Subject: Re: [payload] AD review of draft-ietf-payload-vp8-08

From: Patrik Westin <[email-masked]>
Date: Tue, 21 May 2013 08:22:38 -0700

This is how I think about it

1. Collect all packets with a given RTP timestamp
2. Go through packets in order, sorted by sequence numbers, if packets are
missing, send NACK or decode with missing partitions, see 4.x below.
3. Complete frame is detected by no missing sequence numbers and first
packet in the frame containing S=1 with partId=0 and the last packet in the
frame having the marker bit set.
4.1 scan for the start of a new partition; S=1
4.2 continue scan to detect end of partition; hence a new S=1 (previous
packet was the end of the partition) is found or the marker bit is set, if
a loss it detected before the end of the partition abandon all packets in
this partition and continue the scan repeating 4.1
4.3 store the packets in the complete partition continue the scan repeating
4.1 until end of frame is reached.
4.4 send all complete partitions  to the decoder, if no complete partition
is found discard the whole frame.

Regarding the minor issues:
VP8 only support 8 partitions  hence 3-bits in the PartID field should
therefor be enough.

We have nothing that force the PictureID length to be fixed size during the
session, the receiver must handle both cases so in practice it make no
difference to the receiver. If the sender out of convenience want to keep
the same length it's free to do so.