Extend TransformableFrameInterface with "packet" subclass?

[alvestrand]

When we are dealing with packets, there is a bunch of metadata that needs to trundle along with it - much of which is described in the various functions on TransformableFrameInterface. It may be good to use this instead of trying to pass byte buffers to the transformer and forward the metadata "elsewhere".

The current subclasses of that interface are TransformableAudioFrameInterface and TransformableVideoRameInterface (and a MockTransformableFrame used for tests). Each of these has subclasses.

We could consider creating a TransformableRtpPacket that encodes the data + metadata of an RTP packet.

We'd have to be able to reconfigure an RtpReceiver to pass TransformableRtpPacket to the transformer; we may be able to just send TransformableRtpPacket into the RtpSender and have it dealt with appropriately, but whether that's the right approach remains to be seen.

Food for thought.