mp2 file

[bugeyes]

I have an audio mp2 file generated
by ReMpeg2.
Hou can I know what kind of
audio file was encoded, a WAVE
file or an AC3 file?
How can I desencode from this file
the original soud track?

[bugeyes]

I will try to pose my thread more clearly.

I used ReMpeg2 to lower the bitrate from an AC3 file
and i got a mp2 (or mpa) file that I would like
to test to see if the AC3 channels are right positioned.

Since this file is a mpeg encoded AC3 file (i suppose)
and cannot be opened by HeadAC3he, Azid, or any other
AC3 processor, I pose the question:

Wich software can I use to decode the AC3 (or else) file that
is mpeg encoded in this mp2 (or mpa) file?

Thanks for your help.

[Zhnujm]

only some ideas, maybe im wrong:
i dont think rempeg can reencode an ac3 file, you will get a mpeg-2 audio file. you can convert a mpa file with besweet to wav/mp3, but i dont know if it supports multichannel mpeg audio.
i would try to play the mpa file with a soft-dvd player to test the channels

[Pojken Purken]

AC3 (Dolby Digital) and MPEG are two different ways of encoding and compressing your audio. One type can't be "compressed" with the other, they can only be converted between each other. Although I've read somewhere that MPEG supports multichannel audio there are no software implementations of this yet (please, correct me if I'm wrong). I therefore assume that what you have is a 5.1 Dolby Digital encoded audio stream (.ac3) converted and downmixed to a 2 channel MPEG1 Layer II audio stream (.mp2). This audio file should be easily playable in both Media Player and Winamp.

Regards
PP

[DSPguru]

Originally posted by Pojken Purken
Although I've read somewhere that MPEG supports multichannel audio there are no software implementations of this yet (please, correct me if I'm wrong). read q13 at the Audio FAQ (http://forum.doom9.org/showthread.php?s=&threadid=7633).

[Pojken Purken]

I bow to the guru and I stand corrected :D What decoder do I use to play back such a multiple MPEG-stream?
/PP

EDIT: Aaah, the Philips encoder that's mentioned should actually be decoder, shouldn't it?

[DSPguru]

Phillips' pub_enc will encode 6ch aiff to MultiChannel mpeg.
the mpeg can be played with WMP.

[bugeyes]

To suppose that ReMpeg2 could reencode an AC3
to a lower bitrate AC3 must be a common mistake
if you are a newbie.

There are a lot of sites where ReMpeg2 is told
to do that. It's not the case of Doom9 as I could see.

I know clearly that mp2,mp3,AC3 and DTS are compressed
files, and that the sound quality is a direct
function of the bitrate.

Thanks to all, and specially to the gurus patience.