[Asterisk-video] libh324m frame format

[Klaus Darilion]

Ok. But there is still one thing I do not understand:

1. h324m_gw reads from the zap channel
2. It feeds the received frame (h223) into libh324m using H324MSessionRead()
3. It reads demultiplexed frames from libh324m using H324MSessionGetFrame().

4. It converts the h324m frames to ast_frames. If I analyze the h324m 
audio frames retrieved with H324MSessionGetFrame, the frame length is 31 
byte. Thus, this is plain AMR playload withouth ToC.

To make ast_frames with proper ToC I would guess there should be a 
lookup in blockSize[] to find out the corresponding mode instead of 
using framedata[0] (see below code from create_ast_frame) which is not 
the mode but already the plain AMR data.

((unsigned char*)(send->data))[1] = (framedata[0] & 0x78) | 0x04;

regards
klaus

Sergio Garcia wrote:
> libh324m does not do any kind of transcoding, so the amr frame you receive on the app is in if2. 
> 
> Best regards 
> Sergio 
> 
> ---------- Original Message ----------------------------------
> From: Klaus Darilion <klaus.mailinglists at pernau.at>
> Reply-To: Development discussion of video media support in Asterisk<asterisk-video at lists.digium.com>
> Date:  Thu, 26 Jul 2007 09:22:39 +0200
> 
>> Hi Sergio!
>>
>> I have problems to understand the frame format used by libh324m.
>>
>> AFAIK AMR is received from H324M in if2. When app_h324m reads an 
>> libh324m audio frame from libh324m - is the AMR frame still in if2 or is 
>> it converted to if1 inside libh324m?
>>
>> thanks
>> klaus
>>
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