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What do you mean by Channel coupling?, vorbis 6ch?
NeDtHeOnE
post Apr 2 2006, 07:59
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Does Vorbis 6ch has channel coupling support?

Vorbis stereo has channel coupling support .. But what good does it do?


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HotshotGG
post Apr 2 2006, 19:30
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QUOTE
Does Vorbis 6ch has channel coupling support?

Vorbis stereo has channel coupling support .. But what good does it do?


What what are you yelling about? biggrin.gif. There is no support for channel coupling with multichannel files encoded with Vorbis. If you do have a multichannel streams you need to use => -q 6 and up right now (where no channel coupling is used, it would be wise to use that anyway too). Stereo channel coupling mechanism is the most important part of libvorbis, due to the fact that's where the encoder get's it's most significant gains in terms of entropy coding. This is if you want to look at it in technical sense.

This post has been edited by HotshotGG: Apr 2 2006, 19:31


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NeDtHeOnE
post Apr 3 2006, 06:02
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But AAC 6 channel Audio has channel coupling...

Does that mean it is better 2 encode to 6 Ch AAC than 6 Ch Vorbis?


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kjoonlee
post Apr 3 2006, 06:55
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QUOTE (HotshotGG @ Apr 3 2006, 03:30 AM)
If you do have a multichannel streams you need to use => -q 6 and up right now (where no channel coupling is used, it would be wise to use that anyway too).
*

What do you mean? Running oggenc -q-1 on 6 ch audio will give you uncoupled output.


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LaserSokrates
post Apr 3 2006, 07:38
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Yes, however at these low bitrates, channel coupling gives you extra compression in a minimal loss in quality (I think... I could be stroke for TOS #8 here), however at q6 it's no more neccessary. So at q6 and up, it doesn't matter if you have 5.1 material for which oggenc can't use channel coupling because oggenc wouldn't use it anyway. But as nedtheone is focused on small filesizes, this solution doesn't help him.
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kjoonlee
post Apr 3 2006, 07:44
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LaserSokrates, for stereo files made by oggenc, channel coupling is always in use.


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LaserSokrates
post Apr 3 2006, 14:25
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I mixed it up. For -q 6 and up, it's lossless channel coupling. However, I don't know the real difference, but I imagine lossless channel coupling could be something like LAME's joint stereo (which is lossless, despite what some people claim).
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shadowking
post Apr 3 2006, 15:34
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I found something usefull here:

http://www.xiph.org/vorbis/doc/stereo.html


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Firon
post Apr 4 2006, 22:33
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Wasn't it changed to -q5 and up, LaserSokrates? Below that, it was lossy. I forget if it was -q5 or -q6, I know it was one then changed to the other at some point...
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kjoonlee
post Apr 5 2006, 02:44
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It was changed from

-q4.99 and below is lossy
-q5 and up is lossless

to

-q5.99 and below is a mix between lossy and lossless
-q6 and up is lossless


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shadowking
post Apr 5 2006, 02:57
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So coupling is like an advanced Mid Side coding. At Q6 its on in 'lossless' mode and in LAME mid side is also lossless I assume... In MPC mid side settings below --ms 15 are also lossy ?


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Firon
post Apr 5 2006, 22:46
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Thank you for clearing that up for me, kjoonlee.
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HotshotGG
post Apr 12 2006, 21:28
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QUOTE
What do you mean? Running oggenc -q-1 on 6 ch audio will give you uncoupled output.


This is news to me ohmy.gif. Did John33 fix it or something? also it's in the wiki don't people read that damn thing? this is why it was created in the first place so we could make the clarification and distinction easier. If that's the case then I need to change that.

This post has been edited by HotshotGG: Apr 12 2006, 21:29


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NeDtHeOnE
post Aug 7 2006, 16:06
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Ok I am back..

I've a question over here.. Is it good if i encode an ac3 6ch 448 kbps audio to an ogg vorbis 6ch audio at -q -1.0

Umm that would be around ~180 kbps nominal ...

n what about AAC at same bitrate..?

thx


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SebastianG
post Aug 7 2006, 17:28
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QUOTE (HotshotGG @ Apr 2 2006, 20:30) *
(...) with Vorbis. If you do have a multichannel streams you need to use => -q 6 and up right now (where no channel coupling is used, (...)

Are you sure? I thought that at -q6 and above the left and right channels are still interleaved and VQ-coded which accounts for inter-channel redundancy. So, either I'm wrong or you and me have different definitions of "channel coupling" in mind.

