Audio Delay

[m00511]

Hi all , i need to delay audio in order to sync it with video but when i did it with ffmpeg or mkvtoolnix the video will start from the delay means when i delay audio in 20 sec the video starts from 20 and before that video is broken with glitch , how can i fix it? thanks

[sneaker]

20 seconds positive or negative audio delay? What audio format are you using? If your player can't handle 20 seconds positive audio delay it might be best to extract the audio, prepend 20 seconds of silence to it and then mux without delay.

[JVRaines]

What is your FFmpeg command line?

[m00511]

20 seconds positive or negative audio delay? What audio format are you using? If your player can't handle 20 seconds positive audio delay it might be best to extract the audio, prepend 20 seconds of silence to it and then mux without delay.

actully it dosent matter , both positive and negative result is like this
[Attachment 46663 - Click to enlarge]
how can i prepend 20 seconds of silence?

[m00511]

What is your FFmpeg command line?

ffmpeg version N-90313-gb173e03536 Copyright (c) 2000-2018 the FFmpeg developers

[JVRaines]

No, not version. What FFmpeg command line are you executing?

[poisondeathray]

If that 20 seconds of video is "broken with glitch", why don't you cut off that 20 seconds of video

[Bernix]

Don't you apply delay to video track in mkvtoolnix?
Weird, I think it shouldn't have impact to video, messing with audiotrack.


Bernix

[m00511]

If that 20 seconds of video is "broken with glitch", why don't you cut off that 20 seconds of video

because the video will be Incomplete , actully at this time the video doesnt need audio and if i add a 20 second of silent audio it will be ok

[m00511]

Don't you apply delay to video track in mkvtoolnix?
Weird, I think it shouldn't have impact to video, messing with audiotrack.


Bernix

it's the same, the video will start from 20 sec and before that is broken

[m00511]

No, not version. What FFmpeg command line are you executing?

oh yes,

ffmpeg.exe -i "movie.mp4" -itsoffset 3.84 -i "movie.mp4" -map 1:v -map 0:a -c copy "movie-video-delayed.mp4"

ffmpeg.exe -i "movie.mp4" -itsoffset 3.84 -i "movie.mp4" -map 0:v -map 1:a -c copy "movie-audio-delayed.mp4"

something like this

[sneaker]

Add "-report" to the ffmpeg command line and upload the complete, unaltered log file that is created. Are you really inputting the very same file ("movie.mp4") twice or you supplying 2 different files? Cutting away video can be dangerous because of the keyframe/non-keyframe GOP structure video typically has. Shouldn't have such problems with audio (second example).

[JVRaines]

It's necessary to input the same file twice because the itsoffset option cannot be applied per-stream. The map options select appropriate streams for remuxing.

For audio delay, you can use the adelay filter and it will pad silence.