AC3 or MP2?

[dea]

Hi everyone

I quicky for ya'll,
I'm authoring a music dvd with performance collected from the internet as both mpg files and avi.

The whole thingy is seems to be working fine (after some tremendous help from some people here at doom9s forum, thank you!), but I do have one more question;
Wich format should I use, ac3 or mp2? Is there any diffrence at all when the media is already compressed?
To get my AC3 I'll have to run the mp2 thru AC3Machine, do I loose quality here?
The bitrate is somewhere in between 256-384, depending on the diffrente files.

I also need this dvd to be in NTSC, I've read somewhere that mp2 has a probably working on ntsc and that you need to have a ac3.. is this true?

Thank you in advance!
/Andreas

[Malcolm]

look at this thread: Encode to mp2 or ac3 for dvd? (http://forum.doom9.org/showthread.php?s=&threadid=81003)

btw. there is a 'search' button on top of every page...

greetings,
Malcolm

[SeeMoreDigital]

Originally posted by dea
I'm authoring a music dvd with performance collected from the internet as both mpg files and avi.

Andreas, please read the forum rules again. We do not help people who have downloaded non-paid-for media from the internet.


Cheers

[dea]

malcolm: i've searched the forum but the " " function don't seem to work, so I only got a whole lot of search results of "ac3" and "mp2", nog "ac3 or mp2" results.
But cheers for the linked thread.

SeeMoreDigital: Okey. Sorry, didn't know that captured videos from TV goes for this too.

[SeeMoreDigital]

Originally posted by dea
SeeMoreDigital: Okey. Sorry, didn't know that captured videos from TV goes for this too. It does not - But you used the phrase "collected from the internet", which does!


Cheers

[KpeX]

This is a borderline case, and if you do a search on TV caps or music videos you'll see there's no definitive clarification of the forum rules on this point.

Getting back to the original question, MP2 and AC3 are both lossy compression formats, and converting to either will cause a loss in quality. AC3 has the advantage of the possibility of 5.1 and more compliancy in NTSC-land. MP2 has the advantage of higher-quality free encoders available.

[dea]

KpeX: okey, thanks for the clarification.
I have to go with AC3, hence a NTSC dvd.
But it's good to know in other cases anyhow!
A follow-up question, if you have time; I know that AC3 and MP2 is lossy, but comparing to the original captured file - is there any noticable diffrente?
The thing that I'm confused of is that I first retain a MP2 file from the de-mux, and then I have to "re-encode" it to get the AC3 file. Dosen't that make the AC3 file a more lossy compression then the MP2 that I obtain the AC3 from? Or is it not a "real" encoding process so to speak?

Thank you

/Andreas

[daphy]

in principle:
reencoding out of lossy format into another lossy format means always increasing loss
If you want to stay compatible for NTSC-land, maybe a uncompressed PCM out of your MP2 will be a solution.

Advantage:
no compromises in sound quality

Disadvantage: ~2h sound -> ~200MB AC3/MP2 (depending on bitrate, channel amount etc.) -> ~1400MB 2 channel PCM
best solution if you got a dual layer DVD writer ;)

[dea]

But a uncompressed PCM sound out of the MP2 file must mean that I get the PCM from an already comprssed file, hence the PCM won't be any better then the MP2 itself. Or am I totally out here? Dosen't make much sense to me though.

If the PCM sound in fact IS better of in quality compared to the original MP2 file (taken from an MPG or AVI video file), this would be great!
Due to that I've runned into slight problems encoding the AC3 sound in DolbyD. Soft Encode starts out just fine, but after 2-3 minutes or so in the audio file, the whole program just shut down. Tried this a couple of times and also checked the AC3 in AC3Fix, but camed out clean. Maybe you know what's wrong?


/Andreas

[daphy]

:D old bug,
1. uninstall softencode
2. delete ALL depending registry keys (you will find them in only one folder of the registry - use search function of regedit.exe)
3. install again
and of course
4. give feedback

PCM out of MP2 surely can´t be better than the original quality of MP2

BUT is NTSC DVD compatible - MP2 NOT

that´s the point my friend inside NTSC land, as you called it ;)

[dea]

Yey! Thanks Daphy.
Softencode works sweet now. And I've runned my new PCM file thru it to get an DolbyD AC3.

One question though - is there any purpose to encode it as an 3/2, since it's from the beginning a stereo 2/0 sound? Isn't the surroundspeakers or satellitespeakers also active in ordernary stereo sound on a normal system?
Shall I use the "Dolby surround encoded" option that is highlighted when I choose 2/0? Is this just crap? Any point using it if it's mostly just music, going to be played on a surroundsystem?

And one quicky if your up to it. Haven't got the hang of the LFE. What does it do? Been searching for the answer in some threads, but with no result. I think it has something to do with the subwoofer... ? or am I totally wrong here?

Cheers!

/Andreas