[vorbis-dev] Re: Ogg format and latency

[Ralph Giles]

On Sunday, May 18, 2003, at 12:58 pm, Beni Cherniavsky wrote:

>     Note also that a 'nil' (zero length) packet is not an error; it
>     consists of nothing more than a lacing value of zero in the
>     header.
>
>     -- http://xiph.org/ogg/doc/framing.html
>
> Not that somebody really needs them ;-).

Actually, they're fairly important for marking the end of a bitstream 
being generated on the fly. Think of something like subtitles from live 
transcription: the individual packets might be independent and you 
don't know when the last one will come. Disallowing zero-length data 
either places a constraint on the codec (basically that it be able to 
encapsulate zero-length data in a non-zero-length 'finished' packet) or 
that you hold the most recent packet/page until you either get another 
or the end of the stream...which *does* introduce latency beyond the 
packet level.

  -r

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