Subject: [AVT] Comments on draft-ietf-avt-dsr-es0202050-00.txt

From: Magnus Westerlund <[email-masked]>
Date: Mon, 29 Sep 2003 10:38:10 +0200

Hi Qiaobing & David,

I have a few comments on the draft.

1. Shouldn't VAD be in part of the acronyms list in section 1?

2. Section 2, third paragraph: "In ES 202 050 [1], ETSI issues another 
standard for an Advanced DSR front-end that provides substantially 
improved recognition performance in background noise." Shouldn't the 
last part rather read " ... improved recognition performance when 
background noise is present".

3. Section 2.1, paragraph 2, last sentence: "The front-end supports 
three raw sampling rates: 8 kHz, 11 kHz, and 16 kHz." I think one should 
here point out that the feature frame size is not dependent on the 
number of samples used in each 10 ms sample frame.

4. Section 4.1: "The 4-bit CRC in the FP MUST be calculated using the 
formula defined in 7.2.4 in [1]." A question here, isn't the ETSI 
bit-order in reverse to the normal used in IETF? So are the order in 
which one should feed the CRC algorithm obvious? A small note about this 
may be beneficial.

5. Section 4.1: I think that one should normatively write that any 
number of FPs MAY be aggregate together in a RTP payload and they SHALL 
be consecutive in time. One can also here point out that the RTP payload 
size SHOULD be smaller than MTU to avoid IP fragmentation.

6. Section 4.3: "The RTP header marker bit (M) should be set following 
the general rules defined in [6]." This is slightly lacking, it must be 
at least pointed out that it is the rules for Audio that needs to be 
used and in what section they can be found.

7. Section 5, optional parameters: I think referencing [7] here is going 
a bit to far. I think that copying the parameters into the registration 
is worth the slight size increase.

As the document are in good shape and based on the work on RFC 3557 I 
think that after addressing these comments it is ready for WG LC. If you 
have any comments on this draft please give the authors your comments ASAP.

Cheers

Magnus Westerlund

Multimedia Technologies, Ericsson Research EAB/TVA/A
----------------------------------------------------------------------
Ericsson AB                | Phone +46 8 4048287
Torshamsgatan 23           | Fax   +46 8 7575550
S-164 80 Stockholm, Sweden | mailto: [email-masked]

_______________________________________________
Audio/Video Transport Working Group
[email-masked]
https://www1.ietf.org/mailman/listinfo/avt

---

From: Qiaobing Xie <[email-masked]>
Date: Tue, 30 Sep 2003 14:07:18 -0500

Hi, Magnus,

Thanks for the review and comments. My response in-line.

> 1. Shouldn't VAD be in part of the acronyms list in section 1?

yes.  will add.

> background noise is present".

agreed.

> number of samples used in each 10 ms sample frame.

good point.

> which one should feed the CRC algorithm obvious? A small note about this

I will investigate this further. One thought here is to try to make the
life easier for the gateway function (if present) between the circuit
side and the IP side (this use scenarios is quite likely, IMO), where
when the frame-pair reaches the gateway, the CRC has already been
calculated in ETSI order on the circuit side. So if we can use the same
CRC calculation order, then the gateway would be able to avoid
recalculate the CRC... I will add clarification to this. 

> size SHOULD be smaller than MTU to avoid IP fragmentation.

good point. will clarify.

> used and in what section they can be found.

agreed. will make clearer.

> is worth the slight size increase.

agreed.

> have any comments on this draft please give the authors your comments ASAP.

thanks again.

regards,
-Qiaobing