Audio delay offset still needed?

[Toon_Junkie]

Hi,

Quick question. I know that you used to have to enter a delay offset long ago (ok, maybe 7 or 8 months) when you where ripping and encoding, but I haven't seen it mentioned anywhere for a while.

I was trying out DVD2SVCD just to see how he does things (and maybe pick up some pointers) and I notice the program ajusts the audio.
Audio delay: -100 ms
Adjusting audio delay.
Wav Conversion Finished
So, my question is, does the audio need to be adjusted if you do not use DVD2SVCD? If so, how does one acomplish this these days? Does anyone know how DVD2SVCD is doing it? (I have a feeling it's an internal routine).

My normal method is to use DVD2AVI, extract audio with Graphedit, AVISynth with CCE (using TRIM to cut up the movie into CD sized sections), encode the audio with TMPG (using the avs files as the input) and then mux together with BBMPG.

Thanks

[24hourloop]

You adjust the offset when muxing with bbMPEG. You can enter an audio offset at the bottom.

[smiller667]

You _always_ have to take audio delay into consideration (a DVD of Shanghai Noon had 22secs (!) delay) ... dvd2avi gives you the delay in the filename of the demuxed audio.
The other thing is the pack or movie startup delay which you can specify in bbmpeg - a delay of 2 secs can fix A/V sync issues for standalones.

[Toon_Junkie]

OK guys,

Thanks for the feedback. I understand that you can do this with BBMPEG but my point is it's not mentioned anywhere (anywhere I can find anyway) in the guides on Doom9's site anymore (I followed the DVD2AVI guide using CCE). Unless of course I have missed it, in which case can someone point it out.

So... again the question is, do you need to do it anymore? Why is DVD2SVCD doing it?

I have done many conversions using very similar steps and have had very little problems with sync.

thanks,

[24hourloop]

I have several ideas why not:

a.) I don't understand Doom9's preoccupation with the Intervideo codec altogether. The compression is much too heavy for your home stereo. However, if you do the Surround downmix (or decoding) to AVI using DVD2AVI it already adjusts for the offset. I like the sound it produces and it is fool-proof.

b.) I can only surmise he has forgotten about it. While you can do a variety of movies and never discover the fact (it has to be off by more than say 60msec to be noticeable) it is still necessary. The same problem exists everywhere when you go from AC3 to MP2. This problem exists when you work with Azid/BeSweet, any of these tools. You have to take the offset into consideration.

Maybe Doom9 can comment why he removed this section?

[Doom9]

the largest part of the svcd guides is rather old (check the last updated stamp)... at the time I wrote the bulk of it my prefered method of audio encoding was graphedit which never gave me any synch problems so I figured it wasn't necessary. I know it's necessary if you use azid though but no svcd guide contains that method and dvd2svcd does the adjustment automatically.

if you check recent guides (that's divx stuff mostly) there I use azid and the offset stuff is mentioned.

also.. I had a talk with dvd2svcd the other day.. the reason why he's using wla to make the offset adjustment prior to muxing is for people who like to mux on their own. That I don't quite get as if you step out of the paved road you have a tougher journey, but basically he agrees that it would be sufficient just to take the offset from the ac3 and add it into the appropriate bbmpeg field during muxing.

why not using the internal decoder? well.. rumor has it that the azid solution is better and that ssrc is THE downsampler to use. Furthermore.. with besweet you can now do the whole processing in float mode without intermediate files.. which means no problems about > 2gb wavs, and the highest possible quality so this might eventually make it into the guides. But you know.. there's so many guides and so little time to update them all so things really take their time. imho dvd2svcd seems to be the hottest program in dvd -> svcd conversion these days so this has the priority when it comes to updating the guide.

[Toon_Junkie]

OK.. now we're getting to it.

I use the graphedit method, and too have had very little problems. Usually just those DVDs that have a studio logo without audio, but DVD2AVI thinks the audio starts with the logo.

So, it would seem that I am just luckily working with DVDs that don't have a big offset. I will look through those divx guides again.

I agree that DVD2SVCD is about the hottest thing going these days. I run through a couple just to see what's going on and how he does things.

I always segment my encodes by using TRIM() in the AVS files, it never even occured to me to use BBMPEG until I sat and watched a DVD2SVCD session (hours of boredom with minutes of excitement :)).

Thanks for the answers and the suggestions. I will be looking more closely for sync issues. Anyone know how to get nose prints off a monitor? ;)

Cheers

[Doom9]

how do you rip? never had any problem with studio logos.. if they're not i nthe same pgc they should be stripped out during ripping (for that I always use vstrip.. been one of the most useful tools since the ripping stoneage).

[Toon_Junkie]

doom9

I rip using SmartRipper, then DVD2AVI.

The logo thing was a real odd duck. Only happened once or twice. It was real obvious because the audio was ahead by about 2 or 3 whole seconds, not just a msec or 2. I can't remeber the titles right now, but you would know it if it happened.

I took a quick run through the guides and the only place I saw about setting the offset was in the Gknot guide. I noticed that your samples in the AC3-MP2 and AC3-MP3 show an AC3 with 0ms offset (lucky duck). Any more information on where in Azid to adjust? Or is it after Azid has finished with it that you use another program?

So, if I'm using graphedit, then I should do the offset in BBMPEG as I mux?? or is there a small program that will adjust the whole wav file at once?

Is wla what DVD2SVCD is using to run the offset? I took a look at that proggy and it looks like it's only for adjusting the sampling rate.

Thanks

[Toon_Junkie]

ok...

so, if I have a audio file like so
test AC3 T01 3_2ch 448Kbps DELAY -99ms.ac3
that would mean the audio starts 99ms before the video?

So in BBMPEG I would Startup Delay -> audio1 take off 99ms (180-99=81)?

Is that right?