Audio Encoding

[Whimick]

Hi All,

Does any know if you loose the surround sound encoding when you convert the MP2 stream from an MPEG2, to M2TS with AC3 Audio.

If so is there any way of keeding the surround sound coding.

Many Thanks
Whimick

[LoRd_MuldeR]

MP2 (MPEG Audio-Layer II) doesn't support more than two channels to begin with. Neither does MP3 (MPEG Audio-Layer III).

(AFAIK, there is an extension of MP2 called "MPEG Multichannel" that was initially madatory for European DVDs, but it was dropped later in favor of AC3)

[Whimick]

Hi Lord_Mulder,

Thanks for you reply.

I think you my have mis understood me.

If you look at http://www.bbc.co.uk/rd/pubs/papers/djm-ppr/djm-ppr.shtml

the indication is that they do.

My question about re-encodeing these streams.

Many Thanks

Whimick

[Ghitulescu]

I remember I managed to keep the surround sound, but when encoding from AC-3 to MP2/MP3 (long time ago, VCD times)

[Whimick]

Hi Ghitulescu,

Thanks for the reply.

I'm wanting to know if the Dobly coding in a MPEG2 stream (*.ts file) with an MPEG Audio (Version1)(Layer2) is lost during recoding to AC3.


Regards Michael

[LoRd_MuldeR]

Dolby Prologic just means that the origianl Sourround signal has been mixed down to Stereo (in a special way), so it can be stored/trasferred using only two discrete channels (and thus allows using MP2 or MP3 compression). At playback time, the decoded Stereo signal can be "upmixed" (split) to Sourround again, by using a Dolby Prologic decoder. Of course this won't give the same quality (channel separation) as using six discrete channels all the way (like AAC, AC-3 and DTS can do). Now if you re-encode such Dolby Prologic signal to AC-3, you could either keep the signal as-is and encode it with only two channels. You then get a Stereo AC-3 file that needs to be put through a Dolby Prologic decoder at playback time to get Sourround (I think the Prologic effect should surive the AC-3 compression). The other option is: You put the signal through the Prologic decoder before the re-encode and then encode it as 5.1 channels AC-3. In the latter case no Prologic decoder won't be needed at playback time to get Sourround.

[Ghitulescu]

Since you're encoding anyway, follow lord_mulders' advice and encode 4-5-6 dicrete channels, you need of course a decoder matching your source and a multi-channel ac-3 encoder.

[Whimick]

Hi All,

Thanks for the information it was very helpful.

AT present I use MeGUI to recode my *.ts TS Streams. So I hope that using AC3 encoder included wth MeGUI will work.

Regards Whimick.