AC3 problem at DVinfo.net

Denis Basic · March 4th, 2003, 04:24 PM

Hi folks,

I am wondering if there is an easy solution for my following problem. Namely, an AC3 file, which I produced using FCP, Peak DV 3.0, and APack, when played in the preview of the DVD Studio Pro 1.5.2, “breathes”, i.e. the volume goes up and down by itself. The file is fairly long, about one hour of program. What am I doing wrong? Would the sound be better if I burn the DVD? My experience tells me that sometimes those previews in DVDSP are not accurate. Any help?

Here is the procedure, which I followed to create the AC3 file:

1. I created the AIFF file by using FCP (Export>QuickTime>MPEG2+AIFF);

2. I used Peak DV 3.0 to create two separate tracks of the AIFF file (File>Export Dual mono). /I am confused why this is not dual stereo? Where is dual stereo option?/

3. Having done so I incorporated the two tracks into APack and created the AC3 file.

The size of the resulting audio AC3 file was significantly smaller than the one of the original AIFF file that was my goal. Besides, I read that AC3 audio was much more compatible with a larger number of DVD players.

In any case, the AC3 file I produced is useless. Any ideas of how to fix this problem?

In advance thanks a lot for your advice.

Denis

Jeff Donald · March 5th, 2003, 11:00 PM

This is due to dialog normalization (DN) and the dynamic range compression (DNC) settings (profile) you have selected.

This is in may reference material from some of the lists and forums I subscribe to and visit. I do not know the source.

Quote:

DN and DNC are intimately related. DNC profiles are hard wired into the
decoder, with a null band that scales roughly -31 to -21 dB (Standard
compression profiles) or -41 to -21 dB (light compression profiles).
Decoders use the DN to lower the volume of the AC-3 stream so it sits within
the DRC profile's null band, where no compression is applied. If you set
your DN wrong (ie, -27, or -31) the result is going to be gain pumping and
other unwanted changes in volume.

The only way around this is to set the DNC to None, which works in most
situations, or do everything correct and find your DN. Encoding your AC-3
file with the correct DN solves ALL problems. This is the key that unlocks
AC-3.

To find your DN, open the audio file in Peak DV 3 (or Pro Tools free, or
Finl Cut Pro) and play a section of just dialog. Look at the level meter,
and try to determine the average volume of the dialog. Key that number into
A.Pack's dialog normalization text box. A hack, to be sure, but it works
well once you figure out how to spot the average dialog level.

Jeff

Curtis T. Stoeber · May 27th, 2003, 04:35 PM

So setting the DNC to "None" will negate the need to mess with the Dialog Normilization?

I get the pumping effects (music quiets down when an explosion occurs, etc etc etc) if I play my 6 track AC3 files that I created through the stereo outputs of a DVD player or on the computer itself. When I play it on a real 5.1 audio system, there is no pumping. Setting the DNC to "none" seems to eliminate the pumping when it folds down to stereo, so I have been doing that. But I have never touched the DN. I just want to make sure that I don't also need to worry about the DN settings.

PS - Dual mono is just that... the same audio track played through both the left and right channels, instead of 1 mono audio track played through only the center.

Jeff Donald · May 27th, 2003, 04:50 PM

Quote:

So setting the DNC to "None" will negate the need to mess with the Dialog Normilization?

Yes, to get the pumping to stop set DNC to none. You can leave the DN settings alone, unless you want to follow the second part and try to use the normalization.

Curtis T. Stoeber · May 28th, 2003, 02:02 AM

Sounds like a winning solution to me. I'd rather just mix it right to begin with than try to mess with the normilization "feature". So far it has worked for me. Good to know.

Linc Kesler · May 28th, 2003, 10:18 PM

I have run into another problem with APack. In fact, it's the apparently dreaded OS 1 error message problem that seems to abort every attempt to compress AIFF files to AC3. Evidently this is a common problem that seems worse under the 10.2.3 and up updates. I've tried all of the fixes I found on the Apple discussion lists, except running APack under OS9, which I will try tomorrow , if my machine permits it, being one close to the last hardware update that no longer supports OS 9 (the other suggested options involved running it in terminal from the unix command line, and running the file through quicktime, neither of which worked). Sooo, my question is whether any other compression options for audio are commonly available, or is uncompressed AIFF the only practical alternative?

Thanks in advance for any advice. Even with the many learning curve frustrations, I have to say I'm enjoying myself, though those impending deadlines are beginning to really scare me.

Linc Kesler

Curtis T. Stoeber · May 29th, 2003, 01:17 AM

For what it's worth, I have NEVER EVER been able to get A.Pack to work in OS X. This will probably (hopefully) change with the new DVD Studio Pro 2 update. It works flawlessly in OS 9. I have to assume that others can get it to work somehow in X, though. Otherwise I think we'd hear a bit more on the subject.

Linc Kesler · May 29th, 2003, 06:20 PM

Just an update: A.Pack did work flawlessly for me on OS9, and at a much faster speed as well, so for those of us who can boot to OS9, this does look like a good solution.

