Please explain

JohnI wrote on 3/14/2003, 4:10 PM
Can some-one please explain the benefits of using the DVDA Video only render output from VV4 before importing in to DVDA? It seems that a regular DVD compatible single file render of audio and video can be imported in to DVDA without re-compression. So why would I go to the trouble of the DVDA render which seems just to create unecessary work?

Thanks JohnI

Comments

teknal wrote on 3/14/2003, 5:56 PM
I might be wrong because I haven't read the manual yet but I think DVDA only authors using AC3 audio and the video+audio render (like DVD NTSC setting) encodes uses layer 2 audio, not ac3). So by rendering using the DVD Architect stream you'd probably save some render time and then render a separate AC3 audio stream and bring the two together in DVDA. That's my take on it from using it so far. I've got to read the manual one of these days!

bcbarnes wrote on 3/14/2003, 6:09 PM
JohnI,

If you want to use MPG audio on your DVD, then you are absolutely correct - a single MPG file with audio and video would work great. Keep in mind, however, that MPG audio is NOT in the DVD spec in the NTSC world (but it is in the PAL world...) so you would be creating a DVD that does not meet the spec - although most players would be able to play it. DVDA would probably want to re-encode this into AC3 or PCM, and so you'd have that additional step, but at least it would meet the DVD specs.

Creating an MPG file with the video only and a separate AC3 file for the audio allows you to have a smaller MPG file (since there is no audio data in it), and to meet the DVD spec for audio. In addition, hopefully someday we'll be able to have multiple audio files for each video, allowing multiple languages, director commentary, etc..

JohnI wrote on 3/15/2003, 5:36 AM
Thanks for the feedback and from the comments let me try to summarise:
1) Firstly I am in the 625 world and make 625 DVD so if the feedback is correct, mpeg audio is legal and in fact the standard for 625 DVDs.
2) However DVDA forces me to use AC3 or uncompressed which is not 625 friendly!!
3) If I create a compliant stream with mpeg audio it forces a recompress to AC3 with loss of quality! and not 625 specs!!
4)Conclusion if I want to continue to use DVDA my best choice is Uncompressed PCM which will bring quality benefits, no recompress and playability on all players.
Correct?? John I
SonyEPM wrote on 3/17/2003, 8:40 AM
PAL users (who may need to avoid AC-3 for compliance reasons) should:

1) Render PCM audio from their Vegas projects, and render PAL MPEG from their Vegas projects. Render separate files, same base name, same length, to same folder.

2) Link the two together in DVDA (DVDA will auto-link these, or you can do it manually).

Follow 1 & 2 and you will have high quality, no-recompress a/v.

3) Ideally you don't convert the audio to PCM (or AC-3) after it has been encodied once as MPEG audio- that will result in a quality loss.

MarkWWWW wrote on 3/17/2003, 11:05 AM
I don't think there should be any problem with using AC-3 audio on PAL/625 DVDs.

Although the original DVD standard for PAL/625 specfied either PCM or MPEG audio, the standard was changed to allow AC-3 audio instead of MPEG audio.

Here's a quick quote from the DVD FAQ at DVD Demystified, talking about audio on PAL/625 DVDs:

"The original spec required either MPEG audio or PCM on 625/50 discs. There was a brief scuffle led by Philips when early discs came out with only two-channel MPEG and multichannel Dolby Digital, but the DVD Forum clarified in May 1997 that only stereo MPEG audio was mandatory for 625/50 discs. In December 1997 the lack of MPEG-2 encoders (and decoders) was a big enough problem that the spec was revised to allow Dolby Digital audio tracks to be used on 625/50 discs without MPEG audio tracks."