Adds `Format::Hevc` (Export > Format > H.265 (HEVC); `"format": "hevc"` in
`file.exportMedia`): HEVC Main, 8-bit 4:2:0, in MP4 (`hvc1`) or QuickTime, with AAC audio,
encoded by the macOS hardware encoder. There is no built-in H.265 encoder (one in pure Rust
is a project of its own, and x265 is GPL), so the format exists only where the OS has one.
- `videotoolbox_encode`: the session wrapper creates HEVC sessions too (`VtProfile::HevcMain`;
the profile also says which codec). Keyframes are the HEVC random access points (NAL types
16 to 21); the parameter sets are VPS / SPS / PPS; the `hvcC` record in the MP4 sample
entry is the one VideoToolbox writes (sample description extension atoms), so profile,
level and flags are the encoder's own. `VtEncoder::uses_hardware()` asks VideoToolbox
whether the session runs on a hardware encoder (a test checks H.264 and HEVC), so a
requirement dropped by accident could never become a silent software encode.
- `hardware_encode`: one adapter for both codecs. Choosing the format is the opt-in (the
`hardware_encoding` setting is for H.264). `hevc_available()` (one small hardware session,
created once) is registered with the new `filmcraft_export::register_format_probe`, so
`available(Format::Hevc)`, the format list of Export mode and `exportFormats` follow the
machine. `Format::has_builtin_encoder` says which formats need such a probe.
- `export`: `Format::is_h26x` where H.264 and H.265 behave alike (MP4 or QuickTime, AAC, size
estimate, summary line). Two-pass VBR is refused up front ("H.265 export has no two-pass
mode") and HDR sequences export as SDR, because there is no encoder to fall back to.
- Export mode: H.265 shows H.264's multiplexer, audio, metadata and bitrate controls, without
profile, level, two-pass or the hardware checkbox, and says "Encoder: Hardware".
Apple M1 (8 cores), 1080p25, a 9:29 timeline (camera clip, ProRes 4444 overlays, AAC,
loudness): hardware H.265 at 10 Mb/s 195 s, hardware H.264 at 20 Mb/s 204 s (CPU 1029 s and
1042 s; the same H.264 export took 193 s and 200 s on other runs). It is not faster: the codec
that compresses further is the more expensive one (raw encoders: 166 and 189 frames/s), and
the export is bound by the CPU compositor, not by the media engine.
Quality per bit, 30 s of the same timeline against a ProRes 422 HQ export (average PSNR over
the three planes, SSIM): 20 Mb/s 46.88 dB / 0.9902 (H.264) and 46.91 dB / 0.9903 (H.265);
10 Mb/s 44.96 / 0.9863 and 45.09 / 0.9863; 6 Mb/s 43.72 / 0.9833 and 44.31 / 0.9843; 4 Mb/s
42.91 / 0.9807 and 43.64 / 0.9825; 3 Mb/s 42.37 / 0.9786 and 43.05 / 0.9807. The same picture
at 10 Mb/s and above; at 3 to 6 Mb/s H.265 needs 22 to 31 % less bitrate for the same PSNR.
Both formats therefore keep the same default bitrate. Details in docs/performance.md (HW3).
Tests: tests/hardware_encode.rs gets the HEVC counterparts of the H.264 ones (what is taken
and declined, a round trip through our HEVC decoder with luma PSNR above 30 dB, keyframes, MP4
and QuickTime exports with AAC, ffmpeg / ffprobe reading `hevc` / `Main` / `hvc1` /
`yuv420p` / BT.709, exact sizes, hostile configurations, encoders dropped at any point, the
format list agreeing with the probe, sessions on the hardware encoder); settings_tests.rs
checks names, ids, defaults, the summary, two-pass refusal and the probe; export_ui.rs the
controls H.265 shows and hides.
Stacked on the hardware H.264 encoder (the first commit of this branch).
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
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