5.1 ogg audio stream in .ogm question

[encreept]

This is my first post in here, I've been reading the forum for quite some time but I haven't found any answer or solution. Here is the problem:
I rip a DVD title, using robot4rip and gknot, everything is ok, I've got great results in divx quality, no problems whatsoever. recently, i started using ogg compression for my music collection after noticing how good it sounds even at really low bitrates. I was thinking about using 5.1 ogg compression for the audio in my divx rips. I mostly use mp3vbr for 1 cd rips and ac3 for 2 cd rips. I've read that using 5.1 oggs isn't that good of an idea, but I've noticed that a 0.3 quality 5.1 ogg has the same file size as a 224kbps ac3 file, and it sounds significantly better.
So, I transformed the ac3 stream to 5.1 ogg using the BeSweet "OggMachine" front end. I play the .ogg file in media player or any other dirct-show compilant player, it plays just fine. I play it in winamp 2.91, it plays fine.
But when I mux it with the movie in an ogm container and play the ogm file with media player, I can only hear the front left and front right speakers from the audio stream!!! (no voices, no surround fx). The same thing happens when I play the file in other players like BsPlayer, Micro DVD etc. BUT, when I play the same file in winamp 2.91 (which has video support), the movie plays fine!!! all 5 channels are there, the sound is in sync with the picture...
So, any suggestions on this? It's a bit difficult for me to only play those files through winamp. They play fine in my P4 2.4Ghz but not so fine in my Athlon XP 1700+. Winamp video is so resource-hungry :)
Thanx!

[Animaniac]

The audio doesn't get downmixed, so you would need Trombettworks' Channel Downmix Filter (http://www.trombettworks.com/directshow.php) to get it to play on a speaker configuration with fewer channels, i.e. 5.1 to 2.1. If you have a 5.1 speaker configuration, the Vorbis channels may not be mapped correctly, this filter should be able to fix that as well (though I am not entirely certain about that).

[CaptainCarrot]

this filter should be able to fix that as well (though I am not entirely certain about that)
Be asured, this filter can remap any input speaker configuration to any output speaker configuration, it simply uses a matrix that tells it how much of a given input channel goes to a certain output channel.

[haibane]

I am pretty sure the media player classic's custom channel mapper can handle this, I have made some vorbis 5.1 encodes, only problem is that i have to turn the vorbis decoding precision to 16-bit, or it will result cracking sounds, and I have to update my sound card(audigy)driver to the newest to avoid a total system crash.....
hope that can help you...

[Atamido]

I think I am a bit confused by the talk about 5.1 Vorbis. I was under the impression that Xiph had not yet specified exactly how to do it. Would someone please answer these questions for me?

1. Is there an official way to encode 5.1 Vorbis?

2. Is the way it is done now a way that Xiph has specified it should be done?

3. Does 5.1 Vorbis encode to a single stream?

[encreept]

:) the "media player classic" custom channel mapping did it! (after changing the vorbis decoder setting to 16-bit output) thanx haibane.
I didn't try the channel downmixer though since I already use the "media player classic" on my Athlon machine (the latest versions are really stable and light), thanx to Animaniac and CaptainCarrot for their input.

Pamel, I don't know whether Xiph intended ogg to be used for 5.1 encodes and I don't think there is an official way to do it. But the -6ch switch is there in BeSweet ;) so why not use it?

I've read some opinions that ogg shouldn't be used for 5.1 encoding because it doesn't make good use of the bitrate like ac3 or aac does. Well, even at q 0.050 it sounds better to me than ac3 @ 224kbps. Plus, you can apply gain to the sound (using Dsp Guru's compression algorithms for example) without it sounding bad (I don't know about you, but I can hear some annoying compression artifacts if I maximize the volume in ac3 files)

Oh, and the output is a single file and it plays perfect on its own through any player.

[Atamido]

Well, looks like Xiph did define how to map channels for up to 6 channels here. (http://www.xiph.org/ogg/vorbis/doc/Vorbis_I_spec.html#id5509716) The only question now is whether or not it is being done properly. I will just assume it is.

[outlyer]

Originally posted by Pamel
I think I am a bit confused by the talk about 5.1 Vorbis. I was under the impression that Xiph had not yet specified exactly how to do it. Would someone please answer these questions for me?
It has been possible from some a long time ago, but not with acceptable results (bad mapping / higher-than-desirable-bitrates) IIRC the problem was (is) that Xiph wasn't very interested in 5.1 support, specially (the really demanded thing) channel coupling (and this is what would make the bitrate be "better used").

Maybe now that Theora is on the roadmap and OGM merged, they'll rethink.