Subject: [rtcweb] h.261 oddities

From: David Singer <[email-masked]>
Date: Thu, 02 Jan 2014 11:59:55 -0800

(changing the subject as this is discussion, not a poll response, as requested by the chairs)

On Dec 28, 2013, at 15:06 , Stephan Wenger <[email-masked]> wrote:

> Interestingly enough, H.261 *never* had a set of picture parameters that
> bear a relationship with source formats dominant in the market.
> CIF has 288 lines, QCIF 144, both distinctly non NTSC world.  OTOH, the
> frame rate is 1/29.97 Hz fractions thereof, definitely not PAL/SECAM.
> This is the result of a standardization compromise of the worst sort.
> Note that this hasn¹t hindered the adoption of H.261 much.  Perhaps
> because, at the time, there were literally no alternatives.  Today there
> are.
> Stephan
> 

When we had H.261 in quicktime, we used the ‘system layer’ to give timing, and hence any frame rate, and we also externally tagged the actual picture size (and padded up the encoding). I seem to recall you can do the same in RTP.

Whether H.261 is something I ever want to watch again is another question entirely.

David Singer
Multimedia and Software Standards, Apple Inc.