Audio encoding and delays...

[ArdenDag]

Hello,

I'm a little confused about one thing regarding dvd rip audio encoding, and delays. When DGIndex strips the audio from a dvd, it lists delay numbers, which need to be used when muxing a video so it syncs with the audio correctly. I understand that. However, when I encode the audio using BeLight, or MegUI, the audio encoder fills or cuts audio when encoding, but leaves the DELAY -xxxms in the file name. Does that mean that it fixes the delay, then when muxing, it 'fixes' it again? It's a little confusing. If the audio encoder is fixing the delay, shouldn't it change the DELAY to 0ms? Or am I missing something?

Thanks,
Arden

[Hobojobo]

http://forum.doom9.org/showthread.php?t=119467

[ArdenDag]

Ok, read through the thread... Lots of replies fading in and out over a year's time! But I'm still confused:

Doom9 states:
"Has nobody ever looked at the audio configuration dialog after loading an audio source? Did nobody notice that if the filename contains a delay, that the delay checkbox automatically gets checked and the value field has the value from the filename?
This is done independently for every audio track you load."

Does this mean that the muxer in MeGUI applies the delay in the filename, even if the audio was transcoded with another program, and a delay already applied? I use BeLight, and when it transcodes to fix a delay, it does NOT change the filename. Do I uncheck the delay box in BeLight or MeGui so it doesn't get done twice?

Thanks
Arden

[tebasuna51]

Does this mean that the muxer in MeGUI applies the delay in the filename, even if the audio was transcoded with another program, and a delay already applied?
Yes, because Megui don't know if the delay is already applied. Only the filename keep this info, then ...

I use BeLight, and when it transcodes to fix a delay, it does NOT change the filename.
True, but if you apply the delay, you can modify the output name to ... DELAY 0ms (is not automatic), or ...

Do I uncheck the delay box in BeLight or MeGui so it doesn't get done twice?
Yes, uncheck the MeGui delay box, if the audio name preserve the DELAY xxxms already corrected by BeLight, or you have a wrong double delay.

Always use the delay in audio conversion (if you need convert the audio) because is more precise. With a 48000 Hz audio when you decode from original format, and before convert to desired format, you have the uncompressed audio with samples of 1/48000 sec (0.02 ms) and you can cut/add audio with high precision. Furthermore you guarantee the silence added (if + delay) is encoded with the same parameters than the rest of audio (the muxer's can't guarantee this).

After converted to new format you can cut/add only audio frames (24 ms for mp3, 32 ms for ac3, ...) and the muxer's not always work fine with all audio codecs, bitrates, channels, ...

[madshi]

Easiest thing is to use delaycut directly after demuxing to apply the needed audio delays. When you've done that, rename the files so that the "DELAY +/-xxxms" is gone. That way there can be no problems with double processing or anything like that.

BTW, if you have the physical DVD disc I recommend to use DVDDecrypter in IFO mode. This way you'll get proper handling for multi angle and seamless branching DVDs, while DGIndex doesn't handle those special cases very well, I believe (someone correct me if I'm wrong, please).

P.S: Cross post with tebasuna51. Of course he's right: If you need to reencode the audio, anyway, then you should apply the audio delay there because the delaying is more exact there. However, if you don't need to reencode the audio then I'd still recommend a tool like e.g. delaycut.

[ArdenDag]

Thanks much for the help!

I kinda had a feeling it got done twice if I didn't uncheck one of my delays. I've been unchecking the delay during audio transcoding, I guess I'll reverse that to the muxing. Doesn't matter to me :)

I won't be doing much encoding with native audio from a DVD, so I won't worry about just fixing delays without transcoding for the moment.

Arden