Re: [webrtc-pc] Missing specification on how to assign bandwidth between encodings and/or drop simulcast layers (#2141)

For example imagine that you have the following encoding settings:

- rid: a minBitrate:700 weight:4 dropOrder=1
- rid: b minBitrate:300 weight:2 dropOrder=2
- rid: c minBitrate:100 weight:1 dropOrder=3

Now, let's say that the BWE is of 2048kbps and that only this video track is present. Then the total weight of the encodings would be 7 and each rid will get the following bandwidths:

- rid a bw=(2048/7)*4=1170
- rid b bw=(2048/7)*2= 585
- rid c bw=(2048/7)*1= 293

If bw dropped to 1024kbps then each layer would get

- rid a bw=(1024/7)*4=585
- rid b bw=(1024/7)*2= 293
- rid c bw=(1024/7)*1= 146

In this case none of the layers will be able to achieve the minimum layer, so the one with lower dropOrder will be dropped and the total weight recalculated and individual layer bw:

- rid b bw=(1024/3)*2= 682
- rid c bw=(1024/3)*1= 342






-- 
GitHub Notification of comment by murillo128
Please view or discuss this issue at https://github.com/w3c/webrtc-pc/issues/2141#issuecomment-475983107 using your GitHub account