Split SDP (string) for m line to change video codecs

manpreet Best Answer 2 years ago

I want to have a method at the end that can set VP9 or H.264 as preferred video codec in a SDP.

So I am looking for the m line in my SDP:

m=video 9 UDP/TLS/RTP/SAVPF 96 98 100 102 127 97 99 101 125

Console log of my SDP:

In this case I would get and use VP8 (96) as video codec instead of VP9 (98). So I want to check if 98/VP9 is possible/available and want to set it at the beginning/first position to actually use it.

What I got so far:

if(sdpOrigin == 'local') {
    let lines = sdp.split('\n').map(l => l.trim());
    lines.forEach(function(line) {
        if (line.indexOf('m=video') === 0) {
            let parts = line.substr(28); // Should be avoided!
            let vp9_order = parts.indexOf("98");
            let array = parts.split(/\s+/);
            console.log("array", array); // 96 98 100 102 127 97 99 101 125
            if (vp9_order > 0) {
                array.splice(vp9_order, 1);
                array.unshift("98");
            }
            console.log("array-new", array); // 98 96 100 102 127 97 99 101 125

            // How do I update my SDP now with the new codec order?

        }
    })
}

This approach is bad in my opinion, because I get my desired m line but I do a fix substring at the position '28', so it will break if something before changes.

At the end I should have the following "m line" in my SDP:

m=video 9 UDP/TLS/RTP/SAVPF 98 96 100 102 127 97 99 101 125

Can somebody help me with that?