Problem with AC-3 encoding

PossibilityX wrote on 7/21/2004, 1:18 PM
I rendered the audio from my film as an AC-3, as follows:

192Kbps, 48k stereo, dialog normalization at -31dB, dynamic range compression set to “NONE” in both line mode profile and RF mode profile.

On test renders of smaller clips, this setting yielded a good waveform in DVDA 2, so I applied the settings to a 65 minute project consisting of 23 audio tracks, mostly spoken word but also containing some music. (No more than two tracks play at the same time, however----it’s not a constant 23 tracks stacked atop one another, all the way through.) The render took almost 7 hours, which I guess isn’t surprising given the number of tracks and the length of the project.

My problem: the rendered AC-3 clip is completely silent and shows no waveform at all in DVDA 2. Was there something wrong with the settings I used, or the number of audio tracks in the project, or something else? Admittedly my earlier tests were on short clips consisting of just a few audio tracks.

What settings would you guys use, given the total length of the project to go to DVD (90 minutes total)?

Any help is appreciated.

Comments

JJKizak wrote on 7/21/2004, 2:07 PM
A 7 hr render for just AC-3 sounds a bit much, almost like you were rendering video and AC-3 together. My multitrack (about 15) AC-3 -5.1 rendered in about 20 minutes or less for about a 59 minute length. Ac-3 in Vegas must be rendered by itself as the Video also, then they are recombined in DVD-A2 automatically.

JJK
PossibilityX wrote on 7/21/2004, 2:30 PM
JJ, do you mean the video portion must be rendered first, then the audio?

I rendered the audio first as an AC-3, then the video as an MPEG-2, DVDA NTSC stream. Video also took about 6.5 hours, but this doesn't surprise me given the number of transitions and FX.

But almost 7 hours for the audio did surprise me quite a bit.
LightMfg wrote on 7/21/2004, 4:29 PM
Did you tell DVDA to use your Ac3 file in the audio link properties box for the associated item ? DVDA will assume that you want to use the audio track on the video file unless you tell it otherwise
JJKizak wrote on 7/21/2004, 4:34 PM
The order doesn't matter as long as you render each separately and name each file the same with the exception of the file ending. Also in DVDA2 make sure in the options that the "combine like files" (I forgot the exact nomenclature) is checked so the AC-3 file will automatically combine with the mpg file. Just for laughs try a short one again maybe about 5 minutes to make sure it works.

JJK
PossibilityX wrote on 7/21/2004, 4:49 PM
The problem seems to have solved itself somehow.

After another test of a 6-minute clip which only took a minute to render, I (re)rendered the 65 minutes of audio using the same settings, and this time it only took 11 minutes. Go figure. Dropped it into DVDA and got a nice waveform and sound.

Who knows why? It’s mysterious. But I’m glad it fixed itself.

Thanks to everyone for the tips and suggestions; it is much appreciated.
smhontz wrote on 7/21/2004, 5:06 PM
I've had this problem myself. Sometimes the AC3 encoding goes bonkers and just CRAWLS. Usually if I kill it, and select the whole project (to create a loop region) and then say "render loop region", it will work. Sometimes moving something around helps.
johnmeyer wrote on 7/21/2004, 8:17 PM
I am sorry to hear that this problem still exists in the current release of Vegas. I have had this problem since the original release of Vegas 4. The only solution is to re-start Vegas and then start the render again.