This patch adds to the CVF depayloader the capability to regroup H.264
fragmented FU-A packets.
After all packets are regrouped, they are added to the "stash" of H.264
NAL units that will be sent as soon as an AVTP packet with M bit set is
found (usually, the last fragment).
Unrecognized fragments (such as first fragment seen, but with no Start
bit set) are discarded - and any NAL units on the "stash" are sent
downstream, as if a SEQNUM discontinuty happened.
This patch introduces the AVTP Compressed Video Format (CVF) depayloader
specified in IEEE 1722-2016 section 8. Currently, this depayloader only
supports H.264 encapsulation described in section 8.5.
Is also worth noting that only single NAL units are handled: aggregated
and fragmented payloads are not handled.
As stated in AVTP CVF payloader patch, AVTP timestamp is used to define
outgoing buffer DTS, while the H264_TIMESTAMP defines outgoing buffer
PTS.
When an AVTP packet is received, the extracted H.264 NAL unit is added to
a "stash" (the out_buffer) of H.264 NAL units. This "stash" is pushed
downstream as single buffer (with NAL units aggregated according to format
used on GStreamer, based on ISO/IEC 14496-15) as soon as we get the AVTP
packet with M bit set.
This patch groups NAL units using a fixed NAL size lenght, sent downstream
on the `codec_data` capability.
The "stash" of NAL units can be prematurely sent downstream if a
discontinuity (a missing SEQNUM) happens.
This patch reuses the infra provided by gstavtpbasedepayload.c.
