[AVT] Comments on draft-chen-rtp-bv-00.txt

[Magnus Westerlund <magnus.westerlund@ericsson.com>]

Hi,

Here are some comments on this draft. Before this I would like to say 
thank you to the authors for providing a very good initial version of 
the draft. I have very few comments.

1. There is need to tighten up the use of aggregation of consecutive 
frames. I would propose that in section 3.2 and 4.2 add a sentence 
stating that any frames in payload MUST be consecutive. If that is not 
intended there is need for having some mechanism for recovering the 
timestamp for each individual frame.

2. Section 3 and 4 are both missing specification for how to use the 
marker bit. I would suggest the normal definition that for packets with 
there first frame being an speech onset the marker bit is set to 1, 
otherwise 0. Please see draft-ietf-avt-profile-new-13.txt

3. I would also like to see some more text on how one recovers the RTP 
timestamp for an aggregated frame. I now that as long as you only intend 
to aggregate consecutive frames it will be RTP TS + TS_rate*0.005*(n-1) 
however this should be written out.

4. I would also suggest that you tighten the language in Section 5 
regarding that BroadVoice 16 and 32 frames shall not be mixed in a file. 
Please use the suitable RFC 2119 language for this.

5. Section 6.1, the usage of maxptime. Are there any need to define a 
default value for maxptime and especially of selecting 200 ms?

6. Section 6.1, Public Specification. This needs to be a complete 
reference.

7. Section 7. I would suggest that you improve your text for how to map 
the parameters to SDP. I would suggest borrowing text from section 8.3 
of RFC 3267.

8. The reference list needs to be split into normative and informative 
references.


Best Regards


Magnus Westerlund

Multimedia Technologies, Ericsson Research EAB/TVA/A
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Ericsson AB                | Phone +46 8 4048287
Torshamsgatan 23           | Fax   +46 8 7575550
S-164 80 Stockholm, Sweden | mailto: magnus.westerlund@ericsson.com



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