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Old 26th June 2008, 01:31   #1  |  Link
nitricpyro
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mp3 vs. ac3

I have been using the program Gordian Knot to create DivX files for use on my media pc. I have typically converted the ac3 sound files into 320 / kbps mp3 files.

Could this be responsible for a significant portion of my DivX files having AV sync errors, up to a few seconds in some.

Is it better to "just mux" the ac3 audio?

Thanks for all your help!
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Old 27th June 2008, 01:16   #2  |  Link
fibbingbear
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I am not an expert with DivX so I can't tell you a definitive answer. I know that when I use DGIndex it sometimes encodes a delay in the AC3's filename. You should make sure that the delay associated with the AC3 is offsetting the MP3. In other words, just ripping the AC3, converting, and muxing WITHOUT setting the appropriate offset can screw things up.

On a second note, in my limited experience with DVD ripping, most AC3 I've run across is in the range of 192kbps to 224kbps. Why would you want to encode an MP3 version of it at 320KBPS? It'll be larger and lower quality (of course, at 320kbps, I doubt you'd be able to tell the difference, but still).

So in conclusion, try muxing with the AC3. If it solves the offset problem, then you've got two birds with one stone
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Old 27th June 2008, 02:06   #3  |  Link
nitricpyro
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Quote:
Originally Posted by fibbingbear View Post
...AC3 I've run across is in the range of 192kbps to 224kbps...


Not exactly what I was looking for in an answer, however this is very enlightening! I for some reason assumed the ac3 audio to be of wave quality and was trying to get the best possible sound. Since I was wrong though, I will start using ac3 either way!

Thanks
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Old 2nd July 2008, 13:47   #4  |  Link
looney
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Quote:
Originally Posted by nitricpyro View Post
I have been using the program Gordian Knot to create DivX files for use on my media pc. I have typically converted the ac3 sound files into 320 / kbps mp3 files.

Could this be responsible for a significant portion of my DivX files having AV sync errors, up to a few seconds in some.

Is it better to "just mux" the ac3 audio?

Thanks for all your help!
I dunno if you doing transcoding in vdub or similiar tool with 44.1 forced output. In the old days forcing 48kHz->44.1kHz in vdub (well vdubmod support ac3) could result in audio delay which in most cases worsen to the end and audio in log files could end up 20min or more before the video. So it could be forced resampling that caused that.
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