Re: [xrblock] ops-dir review of draft-ietf-xrblock-rtcp-xr-loss-conceal-10

[Qin Wu <[e-mail]>]

Hi,
In the OPS-DIR review, our reviewer asked to provide the hex value of the default threshold setting and one rounding issue was brought up.
The related paragraph in the draft is:
"
> >    SCS Threshold: 8 bits
> >
> >       The SCS Threshold is defined as the percentage of packets
> >       corresponding to lost or discarded frames that must occur within a
> >       one second period in order for the second to be classified as a
> >       Severely Concealed Second.  This is expressed in numeric format
> >       0:8 and hence can represent a range of 0.1 to 25.5 percent loss or
> >       discard.
> >
> >       A default threshold of 5% effective frame loss (50ms effective
> >       frame loss ) per second is suggested.
"
The SCS threshold is represented in percentage. When we use numeric format 0:8
to represent the default value of SCS threshold, we only can represent 0.05078125
rather than 0.05 or 5% (which is set as the default value of threshold in the draft).

If we change the default threshold value into 0.05078125 and the hex value of 0.05078125 is 0x0D,
This rounding issue can be resolved. 

Alternatively, we can change unit of SCS threshold back into millisecond, we can precisely represent 5% 
frame loss per second or the default threshold value 0.05. The range of 0.1 to 25.5 percentage can be
represented into the range from 1ms effective frame loss to 255ms effective frame loss.

Regards!
-Qin