Matroska: How to detect mux delays of audio streams?

[LigH]

I was afraid to post this question in the "Matroska FAQ" directly, but I'd enjoy to see it there after answering:


How can I detect a delay / skew of streams in a Matroska file?

Neither MediaInfo 0.7.7.1 nor mkvinfo (MKVtoolnix 2.2.0) will show me the delay of the audio stream I set in mkvmerge for multiplexing.
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It appears to me (looking with a hex editor into the later extracted stream) that mkvmerge inserts "silence" blocks of the appropriate audio format where known, so e.g. an AAC stream is extended by "silence" AAC blocks in front if it was multiplexed with a positive delay.

[mikeathome]

Hi,
I use MPC's ability to set a temporary audio delay, fiddle around until I am satisfied and remux.

You can try AC3TO (it'll state a delay after it's initial investigation) but I am getting from time to time (rarely) mis-statements.

mike

[LigH]

If audio streams get stuffed instead of moved (and so the original audio file won't be restored byte-identically when demuxing), no tool can be able to detect a delay.

I am just curious if I discovered that behaviour correctly.

[stax76]

Some situation for MP4, StaxRip can be setup to batch remux mp4 to mkv and vice versa but delay gets ignored because I couldn't read it with MediaInfo, mkvinfo and MP4Box. At least it's not a issue with StaxRip encoded files as it has never set aspect ratio or delay in the container using the default settings.

[TheFluff]

I see people are giving pretty good answers to questions the OP didn't ask.

If audio streams get stuffed instead of moved (and so the original audio file won't be restored byte-identically when demuxing), no tool can be able to detect a delay.

I am just curious if I discovered that behaviour correctly.

I'm pretty sure you're correct. The delay cannot be detected or (easily) reversed because it's not a container option that gets read and implemented by the splitter at playback time; instead it's a "hardcoded" delay, since mkvmerge just inserts a suitable amount of silent audio with the format in question.