[EtienneLescot]

Refs #585

On macOS, the live preview now decodes 8-bit H.264 in software, like export already does. HEVC and 10-bit stay on VideoToolbox.

Measured (Mac mini M1, from #585)

4K60 preview	VideoToolbox	Software
Dropped frames / 1200	50	1
Seek	254 ms	152 ms

At 120 fps in 4K, VideoToolbox can't keep up. The cost: 0.3 to 0.65 of a core and 3 to 5x more memory.

Not covered

• Battery impact: not measured.
• Scrubbing feel: the maintainer checks it by hand on the Mac before merging.
• No unit test: the backend choice sits inline in the FFI open_with path, not in a pure function. OPENSCREEN_MAC_DECODE=videotoolbox still forces the old path.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes
  • H.264 8-bit YUV420P videos now use software decoding in previews as well as exports, providing consistent decoder selection across both workflows. Other video formats continue to use the existing default, and explicit decoder preferences remain respected.

[coderabbitai]

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Recent review info

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Commits

Reviewing files that changed from the base of the PR and between da6496e and 1762cb5.

Files selected for processing: 1

• crates/compositor/src/pipeline_macos.rs

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Walkthrough

The macOS decoder now selects software decoding by default for H.264 8-bit YUV420P streams in both preview and export. Explicit environment-variable overrides and the baseline-profile rule retain precedence.

Changes: macOS Decoder Selection

Layer / File(s)	Summary
Decoder selection rule crates/compositor/src/pipeline_macos.rs	The DecodeIntent documentation now describes a shared macOS backend for preview and export. Automatic software decoding now applies to H.264 8-bit YUV420P for both intents. Explicit overrides and the baseline-profile rule retain precedence; other eligible streams default to VideoToolbox.

Priority: Normal

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix

Suggested reviewers: songoao25

Merge Risk: Minimal · up to 1762c

No actionable merge-blocking issue is established.

Pre-merge checks: 3 · 2

Failed checks: 2 warnings

Check name	Status	Explanation	Resolution
Description check		The description explains the change, performance measurements, limitations, and testing context. However, it does not follow the required template and omits the Summary, Type of change, Release impact…	Update the description to include every required template section. Add the appropriate checkbox selections, retain the issue reference as "Refs #585", and place the testing details in the Testing section. Mark Screenshots / video as not app…
Docstring Coverage		Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 1 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 3 passed

Check name	Status	Explanation
Title check		The title clearly identifies the main change: using software decoding for 8-bit H.264 preview on macOS. It is concise and specific.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

Full details: Description check

Explanation

The description explains the change, performance measurements, limitations, and testing context. However, it does not follow the required template and omits the Summary, Type of change, Release impact, Desktop impact, Screenshots / video, and Testing sections.

Resolution

Update the description to include every required template section. Add the appropriate checkbox selections, retain the issue reference as "Refs #585", and place the testing details in the Testing section. Mark Screenshots / video as not applicable if no visual change exists.

Finishing Touches: 💡 1

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