Re: [rtcweb] Is support for non square pixels MTI

[Randell Jesup <[e-mail]>]

On 8/25/2016 9:20 AM, Cullen Jennings wrote:
> I was trying to figure out from the specs what the story is on WebRTC support for non square pixels (for example CIF resolution video is often not quite square pixels).
>
> Thoughts on what the specs should say on this ? Anyone know what browser do today?

Yeah... ugh.  So most cameras *now* are square pixels.  Non-square pixel 
support would allow things like 640x240 (or 320x480) at 2:1/1:2 ratios 
as well.  Some much older cameras are the 10:11-ish ratios that also 
apply to BT.601/etc (see 
https://en.wikipedia.org/wiki/Pixel_aspect_ratio) and HDV/HDCAM (1.3 -- 
1440x1080).

So we should be defining how MediaStreamTracks and PeerConnections deal 
with this.  Must all MSTs be square pixels always?  (and what if the 
source just isn't, must it be converted to square at the input point 
(typically GetUserMedia)?  Can PeerConnection carry a non-square-pixel 
stream (separate from the MST requirement) for use outside of the W3 
environment?  If so, how is it signaled?  (I suspect there's some way to 
do so in the SDP, haven't checked).

If non-square are allowed in MSTs, we need to define some property of 
the stream so the <video> element can correctly display it.

There's work no matter which we select, though likely less in total if 
we mandate square pixels everywhere - though it loses some capability.  
And I think we need to say something (here and/or in the W3).  Passing 
data without any indication as the ratio (if it's not fixed as square) 
is just a mess, and where we are today.

-- 
Randell Jesup -- rjesup a t mozilla d o t com
Please please please don't email [e-mail]!  Way too much spam