Subject: RE: [AVT] Question on AMR PL-format: CRC building

From: [email-masked]
Date: Mon, 28 Jan 2002 11:50:16 +0200

hello Tobias,

I agree with you, there should not be CRC bits for NO_DATA frames.
Actually this is already specified in the draft, in section 2.3:

"
   FT (4 bits): Frame type indicator, indicating the AMR or AMR-WB
   speech coding mode or comfort noise (SID) mode. The mapping of
   existing modes to FT is given in Table 1a in [2] for AMR and in Table
   1a in [4] for AMR-WB. If FT=14 (speech lost, available only in AMR-
   WB) or FT=15 (No transmission/no reception) no CRC or payload frame
   is present.
"

br,
Ari

> -----Original Message-----
> From: ext Faerber Tobias ICM MP PO8 RD MCH83
> [mailto:[email-masked]]
> Sent: 28 January, 2002 11:21
> To: AVT WG
> Subject: [AVT] Question on AMR PL-format: CRC building
> 
> 
> In case there is a NO_DATA frame within a RTP payload 
> containing several 
> AMR frames, e.g. (7,7,8,15,15,7), and CRC bits are 
> transmitted, is there 
> a CRC entry for the NO_DATA frames as well? I could not find 
> anything in 
> draft-ietf-avt-rtp-amr-10.txt on this. In my opinion it would 
> make not 
> much sense to send CRC bits for NO_DATA frames, as there is 
> nothing to 
> protect and they would just have to be 0's. From the PT entries you 
> would be able to associate the right CRC bits to the data containing 
> frames. However, this would have to be specified clearly, since it 
> cannot easily be seen from the payload contents which method has been 
> used.
> 
> 
> 
> --------------------------------------------------------------
> --------------
> -------
>  Faerber Tobias		Siemens AG
> --------------------------------------------------------------
> --------------
> -------
> 
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