WebRTC Chrome 48 VP9 preference

Question

I wish to test VP9 as I understand it is now optional on Chrome 48.

What I have read so far, while inconsistent, seems to imply:

• no flag is needed anymore
• default is to VP8
• to prefer VP9 over VP8, the video codec list in the SDP sent with offer must be reordered to position VP9 as the first entry in the m record

If this is correct can someone please advise how to edit and then read to verify the SDP to achieve this reordering (i.e. VP9 first in the list)?

Answer 1

After some reading and experimentation I was able to edit the SDP video codec preferred list by reordering the m= video entry from a list that begins "100 101" to "101 100" using javascript replace - sdp.replace(/SAVPF 100 101/g, "SAVPF 101 100"); - I then verified that VP9 was active with webrtc internals and also that the visual results were good - the only downside is that cpu utilization increases about 30% so make sure you have the headroom to avoid heat buildup