Encoding Discussion Megathread (ffmpeg, Handbrake, AV1, etc...)

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Back to an old discussion @TheDreadPirate and I had regarding auto-cropping (if you trust cropdetect at all). I snagged some awk from somewhere and another person offered an expansion that sorts all results from a sample size of your choice and selects the one which occurs most often in cropdetect output. Pretty cool, actually!

Code:

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In my experience, past black screens and REALLY dark scenes, this is a thoroughly accurate way to crop out black bars. Then you would use this variable in your filter:

Code:

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Make sure to crop prior to other hardware-based filters (e.g., vpp_qsv) or you'll need to use hwdownload and figure out formats. Easier just to crop from the start.

Okay, so using the crop filter with ANY hw-based filters doesn't seem to work at all. However, you can utilize vpp_qsv to the same effect with a tiny bit of extra work (which I've already done):

Code:

cropval=$(jffmpeg -ss 120 -i "${i}" -t 5:00 -filter:v fps=1/2,cropdetect -f null - 2>&1 | awk '/crop/ { print $NF }' | tr ' ' '\n' | sort | uniq -c | sort -n | tail -1 | awk '{ print $NF }') && \
cw=$(echo "${cropval#*crop=}" | cut -d : -f 1) && ch=$(echo "${cropval#*crop=}" | cut -d : -f 2) && \
cx=$(echo "${cropval#*crop=}" | cut -d : -f 3) && cy=$(echo "${cropval#*crop=}" | cut -d : -f 4) && \

And then your vpp_qsv filter would look like this:

Code:

-filter:v "hwupload=extra_hw_frames=64,vpp_qsv=cw=$cw:ch=$ch:cx=$cx:cy=$cy:denoise=6"

Of course with hwupload and denoise optional, just copy/pasted from my script. If scaling, you have to use a separate filter (e.g., scale_qsv) as it doesn't seem to respect scale_mode, w, and h parameters when using crop functions.