Finally! tooLame gets updated

Reply #25 – 2003-03-05 22:25:43

Hi !

A few questions about vbr mode / PAM / surround

I've read somewhere that bitrates above 192 are better in order to preserve surround (DPL II) information when encoding with mpeg1 layer II.

- Does it mean that using toolame vbr mode, there are more risks to lose surround information (according to the doc, bitrates from 112 to 384 are used by vbr mode when encoding 48Khz source)?


2/ I have compared results of an encoding (short one, about 5min.) using toolame 0.2k vbr mode with PAM1 and PAM2 (quality factor = 10).

PAM 1 : average bitrate = 230
PAM 2 : average bitrate = 182

Why such a difference?
How to interprete it for constant bitrates ?
Is one of these PAMs better for preserving surround information ?

Regards,
FuPP

Finally! tooLame gets updated

Reply #26 – 2003-03-10 12:26:37

[fupp] I've read somewhere that bitrates above 192 are better in order to preserve surround (DPL II) information when encoding with mpeg1 layer II.
Sounds right. the more bits the better. It may just be because you need about 192kbps (at least) to make effective use of "dual channel" mode (below 192, dual channel mode sounds pretty bad, and often, to try and make it sound better, joint-stereo can be tried, and this totally wrecks surround information)

[fupp]Does it mean that using toolame vbr mode, there are more risks to lose surround information (according to the doc, bitrates from 112 to 384 are used by vbr mode when encoding 48Khz source)?
If toolame decides (in VBR mode) that 112kbps are all that are needed, then it means that there's not much going on in that particular section of audio.  So the bits that *are* there will probably capture the surround info OK.

I can certainly recommend the following article if you're trying to get a handle on surround sound and mpeg audio:
"Matrixed Surround sound in an MPEG digital world" by D.J.Meares


[fupp]I have compared results of an encoding (short one, about 5min.) using toolame 0.2k vbr mode with PAM1 and PAM2 (quality factor = 10).
PAM 1 : average bitrate = 230
PAM 2 : average bitrate = 182
Why such a difference?

No idea. What do you get if you use a VBR factor of 0?

[fupp]How to interprete it for constant bitrates ?
I would usually say the PAM2 is the better psy model, so it's estimate may be the more realistic one.

[fupp]Is one of these PAMs better for preserving surround information ?
No idea. I don't have any surround sound material or surround sound equipment to test it with.

mike_toolame

Finally! tooLame gets updated

Reply #27 – 2003-03-10 22:28:10

Thanks a lot for your reply Mike !

I actually only use stereo mode, would I get better quality using dual channel with such a bitrate (192) ?

I've read the article : it seems that encoding dolby sources "takes a slightly higher bit rate (compared to just two channel stereo) for the same audio quality". I would be curious to know what about prologic 2 which is a little bit different...

I've done a test : using PAM 1 with q=0, I get 140 kbits; with PAM 2, it's 122... My source is AC3, encoded to dlp2 mp2 with the use of besweet (DspGuru tool), and toolame of course  . Quiet strange, isn't it ?. I've seen (using a bandwith graph)  that PAM1 seems to offer more bandwith (frequencies are cut at 15.5-16 khz, instead of 15 for PAM2). Is it right, and if so, can it explain things ?

Thanks a lot again for sharing some of your time with me and for that nice piece of software !

Cheers,
FuPP.

Finally! tooLame gets updated

Reply #28 – 2004-03-20 06:25:39

Could somebody help me with setting Foobar to use tooLAME?

Right now when I try to use "-" to utilize stdin I get an error. I can however use "%s".

Also when I converted an AC3 to MP2 the length increased from 2:06:35 to 2:06:46. This file was sampled from 48KHz to 44.1KHz.  Why did this occur.

Finally are all of the following settings correct?