[vorbis] streaming ogg audio

[TIMMERMANS ANDRE]

> -----Original Message-----
> From:	Akos Maroy [SMTP:darkeye at tyrell.hu]
> Sent:	Wednesday, June 26, 2002 9:14 PM
> To:	vorbis at xiph.org
> Subject:	Re: [vorbis] streaming ogg audio
> 
> figyu wrote:
> > so, if i listen to a streamed ogg file (enter url into winamp, eg), the seek
> > bar never shows up, nor the position of where the playback is at any given
> > moment. the file length is also not known or shown. you can only stop it and
> > start again right from the beginning.
> > however, this all works with an mp3.
> 
> does it? my experience is that you can not seek with mp3 streaming 
> either, and certainly you can't seek into a live stream.
> 
> > we would need this to stream ogg for a radio station, but listeners would
> > not possibly put up with this not-being-able-to-seek-anywhere.
> > is it because of certain winamp shortcomings with vorbis streams or is it
> > down to ogg vorbis rc3 solely?
> 
> No, this is the nature of streaming mp3s as well. Basically, mp3 
> streaming is done by HTTP requests, reading a huge mp3 file from the web 
> server a piece at a time. As there are no additional commands than 
> standard HTTP, you can't send any special stuff like seeking into a 
> file, etc.
> 
Yes but the file duration of an mp3 file is generally easy to determine:
- for non-VBR files you derive a good estimation from the file size
  (from figyu's case I figure it's just winamp downloading files of known size)
  and the bitrate. I have never seen it differ more than a fraction
  of a second for 10-15mins files (the same cannot be said for
  ogg files, I made the test).
- VBR files usually come with a file header which provides
  the duration of the file.

Also Winamp may maintain a copy of the file on disk in which case
it can seek freely within the already downloaded part of the mp3 file,
it could also be done for an ogg file but without the file duration
how is winamp going to display a seek bar.

I think that putting the file duration in the Ogg/Vorbis headers
would be a very useful addition.

André

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