Re: [AVT] supporting variable picture sizes indraft-ietf-avt-rtp-h264-10.txt

["REHA CIVANLAR" <rcivanlar at ku.edu.tr>]

Let's say I am considering to send H.264 video with changing picture resolutions to a mobile device or a set top box.
If my target display, which I know to be  H.264 compatible,  is not capable of adjusting its final display size to a
constant resolution, I, probably, wouldn't want to use variable resolutions, because the end user will obviously
not be happy to watch video with changing picture sizes... (By the way, this argument applies to variable frame rates also.)
Moreover, even if the display device displays everything at a set resolution, I may still need to know what kind of
interpolation is being used for this purpose before deciding to use variable resolutions.

My question is shouldn't these be specified e.g., in the set of attributes for the end device? Should another standard
body be addressing this issue?

-Reha

>>> Dave Lindbergh <lindbergh at 92f1.com> 7/22/2004 3:49:42 PM >>>
Displays are outside the scope of H.264 - the standard covers only 
bitstream syntax and decoding.

So displays are free to show the decoded video any way they prefer - they 
can scale to the largest size, display in actual format, drop frames, 
whatever...

(A H.264 conformant decoder does not have to have a display at all.  Things 
like MCUs or recorders usually don't.)

--Dave


At 10:41 AM 7/22/2004, REHA CIVANLAR wrote:

>We noticed that in Section 1.2 of draft-ietf-avt-rtp-h264-10.txt seems to 
>imply that more than one picture size
>can be supported in the same video bitstream by toggling between two or 
>more parameter sets.
>
>The question is how is the decoder supposed to display video containing 
>varying picture sizes (e.g., does it interpolate
>all the pictures to do largest size?) Is this specified in any part of the 
>standard?
>
>
>
>------------------------------------------------------
>Prof. M. Reha Civanlar, Ph.D.
>Computer Engineering Department
>Koç University
>Istanbul, TURKEY
>+90 212 338 1719
>rcivanlar at ku.edu.tr 
>
>
>_______________________________________________
>Audio/Video Transport Working Group
>avt at ietf.org 
>https://www1.ietf.org/mailman/listinfo/avt 

----------
Dave Lindbergh
Polycom, Inc.
100 Minuteman Road
Andover MA 01810  USA
Voice: +1 978 292 5366
Email: lindbergh at 92F1.com 
H.320, H.323 video by arrangement


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