[Asterisk-video] if2 bit stuffing in app_h324m

[Klaus Darilion]

Francesco Emmi wrote:
> Klaus Darilion wrote:
> 
>>> b243 = buf[31] & (1 << 5)
>>> b244 = buf[31] & (1 << 4)
>> I guess the end should be following (as we start from 0):
>>
>> b242 = buf[31] & (1 << 5)
>> b243 = buf[31] & (1 << 4)
> 
> Sure!
> 
>>> if2[0] = ((b3 b2 b1 b0 )& 0xF0) | (mode & 0x0f) = (REV(buf[1]) & 0xF0) | 
>>>   (mode & 0x0f)
>> Thus, if2 does not use network bit order? Or is it only h324m which does 
>> not use network bit order?
>>
>> Now I know how it is done - but why? Is this somewhere specified in 
>> standard?
>>
>> btw: Why is the mode not bit-reversed? If it is about bit order in 
>> general I would think that "mode" must be reversed too?
> 
> No. Mode must not bit reversed. About standards and reason of bit order 
> I can't answer you. To be honest when dealing with amr stuff we found 
> that it is difficult to retrieve informations from specifications (or at 
> least I had no much time to do it...) and helped ourselves by looking 
> directly h223 dumps coming from 3g mobiles.

btw: what about having dump files which we can analyze with wireshark? I 
know at least that it supports h245 and should also support AMR. But I 
have no clue how to export the data to feed it into wireshark.

regards
klaus