this is my first post (on video.stackexchange.com).

I need some explanation regarding to re-encoding a single .ts chunk and then use cat command.

I'll explain my scenario.

I've a lot of .ts chunks that all together create a smooth video. Tested.

To create a single video I use the classic linux cat command, and everything works a treat.


These "lot of .ts chunks" reside on a web-hosting where, obviously, it is not possible to install ffmpeg, but I can use cat command (through PHP's shell_exec).

My goal is to apply an audio/video fade-in on first chunk (and so far I've done it with -vf "fade=t=in:st=0.1:d=1" and -af "afade=t=in:st=0.1:d=1") on my local machine and then, after uploaded the "faded chunk" on remote web-hosting, cat the faded chunk + remaing chunks.

My actual results

My concatenated-chunks-video has a frame-gap at the end of the "faded chunk" and the beginning of the next chunk. After this, plays smoothly.


ffmpeg -i /path/to/first_chunk.ts -vf "fade=t=in:st=0.1:d=1, format=yuv420p" -af "afade=t=in:st=0.1:d=1" -c:v libx264 -b:v 5099.998K -profile:v main -level:v 4.0 -c:a aac -b:a 279000 -strict experimental -y /path/to/first_chunk_fade_in.ts

cat /path/to/first_chunk_fade_in.ts /path/to/2nd_chunk.ts /path/to/3rd_chunk.ts /path/to/4th_chunk.ts /path/to/5th_chunk.ts > /path/to/merged.ts


All -c:v, -b:v, -profile:v, -level:v, -c:a, -b:a values were recovered and / or calculated from the original chunk using ffprobe

Any ideas? Or do I have to re-encode the whole file?

Many thanks

  • Add -copyts and check. – Gyan Apr 10 '19 at 18:52
  • I try immediately.... – Oscar Zarrus Apr 10 '19 at 18:56
  • With -copyts I lose the fade – Oscar Zarrus Apr 10 '19 at 19:10
  • Instead of st, use the start frame and sample options instead. – Gyan Apr 10 '19 at 19:48
  • same thing. Ok for fade but gap remains. I believe, however, that problem is not attributable to the video stream, but rather to the audio track. I explain to you. I open the merged file with VLC. Starting from the beginning of the stream, if I PLAY, there's the gap, but if I make a frame-by-frame (shortcut "e" on VLC), no gap occurs and everything runs smoothly. Since VLC does not handle audio on the frame-by-frame (the video becomes mute), I think it's the audio track "in some way" carries with it the video track trying to "put it in sync", creating this little hop in the junction point. – Oscar Zarrus Apr 10 '19 at 21:45

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