Fix/video codecs patching

[dangusev]

1. Fixes publishing codec preferences not being applied, so tracks were still able to use vp8.
   Now, only h264 or av1.

2. Sets "ultrafast" h264 codec preset by default for lowest latency.
   To use the default "medium", pass STREAM_PATCH_AIORTC_H264_PRESET=medium or STREAM_PATCH_AIORTC_H264_PRESET= (empty) env variable.

Summary by CodeRabbit

Release Notes

• New Features

  • H.264 video encoder presets are now configurable through environment variables, defaulting to "ultrafast" for enhanced performance tuning.

• Refactoring

  • Improved codec preference handling timing and encoder initialization for more precise video quality configuration.

• Tests

  • Added test coverage for H.264 preset functionality, including environment variable handling and default value verification.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 1ee843b1-e3ae-49c3-b6d8-09674389dc31

📥 Commits

Reviewing files that changed from the base of the PR and between 5d03f8a and 141cb03.

📒 Files selected for processing (1)

• getstream/video/rtc/encoders_patches.py

📝 Walkthrough

Walkthrough

This PR introduces environment-driven H.264 encoder preset configuration, refactors when codec preferences are applied to video transceivers, updates related documentation and warnings, and adds test coverage for the new preset behavior. The changes affect encoder patching, transceiver management, and video configuration logic.

Changes

Video Encoding Configuration and Management

Layer / File(s)	Summary
H.264 Encoder Preset Configuration and Documentation getstream/video/rtc/encoders_patches.py	Imports av, fractions, and H264_MAX_FRAME_RATE; adds STREAM_H264_PRESET constant from STREAM_PATCH_AIORTC_H264_PRESET environment variable (default "ultrafast"); extends StreamH264Encoder.__init__ to set preset; overrides _encode_frame to lazily create and configure libx264 CodecContext with frame geometry, bitrate, pixel format, framerate, timebase, preset option, and profile; updates patch_sender_encoder docstring and warning message to reference "Stream values" generically.
Codec Preference Application Timing Refactoring getstream/video/rtc/pc.py	Removes codec preference iteration from PublisherPeerConnection constructor and moves it to addTrack() method, applying preferences only when adding sender-backed video tracks by matching the transceiver whose sender equals the returned RTCRtpSender; encoder bitrate patching is now performed within the same track.kind == "video" block, after codec preferences are set.
H.264 Preset Configuration Tests tests/rtc/test_encoders_patches.py	Adds TestStreamH264Preset test suite verifying that STREAM_H264_PRESET and StreamH264Encoder().preset are controlled by the STREAM_PATCH_AIORTC_H264_PRESET environment variable; asserts default "ultrafast" preset, env-driven preset values, and whitespace-stripped parsing after module reload.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Poem

🐰 A preset hops into the encoder's den,
libx264 configs flow like a stream again,
transceivers find their timing, just right,
video tracks dance through the night—
ultrafast by default, no fuss, no flight! 🎥✨

🚥 Pre-merge checks | ✅ 3 | ❌ 2

❌ Failed checks (1 warning, 1 inconclusive)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 40.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.
Title check	❓ Inconclusive	The title 'Fix/video codecs patching' is vague and uses a generic 'Fix/' prefix without clearly specifying what the main changes accomplish.	Consider a more specific title like 'Apply codec preferences for video tracks and set H.264 preset to ultrafast' that conveys the primary changes to reviewers.

✅ Passed checks (3 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/video-codecs-patching

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@getstream/video/rtc/encoders_patches.py`:
- Around line 81-101: H264Encoder._encode_frame currently only sets up
self.codec when it is None, so if the parent reassigns a new CodecContext (e.g.,
on resolution change) your preset/options get lost; update _encode_frame to
detect a freshly-created parent codec (check self.codec is not None and
self.codec.name == "libx264" but self.codec.options.get("preset") != self.preset
or missing expected keys) and re-apply the STREAM_H264_PRESET-related settings
(preset, tune, level and any missing fields like pix_fmt, framerate, time_base,
bit_rate, profile) by merging only missing/incorrect keys into
self.codec.options before calling yield from super()._encode_frame(frame,
force_keyframe) so you preserve parent intent while restoring your latency
optimizations.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 97cd3af5-f2dd-4dda-9b5b-220812d483b5

📥 Commits

Reviewing files that changed from the base of the PR and between 031dc16 and 5d03f8a.

📒 Files selected for processing (3)

• getstream/video/rtc/encoders_patches.py
• getstream/video/rtc/pc.py
• tests/rtc/test_encoders_patches.py