Audio format confusion

yirm wrote on 3/10/2003, 10:21 PM
I'm really confused about audio formats. It seems that DVDA supports two formats -- PCM and AC3. Does this mean that the MPEG audio that that can be included in the MPEG files exported using the MainConcept plugin cannot be used used in DVDA. If you import the audio stream included in a MainConcept MPEG2 file in DVDA, it has to be then converted to PCM or recompressed to AC3, resulting in further sound quality loss? If you have the audio stream in your MPEG file, does it count against the calculated size of your DVD even if you use a separate WAV or AC3 file?

Thanks.

-Jeremy

Comments

Control_Z wrote on 3/10/2003, 10:29 PM
Good questions. Let me add: Why does DVDA always want to rerender my audio? Why can't I just render the needed format from Vegas? Or can I?
SonySDB wrote on 3/11/2003, 9:11 AM
Yes. MPEG audio exported from the MainConcept plugin will be converted to PCM or AC-3.

The audio stream in your MPEG file (even if you use a separate WAV or AC-3 file) may inflate the calculated size of your DVD slightly depending on several factors.
SonySDB wrote on 3/11/2003, 9:13 AM
In Vegas, you need to render your audio a WAV file (48 kHz, 16 bit, stereo, PCM) or AC-3 to avoid rerender in DVD-A.
yirm wrote on 3/11/2003, 9:33 AM
This is disappointing. I would have expected that the MPEG audio could be used in DVDA. There are times when the sound quality might be acceptible, but you need that last bit of space. It seems really odd that DVDA doesn't accept the MPEG2 files as is which are created from Vegas!

-Jeremy
jetdv wrote on 3/11/2003, 10:48 AM
Why is it disappointing? What's wrong with AC-3 audio?
yirm wrote on 3/11/2003, 11:46 AM
There's nothing wrong with it at all. But it is 5 or 10 times the size as the MPEG audio stream in the MainConcept MPEG2 video. I don't remember the exact sizes, but it is substantially larger. I'll check it out when I get home and post the filesize comparisons.

-Jeremy
bcbarnes wrote on 3/11/2003, 2:03 PM
Don't forget that MPEG audio is not in the NTSC DVD spec. Although most players seem to be able to play it, the NTSC DVD spec allows only AC-3 and PCM.
Baylo wrote on 3/11/2003, 2:09 PM
True, but I think MPEG audio IS in the PAL DVD spec (in addition to DD and PCM), so it's not an unreasonable request.

Mark
bcbarnes wrote on 3/12/2003, 10:16 AM
Mark,

Quite right. I sometimes forget that we live in a pretty large world and not everyone uses NTSC video...
Aje wrote on 3/12/2003, 4:03 PM
I maybe doing wrong but my VV4 rendered AC3 files always need rerendering in DVDA
when preparing !
Aje
jopereira wrote on 3/13/2003, 7:25 AM
"But it is 5 or 10 times the size as the MPEG audio stream in the MainConcept MPEG2 video"

Just a note: AC-3 2-channel @ 192Kbps already has the best audio quality you can squeeze in AC-3. But to be honest I don't know the frequency responce of a 192Kbps MPEG audio stream.