Fix quality issues with SVC screenshares. #1077
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When we munged SDP to set bitrate, it was set on the codec's fmtp line. The codec and its fmtp is shared across media tracks. So if a user is sharing a camera and screenshare tracks, both tracks will be published at the same bitrate (typically the user's camera track). This leads to blurry screenshares. Additionally, screenshares cannot be encoded in VP9 with L3T3_KEY. Chrome degrades quality aggressively whenever L1T3 isn't used.
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size-limit report 📦
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nice findings! |
lukasIO
approved these changes
Mar 15, 2024
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When we munged SDP to set bitrate, it was set on the codec's fmtp line.
The codec and its fmtp is shared across media tracks. So if a user is sharing
a camera and screenshare tracks, both tracks will be published at the
same bitrate (typically the user's camera track). This leads to blurry
screenshares.
Previously this was set because AV1 took a long time to start up. So we are
keeping that behavior only for AV1. I've confirmed that VP9 does not suffer
from the slow-start.
Additionally, screenshares cannot be encoded in SVC with L3T3_KEY. Chrome
degrades quality aggressively whenever L1T3 isn't used.