AC3 re-encoding quality

[SpEeDaMiGo]

Hi

I've got a 2h movie with an AC3 Audiotrack (DolbyDigital 5.1), which is encoded at an average of ~448kbps (~390mb). I'd like to make the rip with ac3 5.1 available but the original file is too big for me. What bitrate for re-encoding (using the guide of Doom9) would you recommend me ?
What bitrate to get equal quality of mp3 ~160kbps (stereo)?

Thanks

[SpEeDaMiGo]

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Come on guys ..... don't tell me I'm the only one encoding AC3 tracks.

[MaTTeR]

Originally posted by SpEeDaMiGo
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Come on guys ..... don't tell me I'm the only one encoding AC3 tracks.

Actually you might be :)

Can't help you as I usually keep the AC3 as is and then mux it.

[vac]

some time ago, i had the same problem. I tried to downsample ac3 stream from 448kbit to 384kbit or 192kbit. The only program i found was Soft Encode (from Sonic Foundry). This program can open 5.1 ac3, it can even create it (!) and it can also downsample it. But it takes a looong time, and you need A LOT of free hdd space. It temporaly creates some uncompressed pcm/wavs (5.1 creates 6 wavs), so for 2 hours ac3 stream you need approx 9 Gigabytes of free hdd space (6 x 1500=9000), and the opening/decoding is very slow ...

then you can downsample to lower frequency.

maybe i was doing some mistakes, BECAUSE the quality was quite poor :-((

downsampled ac3 from 448 to 384 was acceptable (but still i was recognizing the differencies) but to 192 it sound really awfull :-(((

but maybe i was doing something wrong...

[Sherlock Holmes]

Hi guys
I know what you should do. :)
1 - Run SonicFoundrySoftEncode.
2 - Open the AC3 file.
3 - Decode it to a WAV in WindowsPCM format.
4 - Seperate that WAV to 6 WAV.
5 - Import those 6 WAVs to SonicFoundry
6 - Go and set your settings in SonicFoundry like lowing the bitrate.
7 - Make the AC3

I tested this , and the result was very very good.

I know it takes a lot of time and also a lot of hard disk space. But the result is nice.

:D

[DSPguru]

today i will be releasing BeSweet v0.9. it can automaticly create 6 mono wavs of 44.1khz from AC3/VOB input.