AC3 audio delay which is correct?

[dumbas..]

I regularly use MeGui for DVD conversion via x264. Well done to all those who created it, THANX. <advert over>:D

I notice that DVDdecryper stream info states for example:

0x80 - Audio - AC3 / 6ch / 48kHz / DRC / English / LBA: 27 / PTS: 00:00:00.280 / Delay: -80ms

Yet the AC3 file created by the D2V creator (DGIndex) produces a file called:
VTS_04_1 T01 3_2ch 448Kbps DELAY 0ms.ac3

Should I correct the delay or leave it when loading the file into MeGui for conversion into aac?:confused:

I did a seach but found no references to this exactly, sorry if this is a repeated question. Please direct me to the thread if it has been mentioned previously

[shon3i]

If you find desynch when watch movie, than you can apply that value.

[bond]

moved

[madoka]

In my experiences the differences are too small to notice. In cases where the audio delay is actually significant (+/- 5 s or more), I've yet to find a program that reliably tells me the actual delay value. In those cases, I had to resort to syncing manually.

[dumbas..]

In my experiences the differences are too small to notice. In cases where the audio delay is actually significant (+/- 5 s or more), I've yet to find a program that reliably tells me the actual delay value. In those cases, I had to resort to syncing manually.

:thanks:

[neuron2]

In cases where the audio delay is actually significant (+/- 5 s or more) Is that a typo? Did you perhaps mean 50 milliseconds?

[madoka]

Is that a typo? Did you perhaps mean 50 milliseconds?
No, I really mean offsets that are several seconds. Once in a while I'll come across a DVD where when the AC3 tracks are horribly out of sync when demuxed. It's probably caused by the newer copy protection schemes.

There are several threads in the Decrypting forum on this, and I've tried many of the suggestions. But they either don't work (maybe due to my own error), or don't work reliably. Since the focus of the forum is more on shrinking DVDs, this problem rarely arises (because the tools don't require demuxing the audio?). I guess this is why there hasn't been a more straightforward solution.

Ultimately it's faster for me to sync the audio manually (although much more annoying) than trying the handful of workarounds to see which one sticks.

EDIT: Hmm, it just occurred to me that desync only happens if I try to demux the AC3 tracks. Maybe if I use DirectShowSource() on the VOB files directly it'll be okay. I'll have to try that next time...

[bigotti5]

Dvddecrypter info is wrong in this case.
Most hardware encoders produce mpeg where the first gop has two B-frames (encoded using only backward
prediction or intra coding) as first frames (display order).
Dvddecrypter uses the PTS from first frame in decoding order (I-frame) to calculate the delay and in PAL this results in -80ms delay.