[asterisk-dev] AST_FRAME_DIGITAL

[Russell Bryant]

Tzafrir Cohen wrote:
> One concern that Klaus raises and that you have not addressed is that
> you might want to transfer the frames with minimal changes from one
> channel type to another. 
> 
> How does this compare with RTP transport between various VoIP channels?

If the two channels are of the same type, then the streams could be transferred
with minimal changes using a channel driver's native bridge function.  An
equivalent example would be the various ways that chan_sip can do a native
bridge.  If the RTP stream is still going through Asterisk, it can still be
native bridged with very minimal effort using the "packet to packet" native
bridging method.

In the case of two different channel types, such as chan_zap to chan_misdn, then
I would need an example of what information could be lost, so that I can see if
we have a way to address it.  Frames already have a lot of information encoded
in them.  With a VOICE frame, for example, you have the frame data itself, a
subclass (the codec), and timestamp information.  I suspect that in the video
world, where things are much more complicated, there may be additional
information that there is no room for.

However, that gets into the discussion we had at the developer conference
pointing out the fact that we need to come up with a much more rich method of
describing formats so that we have an easier time supporting things like
wideband and video going forward.

Notes from that discussion at the devcon are here:

http://lists.digium.com/pipermail/asterisk-dev/2007-May/027890.html

-- 
Russell Bryant
Software Engineer
Digium, Inc.