stephen botzko <stephen.botzko at gmail.com> writes:
>>>>
>This is a real-world case; devices often have more encode horsepower (and
>camera resolution) than they can actually display when receiving, and they
>talk to other devices that *can* display that extra resolution..
>>>>
>
>In our experience, the reverse situation is what actually happens - PCs for
>instance frequently can decode and display HD images, but are often limited
>to an SD webcam.
>Can you name a couple of specific real devices that have these HD
>cameras+encoders and the limited decoders?
Mostly I'm not talking PC's (I agree with you there, though there are cases
where it still may make sense, like when displaying video in a portion of
the screen). I'm mostly talking mobile and dedicated devices with built-in
LCDs; that would include Smartphones, dedicated videophones, "media"
tablets, etc.
For example, certain devices have been made with two different LCDs; one
~850x480, the other ~480x234, both with VGA-class cameras. Sending VGA
content (or really anything beyond CIF) to the 480x234 display is just a
waste of bits. If you wanted to and could negotiate it properly, though,
you could send higher framerate CIF to that device, while it sends VGA at a
lower framerate to a device that can show it.
As for the comment about max-level=NN versus level-upgrade-allowed: I'd
originally thought level-upgrade-allowed made the most sense, and in fact
probably it does - let the answer respond with the highest level they can
receive, and the offerer can send at whatever level they support.
That's even easier to describe:
level-upgrade-allowed=0 or 1:
If the offer sets level-upgrade-allowed to 1, then an answer may
include any level above the offered level in profile-level-id.
The offerer may send at any level up to the level in the answer,
and and answerer can send levels only up to the level in the
offer. If this is not present or is set to 0, then the answer
MUST NOT respond with a level greater than the level in
profile-level-id.
Note that this only allows the level to be increased in the
answer; the profile and constraints are not allowed to change.
--
Randell Jesup, Worldgate (developers of the Ojo videophone), ex-Amiga OS team
rjesup at wgate.com
"The fetters imposed on liberty at home have ever been forged out of the weapons
provided for defence against real, pretended, or imaginary dangers from abroad."
- James Madison, 4th US president (1751-1836)