mkvmerge - can't move audio foward with delay option

[cpaqf1]

Hi,

I have about 100 mp4 files that need the exact same amount of audio delay applied (-250ms) I also want the end products in mkv, if I transcode them from mp4 to mkv, according to MediaInfo they already have -42ms when so they'd need -292ms in total? Problem is, whenever I run them through MKV merge, even if I put in -250, MediaInfo then says something like -36ms, so it doesn't want to apply negative delays, positive delays work perfectly though.

any ideas?

thanks

[sneaker]

mkvmerge may delete samples so the value you see after the conversion in MediaInfo may not be the delay that was actually applied. This only happens with negative delays. You have to decode in e.g. a wave editor and manually measure if the delays add up to your desired value. You may also use the display statistic tags written by mkvmerge as hints. You can read them using mkvinfo. The track duration will be shortened according to the length of the deleted samples.

Example.
Mux sample A without specifying delay in mkvmerge. Mux sample B while setting "delay" to "-250"ms. Source audio delay according to MediaInfo: -42ms.

Sample A:
Delay according to MediaInfo: -42ms.
Audio track duration according to mkv tag written by mkvmerge: 00:03:00.160

Sample B:
Delay according to MediaInfo: -36ms.
Audio track duration according to mkv tag written by mkvmerge: 00:02:59.904

Math:
00:03:00.160 - 00:02:59.904 = 256ms
256 ms + 36ms - 42ms = 250 ms
And -250ms was the delay we set so it adds up exactly.

[cpaqf1]

mkvmerge may delete samples so the value you see after the conversion in MediaInfo may not be the delay that was actually applied. This only happens with negative delays. You have to decode in e.g. a wave editor and manually measure if the delays add up to your desired value. You may also use the display statistic tags written by mkvmerge as hints. You can read them using mkvinfo. The track duration will be shortened according to the length of the deleted samples.

Example.
Mux sample A without specifying delay in mkvmerge. Mux sample B while setting "delay" to "-250"ms. Source audio delay according to MediaInfo: -42ms.

Sample A:
Delay according to MediaInfo: -42ms.
Audio track duration according to mkv tag written by mkvmerge: 00:03:00.160

Sample B:
Delay according to MediaInfo: -36ms.
Audio track duration according to mkv tag written by mkvmerge: 00:02:59.904

Math:
00:03:00.160 - 00:02:59.904 = 256ms
256 ms + 36ms - 42ms = 250 ms
And -250ms was the delay we set so it adds up exactly.

I didn't even think to check them haha.

thanks a lot