[core] use seq larger than m_RcvBaseSeqNo to update group readablity

[gou4shi1]

Fix the issue memtioned in #1805 (comment)

[gou4shi1]

For example, in this log https://1drv.ms/u/s!AuaosNlJ5ELxjy_WjKk1fnymnYGY?e=s8hn0F
grep 'TsbPd:@60' pr2026.log | grep 'belated' | grep '1770671297' | less result in

13:47:46.759400/SRT:TsbPd:@60 D:SRT.ts: @61711460:tsbpd: PLAYING PACKET seq=1770671297 (belated 75ms)
13:47:46.800792/SRT:TsbPd:@60 D:SRT.ts: @61711460:tsbpd: PLAYING PACKET seq=1770671297 (belated 116ms)
13:47:46.818400/SRT:TsbPd:@60 D:SRT.ts: @61711460:tsbpd: PLAYING PACKET seq=1770671297 (belated 134ms)
...
...
13:47:59.910359/SRT:TsbPd:@60 D:SRT.ts: @61711460:tsbpd: PLAYING PACKET seq=1770671297 (belated 13226ms)
13:47:59.920639/SRT:TsbPd:@60 D:SRT.ts: @61711460:tsbpd: PLAYING PACKET seq=1770671297 (belated 13236ms)
13:47:59.960557/SRT:TsbPd:@60 D:SRT.ts: @61711460:tsbpd: PLAYING PACKET seq=1770671297 (belated 13276ms)

[maxsharabayko]

You are providing the base seqno of the group's reading position to the receiver buffer when reading a packet.
If there is a packet ready to be read, but it is behind the group's base, it is just skipped (and the memory unit is freed).
Then in one call, the buffer can try to read the next packet for a group, instead of reading the first available packet in the buffer (which was already read from another socket), and waiting for another notification for read-readiness.

[gou4shi1]

You are providing the base seqno of the group's reading position to the receiver buffer when reading a packet.
If there is a packet ready to be read, but it is behind the group's base, it is just skipped (and the memory unit is freed).
Then in one call, the buffer can try to read the next packet for a group, instead of reading the first available packet in the buffer (which was already read from another socket), and waiting for another notification for read-readiness.

exactly, if the another socket is disconnected, then this socket (the first ready-to-play packet is smaller than group_base) will never get a chance to make group readable