Comment by nyanpasu64

On my Ivy Bridge laptop running Linux, enabling hardware video decode in mpv took installing one package and adding one line to mpv.conf. Enabling hardware decoding in Firefox took multiple attempts of Googling frantically, toggling flags in about:config, passing logging environment variables to Firefox, recording a Pernosco trace of multi-process communication, and even asking for help in the gfx-firefox Matrix chat where they pointed out I had disabled media.rdd-process.enabled causing Firefox to print a misleading error message in about:support saying HARDWARE_VIDEO_DECODING was available, but failing at runtime saying WebRender was disabled even though it was enabled. And to my knowledge, hardware decoding in Chromium is simply not possible on Linux right now (maybe possible on Chromebooks, I haven't checked).

Even after I fixed hardware acceleration, playing a 1080p YouTube video in Firefox using hardware H.264 decoding took more CPU energy (40% of a core) than playing the same video in mpv using software H.264 decoding (20% of a core). Web browsers are just horrifically complex, intractable to understand, and inefficient.