Unclear pliCount, firCount, and nackCount for outbound-rtp

[k0nserv]

For outbound-rtp, pliCount, nackCount, and firCount in particular, the spec says that the "count" is calculated through some method defined in various RFCs. However those RFCs don't seem to define any such method.

For example, for nackCount the spec says:

Count the total number of Negative ACKnowledgement (NACK) packets sent by this receiver.
Calculated as defined in [RFC4585] section 6.2.1.

However, RFC4584 6.2.1 does not specify anything about calculating this count as far as I can tell.

Please advise

[fippo]

Nice catch!
For PLI and FIR this is simply the count of the RTCP packets with the types defined in those sections.

For NACK it is a bit more complicated since a NACK packet can contain but a base sequence number as well as at least one bitmask describing 16 additional sequence numbers relative to the base one.
this in libwebrtc describes it as number of NACK packets but digging a bit further shows this is incrementing the count for each lost packet.