[asterisk-dev] AST_FRAME_DIGITAL

[Klaus Darilion]

Russell Bryant wrote:
> Klaus Darilion wrote:
>> Thus, if I have 3G video call bridged by Asterisk from chan_zap to 
>> chan_misdn Asterisk should decode the 3G video and then reencode it - 
>> does not sound well engineered.
>>
>> If Asterisk bridges a G4 fax call from chan_zap to chan_misdn Asterisk 
>> should decode the G4 fax into in an IMAGE and the reencode it to G4?
> 
> If you don't, then you are really defeating the purpose of using Asterisk in the
> first place.  Let me list a few small examples that would work if you do break
> the stream down into voice and video frames, but will not work if you pass the
> stream through as raw.  There are countless more ...
> 
> 1) What if you want to monitor the call via ChanSpy?  Specifically, what if you
> want to monitor the call from a channel type that is not an ISDN channel?

Works by using h324m_gw, then activyte ChanSpy and then before sending 
out reencode with h324m_call. Thus it is possible but not done 
automatically.

> 2) What happens if one caller wants to transfer the other to a non-ISDN channel?

This is more complicated but you can handle this in dialplan to. I guess 
the problem is "how to initiate a call transfer from a 3G mobile during 
a video call"? At least the Nokia 6630 can't do that. btw: I do not know 
any mobile which can initiates transfers.

> 3) What if you want to transfer the channels into a conference with other ISDN
> channels?  (Manager action redirect, for example)

Again this can be handled in extensions.conf - after transfer just check 
transfer capability and user information layer 1 (via func_channel) and 
depending on the values either conference directy or decode the 3G video 
call before using h324m_gw.

> I understand your desire to make this work.  I can also appreciate you seeing
> the "easy way" to do it, and pushing that direction.  However, what I and
> Tilghman have been trying to do is push this more toward the "Asterisk way" of
> doing this.  Asterisk is designed to be a channel technology independent
> application.  That means, it does not matter if it is ISDN or SIP or whatever
> else, it all looks the same inside of Asterisk.  This lets us build features
> that will work across any type of call.  What you are proposing completely
> breaks this architecture.  

It does not break complete - but you have to take care and specify 
routing twice: 1x for voice calls and 1x for video calls.

 > So, for a little bit of extra work and minor effect

IMO "little bit" is not correct. Getting used to all ISDN channel 
drivers is not done in a day.

> on performance, you can make this fit into the Asterisk architecture, bridging
> 3G ISDN voice and video calls to everything else that Asterisk has to offer.


I will prepare a patch for Asterisk and show you how your examples can 
be handled in extension.conf. I think this will explain more than all my 
emails.

regards
klaus