When to use joint-stereo versus stereo

[mkanar]

This is a quote that I just got from 'Cokes' in the audio encoding forum:

But what DVD,SVCD a VCD concerns (MPEG-1(2) Layer 2 audio): Layer 2 doesn't know anything about MS, it uses only IS, so if you encode your Dolby Surround donwmixed audio in Joint Stereo mode of any Layer 2 encoder - it destroys surround information.

I thought that this information might be informative to many of the follow SVCD encoders here. Might be nice to add this info to the faq unless it's already there.

Actually, it would be kinda' convienent if DVD2SVCD defaulted to stereo or joint stereo depending on whether a 2 or 6 channel track is selected.

Thanks!
MKanar

[dragoman]

Hi,

Joint stereo often can be a good choice at lower bitrates. I believe it's the default with Lame at 128kps or below.

dragoman

[DDogg]

I want to be a little careful with this as people might get confused.

"...so if you encode your Dolby Surround donwmixed audio in Joint Stereo mode of any Layer 2 encoder - it destroys surround information."

Always use Stereo when it comes to MP2 unless you have some type of unique need. While there could be exceptions, 99.9 % of people need to not change the default.

[Cokes]

Originally posted by DDogg
I want to be a little careful with this as people might get confused.

"...so if you encode your Dolby Surround donwmixed audio in Joint Stereo mode of any Layer 2 encoder - it destroys surround information."

Always use Stereo when it comes to MP2 unless you have some type of unique need. While there could be exceptions, 99.9 % of people need to not change the default.

IMHO 128 kbps MP2 without joint stereo (here without intensity stereo) must sound ugly :)...
And I mean the last acceptable bitrate for MP2 stereo is 192 kbps and it could be maybe 160 kbps too (and thus Dolby Surround compatible).

I quote Mike Cheng - creator of toolame(http://members.dingoblue.net.au/~mikecheng/layer2/README.VBR):
"Currently VBR also forces STEREO mode (there's some extra stuff going on in main_bit_alloc() when j-stereo is turned on, and I don't want to mess with it just yet)."
"44.1khz with VBR ranging from 192 to 384."
"For the 32/44khz sampling rate, there probably is some merit in extending it at least down to 160, but the work require to do so is major (alloc tables need to be switched in and out)."

[Mozart]

@cokes

you misunderstood the following:
the mp2 audio used by dvd2svcd is CBR. Can you see it? CBR. Not VBR.

it doesn't make sence to use mpeg1 layer II with VBR to make (S)VCD audio tracks. The VBR audio for SVCD is mpeg2.

Those Chang's quotes are surely about the VBR option. Thus, they have nothing to do with SVCD audio encoding.

[DDogg]

... 99.9 % of people need to not change the default [in DVD2SVCD]

I should have been more clear. I am speaking of a DVD2SVCD encode of a DVD. Always use stereo.

[Cokes]

EDITED: This should be for Mozart...

Don't think:

First, I pointed out conjuction between stereo mode and bitrate. I understand Mike's words so: he doubts that stereo mode with present psychoacoustic model of toolame has no sense with bitrates under 160 kbps.

Second, neither MPEG-1 Layer 2 or MPEG-2 Layer 2 specifications says nothing about VBR mode.

VBR mode has nothing to do with MPEG-2 specifications.

MPEG-2 BC (ISO/IEC 13818-3) provides a backwards compatible (BC) multichannel extension to MPEG-1; up to 5 main channels plus a 'low frequent enhancement' (LFE) channel can be coded; the bitrate range is extended up to about 1 Mbit/s; an extension of MPEG-1 towards lower sampling rates 16, 22.05, and 24 kHz for bitrates from 32 to 256 kbit/s (Layer I) and from 8 to 160 kbit/s (Layer II & Layer III).

CBR or VBR modes don't interest us at this point, we speak about single packets.

[Mozart]

what about if you read carefully chang's words quoted by yourself? Every sentence has "currently VBR does something..." ,or "something with VBR is...". How can you say that VBR has nothing to do with his (and your) statements? Are you blind?


cokes said:
vbr mode has nothing to do with mpeg-2 specificationReally?Are you sure?LOL

[Cokes]

Originally posted by Mozart
what about if you read carefully chang's words quoted by yourself? Every sentence has "currently VBR does something..." ,or "something with VBR is...". How can you say that VBR has nothing to do with his (and your) statements? Are you blind?

O-ou, the first question sounds: Why toolame by VBR encoding uses only stereo (not IS)? Because there's some extra stuff going on in main_bit_alloc() when j-stereo is turned on, and I don't want to mess with it just yet.
The second and principal question is: Why then toolame (in stereo mode) goes not under 192 kbps?

Really?Are you sure?LOL

Oooh let me guess. :D ...or no, don't let me guess and show me some ISO/IEC documents with words "VBR" and "MPEG-2 Layer 2"...
That's what I'm pretty sure this couldn't be a knot for you... ;) when we spoke about who's sure and LOL and who's not.

[DDogg]

Cokes, I still don't understand the point of this post. If it is that a person should not do a bitrate under 160 when using DVD2SVCD I would agree. [and it should always be stereo to preserve the surround mix]

[Cokes]

DDogg, sure that's all about. :)

[DDogg]

Then you make an excellent point. Thanks :)

[Mozart]

I´m sorry Ddogg, but this guy cannot make wrong technical assuptions and be congratulated by this;)

Reading Chang´s readme file, anyone can clearly see that he is talking about the limitations/fragilities of his own program, when such program is used in VBR mode.

took from toolame readme.vbr file linked by Cok

*** NOTICE ***
VBR mode is currently fragile and experimental. It works in simple situations on 32/44/48khz files.



I do know that my english is not so well wrote. However, I don´t have any problems to understand the sence of those words.:rolleyes:

[DDogg]

If it is that a person should not do a bitrate under 160 when using DVD2SVCD I would agree. [and it should always be stereo to preserve the surround mix]

I think he agreed with this. As for the other you guys duke it out although I would prefer this thread to just DIE! :)

[DDogg]

Cokes, DON'T EVER go back and edit a thread where you are auguing with somebody and they have replied to you. VERY, VERY bad form.



YOU know better :angry:

Thread closed!