On Sun, Sep 10, 2000 at 08:51:26PM +0200, Roel VdB wrote:
>
> Sunday, September 10, 2000, 6:39:22 PM, you wrote:
> FK> But there are no controls to affect the switching more sensitively.
> FK> So, for instance, a switch can be added to set a penalty bitrate for
> FK> the MS coding theme:
> FK> -mS 10 use MS coding if it saves 10 kbps
> FK> -mS 20 use MS coding if it saves 20 kbps
> FK> -mS 200 use always LR coding scheme
>
> this is just what I was afraid of: fighting symptoms instead of
> a fundamental change. (-mx thread)
>
This model is much better than the hard switch to forced LR frames.
Currently there is a lot of music out there where 160 kbps with default
settings has the same or less quality than 128 kbps.
Take "One World" from "Dire Straits: Brothers in Arms" and listen to the
following settings:
$ lame -b128 music.wav music.128.mp3
$ lame -b160 music.wav music.160.mp3
$ lame -b160 -mj music.wav music.160j.mp3
The 160 coding suffers from the lack of MS frames. Stereo separation is a
little bit better than the 128 coding, but there are a little bit more
distortions. The 160j coding sounds not perfect, but a lot better.
> what is the use of sacrificing kbits in trade for assumed quality
> gains? There will always be pieces where even -mS 100 will not be
> enough, and you loose a lot of the use of JS.
>
Currently we have total loss of the advantage of MS for bitrates > 128 kbps,
even on digital mono files (L and R are 100% identically).
Pro/Cons LR:
+ more constant and predictable bitrate than MS
- often higher bit rate demand than MS
Pro/Cons MS:
+ often lower bit rate than LR
- very unpredictable and varying bitrate, so sometimes you
must switch to LR
- switching artefacts
The best parameter you know after coding, for instance:
Option Additional Info after coding
-b256 * nevertheless use MS, there are nearly no problems with MS, mask and
signal correlation is high, so NMR can be increased by "-mj"
-b128 * use LR, there is nearly no advantage of MS frames, only low
signal correlation, masks are often very different, reduce
upper frequency limit from 15 kHz to 14 kHz
-V0 * file size is increased by 1.2% by setting -b128, so use this option
* only two frames are 320 kbps, so also use -B256 to avoid problems
with some players
Have someone measured the coding delay for FhG and lame ???
How many PCM samples must be feeded to achieve the first MP3 frame?
May be FhG have a longer delay to see more of it's "future"?
--
Frank Klemm
--
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