Re: [payload] [rtcweb] Second WGLC on draft-ietf-payload-flexible-fec-scheme

[Magnus Westerlund <[e-mail]>]

Hi,

I have now reviewed -07. It is not ready yet. A significant issue appear 
to exist around how one recovers CSRC lists or header extensions.

1. Section 4.2.2, Figure 13:

The R and F bits are swapped. To my understanding this figure should use 
R=0 and F=1, i.e. 0 1 in the two first bits.

2. Section 4.2.2, Figure 15:

So when R=1, why is F=1? As neither of the F values apply when R=1, why 
not simply define that F=0, which would result in that the RTP payload 
would be equal to the complete RTP packet being retransmitted?

3. Section 4.2.2, Figure 15:

Why isn't the CSRC list or packet header extension of the retransmitted 
packet included in the figure, they will be there if P or X bits of the 
Retransmission is present? Or are they counted as part of the 
retransmission / repair payload?

4. Section 6.2:

    The repair packet payload consists of the bits that are generated by
    applying the XOR operation on the payloads of the source RTP packets.
    If the payload lengths of the source packets are not equal, each
    shorter packet MUST be padded to the length of the longest packet by
    adding octet 0's at the end.

The repair packet does not appear to protect the source packets packet 
extension or CSRC list. I think what is missing here is the need to be 
explicit that the repair payload will be XOR of the source packets' CSRC 
list, extension header and payload?

The reverse thus need to be explicitly said in the recovery section also.

Cheers

Magnus


Den 2018-03-22 kl. 17:41, skrev Roni Even (A):
>
> Hi,
>
> I would like to start a three week second WGLC on RTP Payload Format 
> for Flexible Forward Error Correction in 
> draft-ietf-payload-flexible-fec-scheme-07 
> <https://tools.ietf.org/html/draft-ietf-payload-flexible-fec-scheme-07>.
>
> The WGLC will end on April 11^th , 2018
>
> Note that the first WGLC was on the 05 version  and the 06,07 are 
> incremental updates.
>
> The slides from the IETF 101 payload session describe the changes see 
> https://datatracker.ietf.org/meeting/101/materials/slides-101-payload-flexible-fec-00 
> .
>
> Please send comments to the payload mailing list.
>
> The double posting is to  notify RTCweb WG that the second  WGLC has 
> started since this document is needed for RTCweb
>
> Roni Even
>
> Payload WG co-chair
>
>
>
> _______________________________________________
> rtcweb mailing list
> [e-mail]
> https://www.ietf.org/mailman/listinfo/rtcweb

-- 

Magnus Westerlund

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