Re: [rtcweb] Tim Panton's choices

Michael Procter <michael@voip.co.uk> Mon, 30 December 2013 16:35 UTC

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Date: Mon, 30 Dec 2013 16:35:10 +0000
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From: Michael Procter <michael@voip.co.uk>
To: Tim Panton <tim@phonefromhere.com>
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Subject: Re: [rtcweb] Tim Panton's choices
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On 30 December 2013 16:00, Tim Panton <tim@phonefromhere.com> wrote:
> Surely with ISDN the steps were quantized at 64kbps?

You would be surprised (or maybe you wouldn't).  From recollection,
the allocated bit-rate for video in a 2B ISDN call was basically
whatever was left over once you had chosen the audio codec, and used
some bits for alignment and other signalling.  I seem to recall 68.8
kbps was a common result.  If you mix in some LSD[0], then the
bitrates can get even more obscure.  See H.221 for more details if you
really need them.

The upshot of this is that there is probably a fair amount of
knowledge around dealing with changing bitrates for H.261 from the
ISDN community.

Michael

[0] Low Speed Data!