HandBrake

There isn't a "Open a folder" option, just a folder and press open. The same way you open a file.

Try a nightly build ( https://handbrake.fr/nightly.php ).

Fixed in https://github.com/HandBrake/HandBrake/ ... 4cdbc6be17

".mp4" must at the end of the filename. Rename your file and put it at the end.

You can send me a private message. I'll check it and then promptly delete it.

A invalid chapter title probably. It would be useful if you could share that sample file.

It means that the HandBrake worker process crashed.

1.4 beta and nightly builds have a "padding" filter to add black bars around the video.

Post the whole build log.

The issue you have with master is probably the Sparkle submodule, look at the HandBrake docs or git docs on how to do a recursive checkout or how to initialise the git submodules.

Which file is missing? The master branch is built automatically on GitHub after each commit, I find I hard to believe a file is missing.
The libtool issue could be related to the VM shared folder.

You aren't dismissing the alert that says that handbrake doesn't support encrypted dvd-video, are you?

It depends on your settings, maybe a filter is not optimised. Post both activity logs.

Set the audio "selection behaviour".

Try to disable b-frames. Probably your player does not know how to handle them properly.

Nightly builds can use a 10bit pipeline if no 8-bit only filter is enabled. Plus, if your HDR movie has got only static metadata, you can get them with mediainfo and manually add them to x265 "additional options" (something like hdr-opt=1:repeat-headers=1:master-display=G(13250,34500)B(750...

Remove /Users/yourusername/Library/Containers/fr.handbrake.HandBrake/Data/Library/Application Support/HandBrake/Queue.hbqueue or download the 1.4 beta.

HDR10 with static metadata is doable, if you use a nightly build and manually set the mastering metadata in x265 additional options textfield.

Your destination folder is not writable.

I think ~ 55 might be a good starting value.
At the present time we expose only the 8-bit hardware encoder. The M1 can do 10-bit hevc too, but there is no ETA on when it will be available in HandBrake.

Hardware encoder quality/bitrate ratio is still worse than a good software encoder.

Yes, constant quality is supported.

Yes, old versions are available on https://handbrake.fr/old.php
Or you could update the iMac to El Capitan and get the latest HandBrake version.

Run

pmset -g

in Terminal while HandBrake is encoding and post the output here.

That's not true, the hardware encoder is supported (if you select it in the encoder popup).
The hardware decoder is not supported and there is no plan to support it.