mkvtoolnix - delay by a fraction of a ms

[maudit]

hi, I have this doubt since a while.
can I delay and audio track in mkvtoolnix by a fraction of a millisecond?
for example not 5, not 6, but 5.2 or 5.4?
is it possible? it accept integers only? comma and dot return errors..

how do I write it?

[Selur]

Out of curiosity: What for?

it accept integers only? comma and dot return errors..

yes, that is correct

is it possible?

No (at least not unless you write your own code to create/modify mkv containers)

[maudit]

Out of curiosity: What for?

cause I'm a perfectionist at a phenomenological level. XD
jokes apart, sometimes I want the audio is perfectly in sync, I mean visually, even if no one can detect the out of sync with their ears.

got it, thanks!

[Ennio]

What am I not understanding here? To me, A/V sync always depends on at what moment you perceive image and sound. Ignoring speed of light, sound-speed travels at approx. 343 m/s. A tenth of a millisecond would mean a difference in distance of 34.3 mm, if I'm correct. So during real-life listening, your ears should stay in such exact range to be synced within that precision. Move your head and you're "off".

So, what do you mean with "visually perfect in sync"? And is there a way how to determine this, within a 0.1 ms (or any, for that matter) accuracy?

[Selur]

@maudit: What tool would you use to check that delay? (to be frank I know of no tool which a. visualized such delays or b. is even that accurate)
Now that I think of it: one could adjust the a/v delay by manipulating the timecode file of the stream.
Also read https://www.matroska.org/technical/notes.html -> so it's possible, but you would have to manually edit the time stamps.

Cu Selur

[maudit]

So, what do you mean with "visually perfect in sync"? And is there a way how to determine this, within a 0.1 ms (or any, for that matter) accuracy?

I mean I open 2 vdub2 windows, I arrange them side by side, then I zoom in the audio wave display, and 1ms can be 10 or 20 pixels or so.

@maudit: What tool would you use to check that delay?

vdub2, thanks for that hint, I'll look at it, but for the moment I think I can just try to use
DelayAudio(clip, float seconds)
in case I need more precision.

[Selur]

LOL, last I checked, neither VirtualDub nor VirtualDub2 always correctly read the delay correct.
iirc. then I used a mp4 container and reported possible issues to the gpac dev and the result was that the file was right, but neither VD version did display the delay properly, so I would not reply on that visualization too much. (especially with anything other than wav audio)

[maudit]

LOL, last I checked, neither VirtualDub nor VirtualDub2 always correctly read the delay correct.

I have no doubts that vdub2 could sometimes visualize the wave in an uncorrect position, with certain files/audio types.
that's why I usually recheck it by refreshing, re-selecting the audio track.
but for most of the cases it works properly, the sync is correct and if for example I add 1ms in toolnix or in the script,
the vdub2 wave audio display, correctly moves by 1ms.

I sometimes double check it too by using avisynth+ waveform command in avspmod,
and I didn't notice any discrepancies since now, except maybe very few cases.

[Selur]

but for most of the cases it works properly, the sync is correct and if for example I add 1ms in toolnix or in the script,
the vdub2 wave audio display, correctly moves by 1ms.

That does not mean it properly detects the input sync.