[Asterisk-Dev] Asterisk Codecs Extension

[Alex Volkov]

Asterisk Codecs ExtensionPedro,

I am not entirely sure as far as the video codecs go, but asterisk can certainly pass-thru any codec that it recognizes. You will probably need to add an asterisk constant (#define) for this codec and create mappings to it in RTP/SDP and maybe some other stacks. The constant is only for asterisk to uniquely identify the codec internally. If this is a codec that is not well-defined by RTP/SDP standard, the codec will have to be passed by name in SDP and mapped to a dynamic RTP packet type. So asterisk has to recognize it (through mappings) to be able to pass it.

Cheers!
Alex.
  ----- Original Message ----- 
  From: Pedro Bessa Goncalves 
  To: asterisk-dev at lists.digium.com 
  Sent: Wednesday, April 14, 2004 5:57 AM
  Subject: RE: [Asterisk-Dev] Asterisk Codecs Extension


  Hi Alex, what if the codec I want to add is for video? I noticed H263 is only available in asterisk/formats/. Does that mean H263 is only being coded in client side and being passed-through by *?

  In that case, if I wanted to support the pass-through of a video stream the only thing I would have to do would be changing the SIP header to indicate the new codec name?

   

  Thank you,

  Pedro

   


------------------------------------------------------------------------------

  From: Alex Volkov [mailto:avolkov at bpvn.com] 
  Sent: quarta-feira, 14 de Abril de 2004 8:20
  To: asterisk-dev at lists.digium.com
  Subject: Re: [Asterisk-Dev] Asterisk Codecs Extension

   

  Pedro,

   

  Simply look at any codec code in asterisk/codecs/. I suggest codec_ulaw.c or codec_alaw.c. The bulk of both of these is the necessary interfacing code to make whatever-generic-codec work with asterisk, and the actual conversions from xlaw to PCM and back are simple 2-liner loops. Once you understand the basic structure of an * codec, look at codec_g723_1.c for an example on how to handle a whatever-generic-codec that is an opaque library.

  Model your new * codec on those, as I think those provide the best examples of an adaptation/abstraction layer.

   

  Cheers!

  Alex.

    ----- Original Message ----- 

    From: Pedro Bessa Goncalves 

    To: Asterisk-Dev at Lists. Digium. Com (asterisk-dev at lists.digium.com) 

    Sent: Tuesday, April 13, 2004 7:35 AM

    Subject: [Asterisk-Dev] Asterisk Codecs Extension

     

    Hi, does anyone know the required function headers for extending Asterisk codecs? 
    Is there another way to import 3rd party codecs? 

    Thank you, 
    Pedro Goncalves 
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