[asterisk-dev] Asterisk video support

[Olle E. Johansson]

10 sep 2009 kl. 13.38 skrev Kevin P. Fleming:

> Vadim Lebedev wrote:
>
>> I think it would be good occasion to implement better handling of  
>> fmtp
>> attributes for streams
>> handled in transparent way.  I mean that if endpoint A  calling  
>> endpoint
>> B has a fmtp attribute in video stream descriptor it should be  
>> fowarded
>> to B by asterisk.
>> Today it is scrapped.
>
> No, it is not 'scrapped'. Asterisk is not a proxy, and for that reason
> there is *zero* expectation that an incoming channel's media format
> parameters are going to somehow magically be carried over to an  
> outgoing
> channel. The outgoing channel might not even have a way to express  
> those
> parameters, or the outgoing channel could *change* after the initial
> connection (due to transfers or other call control activities) in  
> which
> case the media format parameters may or may not be appropriate at all.
>
> While I certainly understand the desire for this to happen, doing it
> properly (without causing new breakage) will require the efforts we
> discussed at last year's AstriDevCon, ensuring that Asterisk can at
> least properly parse and understand the format parameters to the  
> best of
> its ability, so that it can match them up and determine when sets of
> parameters are 'compatible'. Just passing through the fmtp attributes
> does not provide any real solution except for some very small cases.
>
Seems like we are in agreement :-)

To understand Asterisk's video support today it's either ON or OFF by  
codec. No format specifiers for framerate, picture size or anything  
else are supported. Video is awfully more complex than audio, but even  
audio is beginning to be complex and require FMTP attributes, so we're  
getting there at some point.

With the videocaps code, that was created many years ago, John did try  
a method of an additional capability negotiation in addition to the  
codec negotiation. This work gave us a lot of insight in what is  
needed to get this right. With that branch, I could successfully set  
up calls between large Tandberg terminals in full size, or between  
different terminals in various sizes being negotiatied.

I do agree that we need to fix this at some point, and we've done the  
home work. Now we need resources.

/O