[speex-dev] frame size
joost at iliana.nl
Tue Dec 9 11:45:56 PST 2003
Je 2003/12/09(2)/13:12, Tom Grandgent skribis:
> Joost Witteveen (joost at iliana.nl) wrote:
> > So, each UDP package with 20 bytes speex-data, we send:
> > 20 bytes speex
> > 12 bytes ogg headers (and others?)
> > 28 bytes UDP/IP headers (2 IP numerbers, 2 portnumbers, checksum, etc, etc)
> > and, if it goes over the phone, each package has a few ppp headers.
> > Am I overlooking something, or does this fixed frame size mean that
> > the "8kbps" in reality means at least 24kbps?
> > Or is there something ohphone/gnomemeeting/etc can/should do to
> > put more than one fram inside each UDP package?
> Er, why would you be sending ogg headers in a VoIP scenario? That's
> needless overhead. Check out the Speex RTP format document at http://www.speex.org/drafts/draft-herlein-speex-rtp-profile-00.txt.
> Figure 1 and sections 3.2 and 5 show how to send multiple frames
> per packet.
When both gnomemeeting and ohphone gave me no options to put more
than one frame in the packages, I apparently too quickly assumed
that it was impossible to do.
So now I guess gnomemeeting/ohphone need to be patched.
> In my VoIP program, I use my own protocol (for now) and each
> packet currently works out like this:
> ~5 bytes - PPP
> 20 bytes - IP
> 8 bytes - UDP
> 1 byte - sequence number (my own)
> ~40-300 bytes - 4 Speex frames (VBR quality 6, wideband)
> I send at a rate of 12.5 packets per second, putting 4 Speex frames
> in each packet. This gives a total bandwidth usage of approximately
> 7.4kbps to 33.4kbps, which I think is pretty good for high quality
> wideband, and it works on a dialup modem.
Yeah, that seems sensible.
The ppp phone line I plan to use it over doesn't offer much more than
20bps, so I guess I cannot use gnomemeeting/ohphone as is now:(.
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