[asterisk-dev] AST_FRAME_DIGITAL

[Matthew Fredrickson]

Klaus Darilion wrote:
> Matthew Fredrickson wrote:
>> Russell Bryant wrote:
>>> Klaus Darilion wrote:
>>>> What about G3 fax. It is rather the same as 3G video:
>>>>   fax delivers images over a telephone line
>>>>   3G video deliver audio and video over a telephone line
>>>>
>>>> In case of G3 fax, the image data is modulated
>>>> In case of 3G video, the audio/video is multiplexed with H223.
>>>>
>>>> Currently fax is handled inside an application. Taking your argument, 
>>>> the fax decoder should be in the channel driver and deliver 
>>>> AST_FRAME_IMAGE (maybe one per page) to Asterisk's core. But I think the 
>>>> current implementation which is a single application is much better then 
>>>> adding modem functionality to each channel driver.
>>>>
>>>> IMO it is much more flexible only add support for generic data 
>>>> (AST_FRAME_DIGITAL) to channel drivers. Then, new services and features 
>>>> can be added as application without touching the code of channel drivers.
>>> Faxes are passed into Asterisk using the VOICE frame type, indicating that it is
>>> audio.  In the case of T.38, it uses the AST_FRAME_MODEM type.
>> So perhaps we could use our AST_FRAME_MODEM type for this (I'd prefer if 
>> we did this to rename it to something more appropriate, like 
>> AST_FRAME_DIGITAL or something like that), and use subclasses for the 
> 
> So, if I get it right - there is no need to introduce AST_FRAME_DIGITAL 
> as it is already there (but named AST_FRAME_MODEM)?

Yes, basically.  Look in include/frame.h in asterisk 1.4 sources.  There 
are already subclasses defined for T38 and V150.  I'm thinking that an 
extension to this frametype would give us what we want.  Then an 
extension to the translator architecture so that we can make translators 
for frames other than AST_FRAME_VOICE.


-- 
Matthew Fredrickson
Software/Firmware Engineer
Digium, Inc.