Vcd surround sound

vbimport

#1

when backing up to vcd, is surround sound possible? im backing up with: dvd decrypter, dvd2avi, tmpgenc plus. if its possible, what do i need to check in these programs.
thanx

dragon214


#2

MPEG Multichannel, a pretty obscure sound format, would be the only option, as a standard compliant VCD features MPEG sound. However, only a few DVD players can playback these MPEG Multichannel soundtracks from a VCD, most players just recognize it as a stereo MPEG track (as opposed to MPEG Multichannel on DVDs, which is supported by numerous European and Australian players).
If you live outside of Europe or Australia, chances are that there’s no hardware available to playback MPEG Multichannel tracks, as it was originally an alternative to Dolby Digital, which never made it into a standard.

If you search the internet, you might come across a program by Philips which transcodes Dolby Digital 5.1 tracks into MPEG 5.1. I tried it myself once, but my DVD player is one of those players that will only play it as a stereo track :frowning:


#3

thank you bob for that great detailed explanation. you dont know how much work you just saved me. thanx again
dragon214


#4

Hi,

hum, don’t know about the MPEG Multichannel. I though it was a replacement for AC3 in some countries, another way to zone in a certain manner but this tends to fall because dvd manufacturers(as for zoning process :slight_smile: ) did put all the hardware and software to cope with both formats. I found a thread here discribing what Crazy Bob talked about.

As far as I read on this subject, VCD isn’t as fancy and rich as SVCD or DVD. Quite limited specifications, no place for nice tweaks here. Audio and video formats are very restricted.
Maybe Crazy Bob is talking about some non standard tweaks as such involved to create so called XVCD or XSVCD, which could be taken by a few DVD players. See link above.

A safer (but much harder way) is to play regular VCD with audio modified in a way that in association with a dolby prologic or better amp (at least one which can expand simple stereo sound on all the 4, 5, 6, 7, (more ? :eek: ) speakers), sound will appear to be “surrounded”.

By using BeSweet, you can explode AC3 into some wav and tweak the stereo part by injecting with your favorite sound editor the front and rear channels as you want, thus producing simple stereo audio track, fully compatible with VCD standards.
But I know near to nothing about it: the surround is recreated by dolby surround amp by taking into account phase information which is small shift between left and right audio. I can’t talk any further as I know nothing beside that.
I believe to remember that some flavours of soundforge has a module which process multichannel audio.
And chances are all this isn’t necessary for usual purposes as BeSweet processes this automatically. Here for BeSweet AC3toMP2 tutorial

As I wrote this, I although crawled through the web and found this which is exactly what I thought about ! HeadAC3he v0.23a which allows you to fine tune all the speakers involved to produce (stereo) MP2.
Maybe a reason to forget what I wrote above.

One thing to conclude: audio phase information is often lost or worse, massacred when converting source to low bitrate MP3 using joint stereo (less with mid-side stereo, a lot with intensity stereo). MP2 is mpeg 1 layer 2 is worse than layer 3, and according to BeSweet, have to be encoded in joint stereo (don’t know if it is in the VCD standard or if it’s there to enhance the overall quality (aware of pro/cons of joint stereo vs simple stereo ? (pro) a way to distribute optimally the bitrate jugging on the stereo separation, (cons) sounds less stereo, loss of phase).

Pffiou I hope not scaring you too much (and although not talking nonsense !).

I have all the hardware to test but have some problems with it :a so don’t expect from me a fast “test reply”.
Have some sample tests (same sample video multiplexed with some according audio tweaked mp2 :slight_smile: ) and see by yourself. That’s what I will do when my hardware will cooperate.

Stay tuned, email notification on :wink:
Don’t hesitate to post here if something isn’t quite clear or to describe your hardware.
CIA.

MiRV


#5

Thanks MiRV, I’ll give that program a try, though I’m not convinced it’ll work, because of the great compression losses when converting to MP1 or MP2 (although the standard bitrate of a VCD is 224 kbit). I’m afraid (in advance) that the phase information for an MPEG 2.0 surround track (2 channel with phased information for a center speaker and a rear channel) will be lost when converting to a standard compliant VCD audiostream (similar to what you said).
Of course, most Dolby Digital receivers can put stereo sound on both the front and the rear speakers, but the effect isn’t exactly the same as an original 5.1 track, where you have 5 separate channels. With the “4 stereo” option (as it’s called on my receiver) you’ll hear everything from all sides, even dialogue, which normally (on 5.1 channel DVDs) comes from the center speaker.


#6

Hi Crazy Bob and dragon214,

hum I was quite busy these days, but I’ve began a huge post, not finished yet cause I need some more tests.

As a matter of fact, you are right Crazy Bob: multichannel is described and normalized but compatibility with existing dvd players is unknown.

More to come, stay tuned.

MiRV