DVDA-2 AC3 How to stop AC3 Recompress

gbohn wrote on 6/2/2004, 7:47 PM
O.k., so here I am trying out the DVDA-2 demo, and I had a few AC-3 related problems. Maybe someone can tell me if these are 'demo' related problems, or if the full program has the same limitations (Or if I just haven't figured out how to accomplish my task).

I added an .MPG media file from my Panasonic DMR-E80 DVD-Recorder. This is a combined NTSC 704x480 video with 'stereo' AC-3 audio. I have project video set to 704x480 and Project audio set to 'AC-3'.

I noticed that:

1) "Optimize DVD' says that the Video of the media file will not be changed
('Green Check'), but that the audio will be recompressed ('Yellow
diamond').

How can I prevent it from degrading the audio? (since it wants to
decode the AC-3 audio only to reencode it back to AC-3?)

All the 'Audio 1' settings are grayed out except ' Recompress settings',
and all the available settings make no difference as far as the yellow
diamond goes (PCM, AC-3, or AC-3 5.1).

2) I noticed that performing a preview of this clip shows the video, but I
don't hear any audio. (Using an MPEG with, say Mpeg Layer 2 audio
seems to preview the audio O.k.).

Are these 'features' related to the Demo, or would the Full product have these same problems?

I also have to say I'm disappointed that they seems to have changed the interface enough that some simple operations are less intuitive, and more time consuming than they used to be...

Thanks in advance;

-Greg Bohn

Comments

mike_2004z wrote on 6/3/2004, 7:44 AM
Hi,

I can't help you regarding your AC-3 audio problem but was it OK with DVDA version 1 (no re-compression)? Perhaps your AC-3 audio is in stereo and your project setting is for 5.1 ?

Yes, I do agree with you that DVDA-2 is user un-friendly at best. Everything is squeezed in on one screen (especially that Property tree/panel on the right - I hate that selection menu) and it take quite a long time to find an option even after you familiar with the thing. It would be much better if SONY split that menu and put them on separate tabs (ex: Menu Property Tab, Button/Object Property Tab, Color Sets Tab, Global Setting Tab).
rontvs wrote on 6/3/2004, 12:43 PM
I think it's because your MPEG2 file contains the AC3 audio (multiplexed) insted of a seperate AC3 audio file. I have tried this with some of my files and it ONLY brings in the Video stream. I HOPE this can and will be fixed.

Ron
gbohn wrote on 6/3/2004, 5:00 PM
> can't help you regarding your AC-3 audio problem but was it OK with
> DVDA version 1 (no re-compression)?

DVDA-1 either doesn't see or doesn't use the AC-3 audio at all (Both the preview and a created disk are soundless).

I was hoping that since DVDA-2 now supports a project setting of 704x480, etc, it would be better. (Heck, even TmpGenC DVD Author can pass AC-3 through without re-encoding it).

Since Sony (in it's wisdom) has decided to not allow you to create disks, or work with AC-3 in the DVDA-2 demo, I am unable to tell if this is the same old deficiency, or just something specific to the Demo.

Since the demo mentions that it doesn't support AC-3, I can't tell if it's just the preview that would be silent, or the created DVD as well (just like in DVDA-1).

Heaven forbid if I should be able to tell if the program would actually work or not by actually creating something with it...

>Perhaps your AC-3 audio is in stereo and your project setting is for 5.1 ?

Nope, I have tried the settings at AC-3 stereo and AC-3 5.1 with the same results.

I'm guessing the output from the DMR-E80 has a different bitrate (or some other setting) that the 'secret' internal settings are set to. Either that, or it just doesn't see the audio at all.

Would be nice if these settings were configurable to match your desired source material. But, I guess they figured no one would ever possibly want to use material not created with Vegas...

Heck, I'm not bitter... :-)

-Greg Bohn
gbohn wrote on 6/5/2004, 10:28 AM
Yep, after further 'fiddling' with it, it seems that DVDA-2 just fails to notice the accompanying audio information.

When I ran a utility to de-mux the original file, put the '.mpa' audio file in the same directory as the original .MPG, and then added the MPG, I was able to preview the audio. (I can only hope they would stay synchronized).

It's not obvious why it can find multiplexed MPEG Layer 2 audio in an .MPG file, but can't deal with multiplexed AC-3.

Things like this don't seem to fit with the 'professional quality' billing...

-Greg Bohn
mike_2004z wrote on 6/5/2004, 9:54 PM

Hi,

I do sometimes wish that DVDA-2 would allow the user more control over the final encoding process. Mpeg-Layer 2 audio is a valid DVD spec outside of North American and I really don't understand why DVDA-2 must convert it to AC-3. It would be nice (not really 'nice' but a 'MUST') to have an option that allow the user to have more control and choose whether to encode the audio or not. Let the user make the decision; not the program, especially when it make a wrong decision.

If DVDA-2 'really smart' then it's not THAT HARD to determine of which region the input video is intended for. Ok, here is a hint for DVDA-2 programmers, based on the resolution of the input video, you know right away if the video for PAL or NTSC and give the user the appropriate option - leave the audio alone or force encode it to AC-3 (or give a simple message box warning and let the user make the decision).

Ok, here is another free 'hint' on how to determine the correct DVD size:

- Know the bitrate of the input video (CBR/VBR). Calculate the size of video ONLY (based on the lenght of the video). Or do a internal de-mutiflex of the video and get the size (do it while builting the peak of the audio so it would be transparent from the user point of view).

- Know the bitrate of the input audio (already from your determine audio peak routine - see above). If convert to AC3- then calculate the total size based on the bitrate of DVDA-2 default bitrate of AC3 encoding routine. If not need to convert to AC-3 then get the size of the MpegLayer 2 audio file size only (if not need to convert to AC-3 -> it's a PAL audio standard - give the user option).

- Calculate the size of all the menu(s) and whatever space need for DVDA-2 to create final output DVD.

- Total all these up and give a pretty close estimate of the final DVD size.

- If over then give some warning and give choice of re-encoder video/audio whaterver to make it fit. If user force over-ride then leave the size alone and user need to do what ever to make the final DVD to fit - Shrink it).