Tag HEVC output as hvc1 for all HEVC encoders in ISOBMFF containers

[kazukinakai]

Problem

VideoWriter only sets the hvc1 codec tag for hevc_videotoolbox. ffmpeg defaults HEVC-in-MP4/MOV to the hev1 tag, which is spec-valid but rejected by Apple's AVFoundation — Finder thumbnails, QuickLook, QuickTime Player and Safari all treat hev1-tagged HEVC as unsupported.

So restored output produced with hevc_nvenc (and libx265 / hevc_amf / hevc_qsv) silently fails to preview/play on Apple platforms, while hevc_videotoolbox output works. We hit exactly this: NVENC-encoded restored .mp4 files have no Finder thumbnail and won't QuickLook on macOS.

Fix

Set tag = 'hvc1' for every HEVC encoder when the container is ISOBMFF (.mp4 / .mov / .m4v), not just hevc_videotoolbox:

hevc_encoders = ('libx265', 'hevc_nvenc', 'hevc_amf', 'hevc_qsv', 'hevc_videotoolbox')
if encoder in hevc_encoders and output_path.lower().endswith(('.mp4', '.mov', '.m4v')):
    stream_options['tag'] = 'hvc1'

It's a metadata-only change (no re-encode, no quality/size impact), and non-Apple players accept both hev1 and hvc1.

Note on venue

I see the project's canonical home is Codeberg and GitHub is a mirror — apologies if PRs here aren't your preferred flow. Happy to re-open this on Codeberg; opening here since this is where my fork lives. The patch is a single small diff in lada/utils/video_utils.py and easy to cherry-pick.

[AlvinShenSSW]

Heads up — I tested this change and the hvc1 tag doesn't actually get applied. PyAV/ffmpeg treats stream.options as encoder private options and silently ignores the tag key, so HEVC output in mp4/mov/m4v stays tagged hev1.

Verified on PyAV 16.1.0:

approach	resulting codec_tag_string
stream.options['tag'] = 'hvc1'	hev1
stream.codec_tag = 'hvc1'	hvc1

The tag is the muxer FourCC and needs to be set via video_stream_out.codec_tag = 'hvc1'. I opened #154 with that fix applied to all HEVC encoders (incl. hevc_videotoolbox), which supersedes this one.