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Old 14th December 2005, 02:43   #1  |  Link
jweathers7
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Remove or prevent delays during AC3 Encoding?

I am in the process of inserting some deleted scenes back into Attack of the Clones. I have successfully edited the video, but I am having some trouble with the audio portion.

Specifically, I have ripped the soundtrack and the deleted scene soundtracks into AC3 files. I then used BeSplit to split up the soundtrack into chunks including small neighborhoods around areas where I need to create sound transisitions. I then decoded these neighborhoods into groups of 6 Mono WAVs.

After making my transitions successfully, I then reencode the neighborhoods that I had previously decoded with the intention of then joining everything back together into one big AC3. This way the loss of quality from reencoding is limited to small 2 - 4 second windows around the transitions.

Unfortunately, Softencode seems to add a small bit of silence at the beginning of each AC3 that it produces. While the silence is really small and unnoticeable if you just play it in isolation, it is very noticeable when joined back into the soundtrack.

Is there some way to eliminate these delays using Softencode or another encoder? The BeSweet encoder seems to barely add any delay if at all, but it has the problem that the volume seems to be cut in half and the sound wave seems inverted as well.

I would rather not reencode the entire soundtrack as I am trying to preserve as much quality as possible. However, even when I tried doing this, I noticed that BeSweet complained about overflow issues when trying to decode the entire soundtrack which doesn't look good...

Any help or advice would be greatly appreciated!
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Old 14th December 2005, 14:29   #2  |  Link
XIII
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Hi

You should be able to encode your waves to ac3 using besweet,
the way I do it is create a list.mux then load
that into besweet using BeSweetGUI v0.7 b4

I have a test file you can try all you need to do is drop
it straight on C drive and open the mux file with besweet,
the ac3 file created is a channel test for each speaker so you
Know the order is right.

Then all your need to do is edit the paths in the mux file
with note pad for your waves when you want to encode them.

You can get the file here

http://www.savefile.com/files.php?fid=2231546


XIII

Last edited by XIII; 14th December 2005 at 14:41.
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Old 15th December 2005, 03:18   #3  |  Link
jweathers7
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Quote:
Originally Posted by XIII
You should be able to encode your waves to ac3 using besweet,
the way I do it is create a list.mux then load
that into besweet using BeSweetGUI v0.7 b4
Thanks for the suggestion, but I have no problem encoding with BeSweet. I have done it easily using a mux file just as you describe.

The problem with this approach however is that when I examine the AC3 files created by BeSweet by decoding them into WAV files, it becomes apparent that BeSweet's encoder (ac3enc) not only cuts the volume nearly in half, but strangely it seems to invert the WAV. The first issue seems to be a known problem with no fix in sight. The second is just bizarre.

Thus, ac3enc seems unacceptable unless I can get around these two issues.

That is why I was using Softencode. However, it introduces these delays at the beginning. That is why my question is whether it is possible to remove or prevent these delays. It doesn't look like there is option that could effect this in Softencode, but I wanted to make sure or see if people have found alternative ways of dealing with this issue.
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Old 15th December 2005, 14:45   #4  |  Link
XIII
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Hi

Volume is easily solved by using the Boost in besweet.

I added the link to the file because you said the wav
file gets inverted which it doesn't do when I use that
mux file in that order.

If you can get your hands on "Sony Vegas+DVD Architect"
you can use that to encode your wav files to ac3.

Other than that there are loads of programs to add or remove
a silence from the beginning of an ac3 file.


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Old 15th December 2005, 17:57   #5  |  Link
jweathers7
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Quote:
Originally Posted by XIII
Volume is easily solved by using the Boost in besweet.
Hmmm. I'll try that although it might be hard to fine tune it so it boosts the sound back to the original volume with enough precision so that the transition is not noticeable. It's definitely worth a shot though! Is there a way to measure the difference in dB between two WAVs to see how much Boost I need to apply?

Quote:
Originally Posted by XIII
I added the link to the file because you said the wav
file gets inverted which it doesn't do when I use that
mux file in that order.
Ah. Now, I see. I'll give it a try when I get back home. (I am currently away on a nice ski vacation.) However, I wonder if we are talking about the same thing when we say "inversion". I do not mean channels inverted if that is what you mean. Rather, I mean that when I normalize say the original Center channel WAV and compare with a normalized version of the Center channel WAV decoded from the final AC3 file, the new version is the inverse wave of the original disregarding error introduced by the coding/decoding process.

Quote:
Originally Posted by XIII
Other than that there are loads of programs to add or remove
a silence from the beginning of an ac3 file.
Can you name a few in particular? Thanks!
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Old 15th December 2005, 19:13   #6  |  Link
tebasuna51
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In my test with SoftEncode the delay is only 5.333 ms.
I try to add 26.667 ms at the beginning of wav, an after cut the first 32 ms frame (with DelayCut, or with WinHex), the sync is recovered but still remain this time (about 5 ms) until the wav reaches the 100% volume, and can produce audible click.

The same results with Headac3he (+6Db). With BeSweet same delay, half volume and inverted wav.
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Old 16th December 2005, 16:21   #7  |  Link
XIII
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Hi

The only real way to get the right dB when using boost is
to have a small audio clip of the source wav's say a minute
long and test it, takes a few seconds at most.

Besweet its self allows you to add or remove a silence,
or there's a small app called " AC3 Delay Corrector "
DVD lab pro can also do this.

Strange I have used many methods to encode from wav to
ac3 and have never had any of the above.

I will say though Softencode was by far the worst.


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