[Asterisk-video] how to configure app_conference

[Mihai Balea]

Hi Borja,

Having full VAD in appconference is actually a feature I am interested  
in -- I just didn't have the time to do it.
It should actually be quite simple to implement - if you want to go  
ahead and attempt to do it, I would be more than happy to merge in  
your patch.

Here are a few pointers that might help you understand what needs to  
be done:
- the place you want to look at is member.[ch]
- if you look at create_member(), you will notice that members marked  
as 't' (telephone) have a speex preprocessor instance associated with  
them.  As the code stands right now, members coming in via a zaptel  
connection cannot do DTX (obviously), so appconference does VAD, AGC  
and noise reduction by itself.
- however, if a member is marked as 't', it will not be considered as  
a candidate for video switching (again, for obvious reasons - no video  
on zaptel connections).

So what would probably need to be done is define another dialplan  
flag, that would make appconference initialize a DSP engine for that  
member. It would be similar to 't', but due to backwards compatibility  
issues, we cannot really use 't' for this purpose.  Once that is done,  
appconference _should_ be aware of voice activity from members that do  
not do DTX and _should_ be able to include this information in the VAD- 
based video switching logic.  It will obviously need to be tested and  
there is a good chance that some other parts of the code will need to  
be tweaked.

Hope this helps.  Let me know if you have any questions.  I have also  
copied the appconference dev list on this, and I suggest that we move  
this discussion there, since it is appconference-specific and doesn't  
really relate to asterisk video in general.

Mihai

On May 15, 2008, at 6:48 AM, Borja SIXTO wrote:

> Hi Mihai,
>
> For the 3G handsets we cannot configure this mode for example (Some
> phones generate always an audio stream).
> So I think it will be great to be able to enable the full VAD with a
> specific application option.
> I will read again the source code.
>
> Thanks,
>
>
> Tech from i6net
>
>
> Mihai Balea a écrit :
>>
>> On May 15, 2008, at 3:53 AM, Borja SIXTO wrote:
>>>
>>> The voice conference works well, but I didn't able to use the video
>>> switching based on VAD or DTMF.
>>
>> Just a quick note here, since this is one of the more confusing
>> aspects of appconference:
>> To get VAD-based video switching  working, your clients need to use
>> DTX (i.e. stop sending audio packets when there is no voice
>> activity).  While it is possible to implement a full VAD solution in
>> appconference (the relevant code is there), VAD is quite
>> CPU-intensive, so there are advantages to offloading this to the  
>> clients.
>>
>> Mihai
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