Handbrake and Apple VideoToolbox

Feb 6
by shogun
Handbrake VideoToolbox

If you want to take advantage of Macintosh hardware encoder in Handbrake then people have recommended VideoToolbox.  I have been using an M1 Mac Mini to compress blu-ray mkvs using x265 10bit taking two to four hours to encode.

I posed some questions on Handbrakes forums for using VideoToolbox to encode.

"what if any are the quality differences between x265 10bit and VideoToolbox 10bit or anything I need to be aware of?
why wouldn't all Mac users use VideoToolbox?
is there a reason why there are no presets made for VideoToolbox?"

I did not get much help.

this document about Videotoolbox doesn't discuss quality.

this document discusses quality and performance, but does not include VideoToolbox.

There seems to be discrepancies in Handbrakes VideoToolbox quality setting.  x264/5 show RF for the quality slider, but VideoToolbox shows CQ for the quality slider.
Both use the same help text when you hover over the slider and VideoToolbox references RF.  Also the lower the number for RF the high the quality, but it seems for VideoToolbox the higher the number the higher the quality.  Not sure why.
x264/5 has the center of the slider at 20 RF.
Where as VideoToolbox has the center of the slider at 50 CQ.  Does this mean 50 CQ equals 20RF?  No, I don't think so.

For reference, the original test file size is 33.19GB with an overall bitrate of 34.3 Mb/s.

A little encoding testing with Videotoolbox 10bit with preset set to quality:
CQ 19/20 were 5.33GB with 5503kb/s - smaller than X265 RF 20.  mostly looked perfect except two moments of blockiness/smearing.
CQ 35 5.86GB with 6052kb/s - about same size as X265 RF 20 - one scene good, haven't checked other scene yet.
CQ 50 8.56GB with 8849kb/s - much larger
all took 12min at 250fps.  increasing quality did not slow down encode.

I am not sure how much difference the two presets VideoToolbox has, other than the obvious names of speed and quality, there seems to be no documentation that I could find.  Whereas x264/5 has nine settings from ultrafast to veryslow (ten if you include placebo) and is well documented.

VideoToolbox 10bit is way faster than x265 10bit, x265 takes 2 to 4hrs to encode and so far VideoToolbox has taken 12min.

I wish Handbrakes site had more detailed help for VideoToolbox.

Have you tried VideoToolbox in Handbrake and what settings and speeds are you getting?

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