Re: [MP3 ENCODER] efficiently do multiple bitrates at once?
I'm probably going to use lame for icecast and I'd like to stream multiple bitrates of the same live music coming in the soundcard. Yep... Liveice does the multiple bitrate thing with enough coercion, but it does it by firing off multiple encoders. The thing is - unless the different bitrates have the same frequency and number of channels then surely they are too dissimilar after the resampling to gain very much? Well, the psycho acoustics should be the same :-) Ciao, Segher -- MP3 ENCODER mailing list ( http://geek.rcc.se/mp3encoder/ )
Re: [MP3 ENCODER] efficiently do multiple bitrates at once?
The thing is - unless the different bitrates have the same frequency and number of channels then surely they are too dissimilar after the resampling to gain very much? Well, the psycho acoustics should be the same :-) Some things might be similar, like m/s choice, block type decision, but the bit allocation is diffinitively different, as the number of bits available is different and frequency distribution is different due to filters. So yes, you'll probably gain something like 5-10%, but I personnaly think that it's not enough to justify an heavy code modification. Regards, -- Gabriel Bouvigne - France [EMAIL PROTECTED] icq: 12138873 MP3' Tech: www.mp3-tech.org -- MP3 ENCODER mailing list ( http://geek.rcc.se/mp3encoder/ )
Re: [MP3 ENCODER] efficiently do multiple bitrates at once?
On Mon, 19 Jun 2000, Segher Boessenkool wrote: [snip] is different and frequency distribution is different due to filters. You first filter and _then_ do the psycho acoustics? That's broken, IMHO. [snip] I don't agree, in MP3 the psycho acoustics are there to determine masking of distortion. I.e. I can handle 3db of noise in SFB4 because SFB5 is X loud and the distortion will be inaudiable. If you calculate the psycho acoustics before filtering you might assume masking that doesn't exist. -- MP3 ENCODER mailing list ( http://geek.rcc.se/mp3encoder/ )
Re: [MP3 ENCODER] efficiently do multiple bitrates at once?
Some things might be similar, like m/s choice, block type decision, but the bit allocation is diffinitively different, as the number of bits available This stuff is not psycho acoustics itself. psycho is: window, fft, cb's, energy tonality computation, spreading function, threshold computation. After that you use it: fold to sfb's, m/s choice, ... is different and frequency distribution is different due to filters. You first filter and _then_ do the psycho acoustics? That's broken, IMHO. The filtering is done before. In psychoacoustic, (and also in psychovision) what is more annoying is not artifacts themselves, but changes in artefacts. High frequency limit change IS an annoying artefact. If the filtering was done after psycho acoustic, it would mean that the high freq limit could change from a granule to another, leading to a kind of high freq fluttering. So I'm quite sure you wouldn't gain 50% in re-using computations. This is my opinion, perhaps others could tell us what they think about it. Regards, -- Gabriel Bouvigne - France [EMAIL PROTECTED] icq: 12138873 MP3' Tech: www.mp3-tech.org -- MP3 ENCODER mailing list ( http://geek.rcc.se/mp3encoder/ )
Re: [MP3 ENCODER] efficiently do multiple bitrates at once?
You first filter and _then_ do the psycho acoustics? That's broken, IMHO. The filtering is done before. In psychoacoustic, (and also in psychovision) what is more annoying is not artifacts themselves, but changes in artefacts. High frequency limit change IS an annoying artefact. If the filtering was done after psycho acoustic, it I second that. would mean that the high freq limit could change from a granule to another, leading to a kind of high freq fluttering. Why would it change? You can fix the frequency... So I'm quite sure you wouldn't gain 50% in re-using computations. I think it could be... ...but it's not worth it. I'm not going to code it, anyway. This is my opinion, perhaps others could tell us what they think about it. Ciao, Segher -- MP3 ENCODER mailing list ( http://geek.rcc.se/mp3encoder/ )
Re: [MP3 ENCODER] efficiently do multiple bitrates at once?
On Mon, 19 Jun 2000, Segher Boessenkool wrote: [snip] is different and frequency distribution is different due to filters. You first filter and _then_ do the psycho acoustics? That's broken, IMHO. [snip] I don't agree, in MP3 the psycho acoustics are there to determine masking of distortion. I.e. I can handle 3db of noise in SFB4 because SFB5 is X loud and the distortion will be inaudiable. If you calculate the psycho acoustics before filtering you might assume masking that doesn't exist. Ok. But then, you really should do the psychoacoustics _after_ you have done the quantization. Oops, did I just here the universe implode? ;-) Dagdag, Segher -- MP3 ENCODER mailing list ( http://geek.rcc.se/mp3encoder/ ) -- MP3 ENCODER mailing list ( http://geek.rcc.se/mp3encoder/ )
Re: [MP3 ENCODER] efficiently do multiple bitrates at once?
On Sat, 17 Jun 2000, Gabriel Bouvigne wrote: Moreover, if the sampling rate is the same, if you change the bitrate, the frequency cut-off will be different. Are the frequent cut-offs different at the higher bitrates, like 96, 128 and 192? (Yes admittedly I probably won't be streaming over 128kbit/sec, but I'm curious.) -Sidi -- MP3 ENCODER mailing list ( http://geek.rcc.se/mp3encoder/ )
Re: [MP3 ENCODER] efficiently do multiple bitrates at once?
Are the frequent cut-offs different at the higher bitrates, like 96, 128 and 192? (Yes admittedly I probably won't be streaming over 128kbit/sec, but I'm curious.) Yes they are. It would be silly to try encoding full frequency range at 96. Regards, -- Gabriel Bouvigne - France [EMAIL PROTECTED] icq: 12138873 MP3' Tech: www.mp3-tech.org -- MP3 ENCODER mailing list ( http://geek.rcc.se/mp3encoder/ )
