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Originally posted by nico

I have to decide whether encoding the whole cd-archive in Vorbis 1.0 or in Vorbis GT3. Any experience?

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Originally posted by DonVorbis is made to be peelable, but there isn't a good working one yet.

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Vorbis is made to be peelable, but there isn't a good working one yet.

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Ogg Traffic for December 1, 2002 Jim Hines started a lengthy thread on November 7, 2002, by asking about the status of bitrate peeling. Bitrate peeling is the currently not yet implemented feature for reducing the bitrate (and thereby, size) of an Ogg Vorbis file by chopping off high-resolution data from the ends of packets to yield a smaller lower quality stream without decoding and re-encoding.

This feature is unique to Ogg Vorbis, and has very sexy applications:

In a streaming situation, the server would store only one high quality stream, and dynamically peel it down to the client's bandwidth.

It was pointed out that Real accomplishes roughly the same effect with its SureStream technology, but this is a weak comparison, as Jack Moffit clarified here. A SureStream server encodes the audio stream into different streams at discrete pre-set bitrates, and it can only switch between those pre-set bitrates. A dynamically peeling Vorbis stream server would be able to peel the stream down smoothly to fit the client's capacity as closely as possible, without causing huge jumps in quality.

As Daniel Schregenberger noted, once portable Ogg Vorbis players come into existence, you could store high quality Ogg Vorbis files on your PC for your Audiophile home theater setup, and peel them down to "good enough for lousy headphones on a noisy train" portable files.

Beni Cherniavsky mentioned a very intriguing counterpart to bitrate peeling. If you have a peeler that saves the bits it chopped off, you could reconstitute the higher quality files by adding the missing bits to the lower quality file. This idea could lead to a music download service where you can download a low quality preview version of a song, and if you are interested, download the missing bits to make it a high quality version.

Bitrate peeling is not actually implemented yet. A proof-of-concept tool exists, but it doesn't produce sufficiently satisfactory results on version 1.0 encoded Ogg Vorbis files. To work satisfactorily, bitrate peeling requires support on the encoder side, which takes time to write, and Monty hasn't had time to do that yet.

However, the amount of traffic that the bitrate peeling topic produced on the list prompted Monty to think harder about implementing it, and to give it a higher development priority.

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Ogg Traffic for Tuesday, April 15, 2003 Segher's experimental peeler (which was an April Fool's joke, by the way) has rekindled interest in a working bitrate peeler, as evidenced by this thread. The bottom line is that Version 1.0 files don't peel very well due to how the packets are organized.

Segher has plans to write a tool that will rearrange (losslessly, i.e. without additional re-quantization loss) a Vorbis file into a form that peels better. He is convinced that this can be done, but that takes time, which is something he doesn't have in excess. Of course, if somebody offered him a contract to implement bitrate peeling for money, the process could be accelerated a lot. Oh, and did I mention that donations to Xiph.org are now tax-deductible?

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