Recently added filtering out unattached RTX in SetCodecPrefrences.
Turns out it is needed in `getCodecs()` also in the following
scenario
- AddTrack from answer side adds a tracks and has media engine codecs
- An offer is received and negotiated codecs get updated in
media engine. And this does not have one of the codecs added
AddTrack above (default media engine codecs)
- Generate answer will do `getCodecs` which will filter out
the codec missing from the `offer`, but would have let the
corresponding RTX pass through and get added to the answer.
If the MediaEngine contains support for them a SSRC will be generated
appropriately
Co-authored-by: aggresss <aggresss@163.com>
Co-authored-by: Kevin Wang <kevmo314@gmail.com>
Resolves#1989Resolves#1675
Issue:
------
A transceiver's codecs can be modified using `SetCodecPreferences`.
When retrieving codecs from the transceiver after changing codec
preferences of the transceiver (for example changing the SDPFmtpLine),
the filter function was using codec from the media engine. Thus,
the change from `SetCodecPreferences` is lost.
Fix:
----
- When a match is found (either exact or partial), use the codec from
the transceiver instead of media engine.
- Based on feedback, add checks to ensure that PayloadType is not
set incorrectly (i. e. set with a default of 0). If it is set to 0,
use the PayloadType from the media engine, i. e. negotiated value.
Testing:
--------
- Modify SDPFmtpLine of a codec of a transceiver using
`SetCodecPreferences` method of `RTPTransceiver`.
- Invoke `GetParamters` of `RTPREceiver` and ensure that `Codecs`
has the SDPFmtpLine modification. Before this change the change
was not reflected in the returned `Codecs`.
- Check that SDP has payload from codec set via SetCodecPreferences
It isn't possible to send media if a MediaEngine has no codecs. This
catches a common misconfiguration issues that users find themselves in.
Resolves#1702