SebastianG
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haregoo
post Aug 7 2006, 17:35
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QUOTE (NeDtHeOnE @ Aug 8 2006, 00:06) *
Ok I am back..

I've a question over here.. Is it good if i encode an ac3 6ch 448 kbps audio to an ogg vorbis 6ch audio at -q -1.0

Current aoTuV is tuned only for stereo.
There is no point encoding ac3 to vorbis 6ch.
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NeDtHeOnE
post Aug 7 2006, 18:01
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So u mean to say its useless to encode to vorbis 6 ch? What if i want to preserve the 6 channel stream. which codec should i use? and seriously there is no way for good quality 6ch vorbis audio??


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haregoo
post Aug 7 2006, 18:50
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QUOTE (NeDtHeOnE @ Aug 8 2006, 02:01) *
What if i want to preserve the 6 channel stream. which codec should i use?

I also have the same question.

Best bet is ac3 at this time.(no quality decrease and reasonable bitrate)
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HotshotGG
post Aug 7 2006, 18:51
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QUOTE
So you mean to say its useless to encode to vorbis 6 ch? What if I want to preserve the 6 channel stream. which codec should I use? seriously there is no way for good quality 6ch vorbis audio??


Here is the deal. If you want to encode multichannel Vorbis streams, use a -q 6 and up. It's mentioned in the wiki. No channel coupling is used above -q 6. libvorbis needs to be rewritten in order to couple appropriate channel mappings for 5.1 and ambisonics below a -q 5. Rather than focus the developement efforts on consistently retuning the encoder, someone should focus on improving the source code to deal with that. The problem? nobody wants to do, because it's a time consuming task. wink.gif


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NeDtHeOnE
post Aug 7 2006, 18:56
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If i use -q6 then what do u think will be the file size? Bigger than the original AC3???


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HotshotGG
post Aug 7 2006, 19:08
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QUOTE
If I use -q6 then what do you think will be the file size? Bigger than the original AC3???


First of all attempt to speak in proper English and lastly don't be so abrupt and dismissive. It's not like you plan on releasing torrents or anything rolleyes.gif. I am just keeping you informed on the situation


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NeDtHeOnE
post Aug 7 2006, 19:16
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Not again!

I dont know why people from this forum tend to humiliate me all the time!

I love vorbis! i use it all the time for music or movie backup. All i want to ask is whether 6ch vorbis encoding is worth for movie backup?

I am sorry for my poor english. I am from India. I am trying my level best. And I know I am improving. I've seen people who want to improve and never do anything.


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HotshotGG
post Aug 7 2006, 19:21
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QUOTE
I love vorbis! i use it all the time for music or movie backup. All I want to ask is whether 6ch vorbis encoding is worth for movie backup?

I am sorry for my poor english. I am from India. I am trying my level best. And I know I am improving. I've seen people who want to improve and never do anything.


I understand that biggrin.gif . If you use a -q 6. You can't use less then a -q 6 right now as it stands. I have mentioned it several times before in this thread in the past. This is the type of thing that's difficult to improve, but it requires internal working knowledge of the low-level stuff. That's how it is.

QUOTE
Are you sure? I thought that at -q6 and above the left and right channels are still interleaved and VQ-coded which accounts for inter-channel redundancy. So, either I'm wrong or you and me have different definitions of "channel coupling" in mind.


I am pretty sure interleaving is still done. I have to dig through the source code again it's been a while. Everytime I look through it I figure out something new that I add in the wiki, so people aren't left in the dark. It's bit esoteric, because it's written in C and there are scarce comments here and there. You have to kind of guess what's going on.

This post has been edited by HotshotGG: Aug 7 2006, 19:31


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NeDtHeOnE
post Aug 7 2006, 19:28
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Thankyou very much HotshotGG! Ok Now can you please tell me more about AAC 6ch encoding sir?


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HotshotGG
post Aug 7 2006, 19:34
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QUOTE
Thankyou very much HotshotGG! Ok Now can you please tell me more about AAC 6ch encoding sir?


What questions did you have in mind? I don't use AAC very often, but if you were going to create a multichannel files for your movie that's the best way to go for what you plan on doing. EDIT: There are different implementations that support surround encoding. I know for a fact the Nero implementation does.

This post has been edited by HotshotGG: Aug 7 2006, 19:42


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