Muxing AC3 with delay into an AVI

[JimmyBarnes]

I want to rip my DVD to AVI

I extract the AC3 stream and see it has delay -40ms

When I mux the AC3 into the video stream using Virtual Dub Mod 1.5.10.2, for "Audio skew correction, Delay audio track by" do I enter 40 ms or -40 ms

An explanation of why to do what would be appreciated

TIA

[tebasuna51]

The best option is use DelayCut or eac3to to apply the delay over the .ac3 and after mux with VDM without delay.
Then true ac3 frames are cutted or added (silenced) in 32 ms steps (ac3 frame duration)

You can use the VDM with -40 but isn't a true delay (only padding 0's or ac3 cutted frames) and you can have problems with some players (PS3, ...)

BTW 40ms is only a video frame and can't see async problems (until 100ms is ok)

[Inspector.Gadget]

AFAIK AvimuxGUI uses a different muxing delay method than VDub and should be able to do what tebasuna51 suggests with true AC3 frames in a single step.

[JimmyBarnes]

The best option is use DelayCut or eac3to to apply the delay over the .ac3 and after mux with VDM without delay.
Then true ac3 frames are cutted or added (silenced) in 32 ms steps (ac3 frame duration)

You can use the VDM with -40 but isn't a true delay (only padding 0's or ac3 cutted frames) and you can have problems with some players (PS3, ...)

BTW 40ms is only a video frame and can't see async problems (until 100ms is ok)

Supposing the AC3 delay was -100 ms. Then using VDM (please humour me), I would enter -100 ms not +100 ms for "Audio skew correction"?

Excuse me if this seems obvious to you, but it is something which confuses me greatly

[tebasuna51]

If delay -40ms, I say -40
If delay was -100 ms then -100

[JimmyBarnes]

If delay -40ms, I say -40
If delay was -100 ms then -100

According to VDM: "Use positive values if the audio is playing too early, and negative values if the audio is playing too late."

So -100 ms will in fact advance the audio AHEAD of the video, that is, a NEGATIVE DELAY, which in fact is an ADVANCE.

I guess my real question is then: Is the "AC3 delay" used in the same sense as "Audio skew correction", a positive delay actually delaying audio relative to video and vice versa.

[tebasuna51]

According to VDM: "Use positive values if the audio is playing too early, and negative values if the audio is playing too late."
Correct
...
I extract the AC3 stream and see it has delay -40ms
...
How do you 'see' the -40ms delay?
You can't ear if is playing 40ms too early or too late.
If you use a tool like DGIndex the delay is in the name of ac3 file, and mean than you must cut the first 40ms because 'the audio is playing to late'
I guess my real question is then: Is the "AC3 delay" used in the same sense as "Audio skew correction", a positive delay actually delaying audio relative to video and vice versa.
Yes