help fix delay on one channel (5.1)

[geextah_2]

Hi, I have a problem with audio delay. I split the channels from a 5.1 movie track. Extract the center channel, make some VST adjustments and then remerge all channels back into the 5.1 movie track. The problem is that those VST changes add a 51 miliseconds delay to the center channel which remerged with the other audio channels sounds like echo or delay. How can I make an adjustment/recompensation for that in ffmpeg? I need to cropp the first 51ms. So he starts reading the center channel not from 0 but first after 51 miliseconds.

using

-ss 51ms -i "K:\out.wav"

fixed the echo, but this introduces the first half second of the video to sound weirdly, you can hear like the audio is swtiching. So this isn't a perfecect solution. When I cropped the audio manually this wasn't the case.

-itsoffset isn't working on audio

This is my script.

-i "K:\out.wav"

is the center channel track that needs this delay adjustment.

ffmpeg ^ 
-i "%~n1.mkv" -i "K:\out.wav" ^ 
-lavfi "[0:a:m:language:ger]pan=stereo|c0=c2+0.6c0+0.6c4+c3|c1=c2+0.6c1+0.6c5+c3[a1];[0:a:m:language:ger]channelsplit=channel_layout=5.1[FL][FR][FC][LFE][SL][SR];[FL][FR][FC][LFE][SL][SR][1][1]amerge=8,channelmap=0|1|7|3|4|5:5.1,pan=stereo|c0=c2+0.6c0+0.6c4+c3|c1=c2+0.6c1+0.6c5+c3[a2];" -map 0:v:0 -map [a1] -map [a2] -c:v copy -c:a ac3 -b:a 160k -ar 44100 -sn -dn ^ 
"G:%~n1.mkv"

Thank you for any help

[ProWo]

Try

ffmpeg -i center_channel.wav -ss 0.051 -c copy -output_ts_offset 0 output.wav

Then merge the channels

[pandy]

Use https://ffmpeg.org/ffmpeg-filters.html#adelay

[geextah_2]

adelay seems to add delay, a need the opposite of that like hasten

[pandy]

delay OTHER channels then - also it should be possible to perform negative delay (i.e. advance audio) but it will be performed in similar fashion i.e. by introducing delay on other channels.

This can be useful too https://ffmpeg.org/ffmpeg-filters.html#setpts_002c-asetpts