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View Full Version : Best way for dolby surround downmixing?

ChAoS Overlord
24th March 2002, 10:24
What AC3 decoding program should I use? Do I have to enable dolby surround downmix in dvd2avi allready or only later on in the decoding program? What MP3 encoding settings should I use? Is it better to have an AC3 2 channel dolby surround than to reëncode to mp3? If so, is it possible to reëncode a 5.1 channel AC3 to 2 channel Dolby surround AC3?

Thx in advance for the nfo.
DSPguru
24th March 2002, 10:38
how about reading the guides (http://doom9.org/ac3tomp3.htm) ?
ChAoS Overlord
24th March 2002, 15:18
There really isn't much info about dolby surround downmixing in it...
DJ Bobo
24th March 2002, 15:49
AC3 decoding program: AZID
Typical command line: azid -c normal audio.ac3 audio.wav
That makes automatically WAV in Dolby Surround.

You can encode that WAV to MP3 or AC3 as you want.

There is no specific MP3 settings, but you may choose STEREO instead of JOINT STEREO for 100% accurate Dolby Surround encoding.

If you have AC3 2.0, you can keep it if you're not worring too much about the bitrate. That garantees highest quality.

If you have AC3 5.1 and want Dolby Surround output, as said you make WAV with Azid, then encode it to mp3 or ac3.

You may go for 2.0 192kbps AC3 if the bitrate is not a problem. You may select "Dolby Surround encoded" for accurate encoding.

The only advantadge of AC3: you can get it throw your digital output. If you havn't digital output, go for MP3 and spare your time!
DSPguru
24th March 2002, 17:25
Originally posted by ChAoS Overlord
There really isn't much info about dolby surround downmixing in it... and what about the Audio FAQ ?
MaTTeR
24th March 2002, 17:28
Originally posted by bobotns

There is no specific MP3 settings, but you may choose STEREO instead of JOINT STEREO for 100% accurate Dolby Surround encoding.

Actually if you must encode to MP3 instead of Vorbis then I'd recommend using Joint Stereo. An average bitrate of >130kbps or so with Joint Stereo retains the DPL info quite nicely.

In Vorbis I'd highly recommend using Light Lossy or Lossless channel coupling to achieve basically the same DS effects as mentioned above. Just my opinion, perhaps do a short listening test of the various modes and let us know what you like.