[CaYatur]

What

A twelfth export format, MP4 — H.265 10-bit (H.265 Main 10, yuv420p10le, BT.709 and hvc1 tags). It is opt-in: existing formats, profiles and their ffmpeg arguments are unchanged.

Why

Dark, smooth gradients band in 8-bit: the YUV conversion and the compression turn them into flat steps. The picture is still drawn in 8-bit RGBA, so 10-bit does not remove steps already in the drawing; it stops the encoder adding more.

How

• depth: 10 on the format; videoArgs adds -profile:v main10 and yuv420p10le (x265) or p010le (NVENC, Quick Sync).
• ffmpeg's AMF encoder takes no 10-bit input, so AMF is not offered for this format (tenBit flag on the encoder table).
• 10-bit is probed with its own key (hevc_nvenc@10) and the real 10-bit arguments, since a GPU can encode 8-bit and not 10-bit. pickEncoder and available look the key up themselves; the capabilities list uses it too.
• takesYuv420 is false for this format, so frames go as RGBA, not through the GPU's 8-bit I420 path.

Measured

Dark gradient scene, 1080p30, 4 s, PSNR against the raw RGBA frames the renderer sent (16-bit RGB, no dithering):

	size	PSNR
x265 8-bit	560 kB	48.35 dB
x265 10-bit	553 kB	49.87 dB
NVENC 8-bit	740 kB	49.42 dB
NVENC 10-bit	710 kB	51.20 dB

A contrast-stretched crop shows large flat blocks in the 8-bit file; the 10-bit one follows the gradient. ffprobe: Main 10, yuv420p10le, bt709 primaries, transfer, matrix and range for both encoders. Speed: about 1.6× the 8-bit time (RGBA instead of I420). Quick Sync could not be checked on this machine; it is offered only where its own 10-bit test encode passes.

Tests

Four new tests: arguments per encoder, no I420 path, AMF excluded and separate probe keys, encoder choice following the 10-bit probe. npm test: 3577/3577.

[cayadraft]

@CaYatur

CaYaDraft — pull request

Summary
This pull request adds a new export format, "MP4 — H.265 10-bit," designed to reduce banding in dark gradients by encoding video at 10-bit depth instead of the standard 8-bit. The implementation introduces specific probe keys and arguments for both x265 and NVENC encoders to support this format while excluding AMF, which does not handle 10-bit input.

Files

• CHANGELOG.md (updated version history)
• README.md & README.tr.md (minor text changes)
• ROADMAP.md (test count update)
• src/main/main.js (encoder probing logic for 10-bit)
• src/shared/export-formats.js (format definitions and probe keys)
• src/shared/i18n.js (new format label)
• tests/export-formats.test.js (added tests for 10-bit support)

Note
Nothing blocking is visible from the text.

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