Rockbox mail archiveSubject: Re: MPEG Audio format
Re: MPEG Audio format
From: Bluechip <csbluechip_at_gmail.com>
Date: Sat, 14 Jan 2006 06:05:00 +0000
At 04:39 14/01/2006, you wrote:
>I just ran lame with no options on the first file I found and got the
>LAME version 3.96.1 (http://lame.sourceforge.net/)
>CPU features: MMX (ASM used), SSE, SSE2
>Using polyphase lowpass filter, transition band: 17249 Hz - 17782 Hz
>Encoding concat.wav to concat.mp3
>Encoding as 44.1 kHz 128 kbps j-stereo MPEG-1 Layer III (11x) qval=3
> Frame | CPU time/estim | REAL time/estim | play/CPU | ETA
> 2379/2381 (100%)| 0:09/ 0:09| 0:10/ 0:10| 6.2245x| 0:00
>average: 128.0 kbps LR: 849 (35.64%) MS: 1533 (64.36%)
>Writing LAME Tag...done
>As you can see on the line starting with "average" this particular sample
>used joint-stereo on 64% of the frames.
>If you don't have lame installed or can't find a track that produces both
>kind of frames, I can easily put this file somewhere.
LR: 849 (35.64%) MS: 1533 (64.36%)
Means that 64.36% of the Joint Stereo frames utilise the "+MS" thing ...I
have no idea what it is, but I do know it is a Joint Stereo enhancement
held in the MODE bits of the header - which are only relevant if the
CHANNEL bits are set to Joint Stereo. There is also a "+IS" (intentsity
stereo) and the combo "+M/S +IS"
> > >When it comes to sample rate, layer and version switching, I think you're
> > >reasonably safe, though it is probably legal. Stereo mode I think you
> > >find encoders may switch from frame to frame.
> > Is anyone in a position to send me an example file please? Or seond-best,
> > name an encoder with a required set of options.
> > Difficult to test my app without test data - and quite a chore to
> > manufacture such a file by hand. (...and that bit of the app is not yet
> > written)
> > BC
Received on 2006-01-14