[xiph-rtp] Updated -04 Vorbis-RTP I-D

[Phil Kerr]

Hi Mike,

Michael Smith wrote:

>On Monday 13 December 2004 17:38, Phil Kerr wrote:
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>>I'm near ready to release an alpha of the server.  So far raw Vorbis
>>data streaming, packet fragmentation and aggregation, configuration and
>>metadata packet streaming works.  I'm now working on a codebook problem,
>>the API doesn't support access to the packed codebooks so I'm looking
>>for a way round.  Also I've not seen any way from libvorbis to get the
>>blocksize values for the identification header, any pointers on what
>>they do?
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>>
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>(a late response because my email is flaky... this message didn't arrive until 
>today).
>
>First question: Why are you trying to get the packed codebooks? I think it's 
>fairly unlikely that these will be interesting on their own. I would think 
>what you'd be interested in is getting the entire codebook setup packet 
>(which has the mode definitions, mappings, etc. as well as the codebooks 
>themselves) - and since that's just an entire packet, you don't need a 
>special API for it. Am I misunderstanding your needs here?
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Nope.  It does look a lot easier to use the unpacked codebook.

>If you really do need access to the constituent parts of the codebook header, 
>then yes - the libvorbis API has nothing here. You can use the library 
>internals, or just take bits of code (mostly in info.c, and various other 
>things called from there) from the sources, and adapt for your requirements.
>
>vorbis_info_blocksize() will give you the blocksize values (pass 0 and 1 as 
>the second argument to get the two different blocksizes). I wasn't quite sure 
>what you were asking here, when you asked what they do. Vorbis, like many 
>(most?) other block-based lossy audio codecs, has both short and long blocks 
>(this helps reduce pre-echo). Unlike many other codecs, the sizes in vorbis 
>are variable (though always powers of two), and so are sent in the header (In 
>the primary header, not in the setup header).
>  
>
Thanks for this info.  I was wondering what they did as well as getting 
access to the values.

-P

>Mike
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