radeonsi on 7840U Phoenix - no vaapi hardware decoding for codecs rather than h264 with mesa-git, no issue with 23.3 release.
Noticed high CPU usage of RDD process in Firefox playing youtube, checked about:support - no codecs except h164. Same story in vainfo utility - so firefox detects correctly, same way as vainfo utility. Reverted back to mesa 23.3.0 release - codecs are back, RDD cpu usage normal.
Attachung vainfo output for both mesa-git and mesa 23.3