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Old 6th May 2016, 01:03   #1  |  Link
lolmaster
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MKVextract with Audio Delays

gMKVExtractGUI add the audio delay into the extracted file name. So is MKVExtractGUI2 and MeGUI File Indexer.

Is there a simple way to do this with MKVextract CLI ?

Thank you!
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Old 6th May 2016, 08:53   #2  |  Link
sneaker_ger
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It can be done but it's not simple. You can get the delay (<= 10 seconds) from mkvmerge identification, mkvextract timecodes extraction or mkvinfo. All three require some parsing magic. (I believe a number of other programs use MediaInfo to get the delay.)
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Old 6th May 2016, 11:36   #3  |  Link
hello_hello
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Keep in mind, at the moment gMKVExtractGUI is the only program (as far as I know) that takes any video delay into account when it writes the audio delay.
There's no such thing as a negative delay for MKVs, but occasionally you'll see MediaInfo report a negative audio delay relative to the video, which means there's really a positive video delay. If an MKV has a positive video delay and a positive audio delay, gMKVExtractGUI writes the difference between the two as the audio delay when extracting.

As an example or two, if there's a 33ms video delay and no audio delay, MeGUI's File Indexer would write 0ms for the audio delay. gMKVExtractGUI would write -33ms.
If there's a 133ms video delay and a 100ms audio delay, MeGUI's File Indexer would write 100ms for the audio delay. gMKVExtractGUI would write -33ms.

MKVs with video delays aren't super common, but they exist so they're worth looking out for. They sometimes appear after remuxing MP4s as an MKVs. I've never really understood MP4 delays. MediaInfo doesn't seem to reliably display them.
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Old 7th May 2016, 05:25   #4  |  Link
lolmaster
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Thanks friends!
Looks like too complex for me
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Old 7th May 2016, 07:16   #5  |  Link
hello_hello
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It's just that normally when you re-encode video, it'd probably be under the assumption there's no video delay, so if there is one in the source file, the audio should be offset accordingly to compensate. That's what gMKVExtractGUI does when works out the audio delay.

As I said though, video delays in MKVs aren't particularly common, but they can exist so it's something to be aware of.
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