Greetings, I was wondering some things: For a internet radio-station (e.g. using mp3 and hopefully using ogg soon), appart from the basic 'streaming' functionallity, there are two things that are also important - mixing music - 'downgrading' a signal to a lower datarate. Concerning 'mixing' music, it would be interesting to be able to mix two ogg-files without the need to decode and re-encode the files? Also, can it be done to mix vorbis-file with different data-rates? Concerning 'datarate downgrading', concider a radio-station doing streaming a different data-rates (128 Kbps for cable or ADSL; 80 Kbps for dual-band ISDN, 60 Kbps for ISDN, 40 Kbps for modem, ...). SO, it would be nice to able to 'downgrade' a (say) 128 KBps to the lower datarates without having to decode and re-encode the signal. Can this be done with vorbis? Cheerio! Kr. Bonne. -- KB905-RIPE Belgacom IP networking (c=be,a=rtt,p=belgacomgroup,s=Bonne,g=Kristoff) Internet, IP and IP/VPN kristoff.bonne@skypro.be Faxbox : +32 2 2435122 --- >8 ---- List archives: http://www.xiph.org/archives/ Ogg project homepage: http://www.xiph.org/ogg/ To unsubscribe from this list, send a message to 'vorbis-request@xiph.org' containing only the word 'unsubscribe' in the body. No subject is needed. Unsubscribe messages sent to the list will be ignored/filtered.
> Concerning 'mixing' music, it would be interesting to be able to mix two > ogg-files without the need to decode and re-encode the files? > Also, can it be done to mix vorbis-file with different data-rates?It shouldn't be too hard to have two separate Vorbis streams that get mixed by the player but I don't think there's any software that does that yet.> > Concerning 'datarate downgrading', concider a radio-station doing > streaming a different data-rates (128 Kbps for cable or ADSL; 80 Kbps for > dual-band ISDN, 60 Kbps for ISDN, 40 Kbps for modem, ...). > > SO, it would be nice to able to 'downgrade' a (say) 128 KBps to the lower > datarates without having to decode and re-encode the signal. >"Bitrate peeling" is planned but AFAIK there are no implementations yet.>From what I've gathered, the encoder needs to be designed to place the mostsignificant information at the start of each packet. Then it becomes as simple as having a server that chops packets according to the desired bitrate. Can't wait to see it! Aaron --- >8 ---- List archives: http://www.xiph.org/archives/ Ogg project homepage: http://www.xiph.org/ogg/ To unsubscribe from this list, send a message to 'vorbis-request@xiph.org' containing only the word 'unsubscribe' in the body. No subject is needed. Unsubscribe messages sent to the list will be ignored/filtered.
At 10:31 PM 2/15/01 +0100, you wrote:>Greetings, > >I was wondering some things: >For a internet radio-station (e.g. using mp3 and hopefully using ogg >soon), appart from the basic 'streaming' functionallity, there are two >things that are also important >- mixing music >- 'downgrading' a signal to a lower datarate. > >Concerning 'mixing' music, it would be interesting to be able to mix two >ogg-files without the need to decode and re-encode the files? >Also, can it be done to mix vorbis-file with different data-rates?It'd be interesting to do so, but I don't think it'd be particularly possible.> >Concerning 'datarate downgrading', concider a radio-station doing >streaming a different data-rates (128 Kbps for cable or ADSL; 80 Kbps for >dual-band ISDN, 60 Kbps for ISDN, 40 Kbps for modem, ...). > >SO, it would be nice to able to 'downgrade' a (say) 128 KBps to the lower >datarates without having to decode and re-encode the signal.Yes - this is one of the really nice features of the vorbis format. However, tools to do it don't yet exist (they're planned for 1.0, though). Michael --- >8 ---- List archives: http://www.xiph.org/archives/ Ogg project homepage: http://www.xiph.org/ogg/ To unsubscribe from this list, send a message to 'vorbis-request@xiph.org' containing only the word 'unsubscribe' in the body. No subject is needed. Unsubscribe messages sent to the list will be ignored/filtered.
Well nobody else has answered this so I thought I'd take a shot. - If you want to mix the Vorbis bitstreams somehow in their final state (Huffman compressed into packets or whatever), that would surely be impossible. Nothing at all lines up, it is just random compressed data at that point. - You could try decoding the Huffman data so that you are left with frequency domain data for each Vorbis stream. It is possible to mix quite easily in the frequency domain. However, it is probably not possible to mix two Vorbis streams in the frequency domain easily, because I believe a Vorbis stream is comprised of "short" and "long" blocks. I think you can only add together blocks if they are the same size. I'm sure no two streams would line their blocks up that well, so you would have to recalculate the appropriate block sizes. Even if this technique worked it would use a lot of CPU anyway, all you are really gaining is saving the conversion of 2 streams to PCM and back to frequency domain again. I'm not sure exactly what state the data may be mixable other than the raw frequency domain data either, it may be possible to mix earlier. - The 3rd and pretty much only option that would work would be to just have 2 fully functional decoders hooked up to a mixer, and the encode again. That would be a huge amount of CPU for a server though. If you could just store your source audio as PCM, and mix that and then encode on the fly, that would save a good deal of CPU time. The same arguments would probably apply to any frequency domain type of compression (MP3, AAC, etc.). Well I don't really know that much about the Vorbis format so correct me if I am wrong on any points. Thanks, Dave. -----Original Message----- From: jaromil [mailto:jaromil@dyne.org] Sent: Monday, February 19, 2001 2:56 AM To: vorbis@xiph.org Subject: Re: [vorbis] mixing and 'downgrading' of vorbis-files On Thu, Feb 15, 2001 at 02:40:29PM -0700, Aaron Porter wrote:> > Concerning 'mixing' music, it would be interesting to be able to mix two > > ogg-files without the need to decode and re-encode the files? > > Also, can it be done to mix vorbis-file with different data-rates? > > It shouldn't be too hard to have two separate Vorbis streams that getmixed> by the player but I don't think there's any software that does that yet.muse does it: http://muse.dyne.org (in the pcm domain doe) jrml --- >8 ---- List archives: http://www.xiph.org/archives/ Ogg project homepage: http://www.xiph.org/ogg/ To unsubscribe from this list, send a message to 'vorbis-request@xiph.org' containing only the word 'unsubscribe' in the body. No subject is needed. Unsubscribe messages sent to the list will be ignored/filtered. --- >8 ---- List archives: http://www.xiph.org/archives/ Ogg project homepage: http://www.xiph.org/ogg/ To unsubscribe from this list, send a message to 'vorbis-request@xiph.org' containing only the word 'unsubscribe' in the body. No subject is needed. Unsubscribe messages sent to the list will be ignored/filtered.