ts  -acodec copy  -vn  -sn  -threads 1  audio.ts


::  STEP 3 -

::  Combine Video and Audio streams (with .MP4 options)
SET mapping=-i video.ts -itsoffset -0  -i audio.ts   -map 0:v -map 1:a
SET options=-flags global_header  -movflags faststart  -threads 1
%ffmpeg%  %mapping%  -c:v copy -c:a copy  %options%  output.mp4

::  Combine Video and Audio streams (with .TS options)
SET mapping=-i video.ts -itsoffset -0  -i audio.ts  -map 0:v -map 1:a
SET options=-threads 1
%ffmpeg%  %mapping%  -c:v copy -c:a copy  %options%  output.ts


  



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  Addendum :

  



  There seems to be some dispute about my suggested solution, as detailed in the Comments below. It seems to be being said that my solution is ignoring the fact that data is missing in the source files.

  



  I think the least I can do is admit that since ffmpeg is reporting an error in the source files, with its 'packet size mismatch' warning, the objection raised in the Comments might be valid.

  



  However, even if data is missing, my suggested routine will at least give you a file which will play in most media players. In many cases, there will not even be an audible or visual fault at the join point specified in the reported error.

  



  It's difficult to see how the missing data might be restored, but do please chip in with suggestions. There must be scope for improving my script, because so little attention has been paid to this type of fault previously.

  



  Happily, it seems that this type of error will NOT cause the sound to lose synchronisation with the picture. So the audio after the join-point will not go out-of-sync, even if some data is missing at the join.