Linc Kesler

Richard DuPree · May 30th, 2003, 09:55 AM

The OSX project I am working on has necessitated multiple AC-3 encodings of the audio tracks as the project is refined and finalized. Of the six or so passes through APack, two have spontaneously aborted. I have simply re-started the encoding, and each time it has gone successfully to completion. I notice no difference in processing time between the OSX and OS9 versions. BTW, I'm using OS 10.2.6.

March 4th, 2003, 04:24 PM	#1
Denis Basic Regular Crew Join Date: Jul 2002 Location: Seattle, WA USA Posts: 35	AC3 problem Hi folks, I am wondering if there is an easy solution for my following problem. Namely, an AC3 file, which I produced using FCP, Peak DV 3.0, and APack, when played in the preview of the DVD Studio Pro 1.5.2, “breathes”, i.e. the volume goes up and down by itself. The file is fairly long, about one hour of program. What am I doing wrong? Would the sound be better if I burn the DVD? My experience tells me that sometimes those previews in DVDSP are not accurate. Any help? Here is the procedure, which I followed to create the AC3 file: 1. I created the AIFF file by using FCP (Export>QuickTime>MPEG2+AIFF); 2. I used Peak DV 3.0 to create two separate tracks of the AIFF file (File>Export Dual mono). /I am confused why this is not dual stereo? Where is dual stereo option?/ 3. Having done so I incorporated the two tracks into APack and created the AC3 file. The size of the resulting audio AC3 file was significantly smaller than the one of the original AIFF file that was my goal. Besides, I read that AC3 audio was much more compatible with a larger number of DVD players. In any case, the AC3 file I produced is useless. Any ideas of how to fix this problem? In advance thanks a lot for your advice. Denis __________________ Denis Basic

May 27th, 2003, 04:35 PM	#3
Curtis T. Stoeber Join Date: Dec 2002 Location: Lakewood Colorado USA Posts: 150	So setting the DNC to "None" will negate the need to mess with the Dialog Normilization? I get the pumping effects (music quiets down when an explosion occurs, etc etc etc) if I play my 6 track AC3 files that I created through the stereo outputs of a DVD player or on the computer itself. When I play it on a real 5.1 audio system, there is no pumping. Setting the DNC to "none" seems to eliminate the pumping when it folds down to stereo, so I have been doing that. But I have never touched the DN. I just want to make sure that I don't also need to worry about the DN settings. PS - Dual mono is just that... the same audio track played through both the left and right channels, instead of 1 mono audio track played through only the center.

May 28th, 2003, 02:02 AM	#5
Curtis T. Stoeber Join Date: Dec 2002 Location: Lakewood Colorado USA Posts: 150	Sounds like a winning solution to me. I'd rather just mix it right to begin with than try to mess with the normilization "feature". So far it has worked for me. Good to know.

May 28th, 2003, 10:18 PM	#6
Linc Kesler Regular Crew Join Date: Aug 2002 Location: Vancouver BC Posts: 65	I have run into another problem with APack. In fact, it's the apparently dreaded OS 1 error message problem that seems to abort every attempt to compress AIFF files to AC3. Evidently this is a common problem that seems worse under the 10.2.3 and up updates. I've tried all of the fixes I found on the Apple discussion lists, except running APack under OS9, which I will try tomorrow , if my machine permits it, being one close to the last hardware update that no longer supports OS 9 (the other suggested options involved running it in terminal from the unix command line, and running the file through quicktime, neither of which worked). Sooo, my question is whether any other compression options for audio are commonly available, or is uncompressed AIFF the only practical alternative? Thanks in advance for any advice. Even with the many learning curve frustrations, I have to say I'm enjoying myself, though those impending deadlines are beginning to really scare me. Linc Kesler

May 29th, 2003, 01:17 AM	#7
Curtis T. Stoeber Join Date: Dec 2002 Location: Lakewood Colorado USA Posts: 150	For what it's worth, I have NEVER EVER been able to get A.Pack to work in OS X. This will probably (hopefully) change with the new DVD Studio Pro 2 update. It works flawlessly in OS 9. I have to assume that others can get it to work somehow in X, though. Otherwise I think we'd hear a bit more on the subject.

May 29th, 2003, 06:20 PM	#8
Linc Kesler Regular Crew Join Date: Aug 2002 Location: Vancouver BC Posts: 65	Just an update: A.Pack did work flawlessly for me on OS9, and at a much faster speed as well, so for those of us who can boot to OS9, this does look like a good solution. Linc Kesler

May 30th, 2003, 09:55 AM	#9
Richard DuPree Regular Crew Join Date: Oct 2001 Location: Denton, TX Posts: 38	The OSX project I am working on has necessitated multiple AC-3 encodings of the audio tracks as the project is refined and finalized. Of the six or so passes through APack, two have spontaneously aborted. I have simply re-started the encoding, and each time it has gone successfully to completion. I notice no difference in processing time between the OSX and OS9 versions. BTW, I'm using OS 10.2.6.