66 Bug/Enhancement: check_sp_output hangs indefinitely on frozen FFmpeg streams

[abhiTronix]

Brief Description

The check_sp_output function should accept a timeout argument (via kwargs) to prevent indefinite hanging. If the timeout is reached, it should cleanly catch the subprocess.TimeoutExpired exception, terminate the process, flush the remaining buffer, and return the captured output without raising a CalledProcessError.

Requirements / Checklist

• I have read the DeFFcode PR Guidelines.
• I have read the DeFFcode Documentation.
• I have updated the documentation files accordingly(if required).

Related Issue

#66

Context

This PR introduces timeout argument (via kwargs) to prevent indefinite hanging in check_sp_output function

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Miscellaneous (if available):

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📝 Walkthrough

Walkthrough

This PR introduces environment-configurable subprocess timeouts, refactors check_sp_output() to handle timeout expiry by terminating and re-communicating with subprocesses, updates device discovery and metadata probing to use explicit timeouts, modifies pixel-format extraction regex logic, and bumps the version to 0.2.8 alongside documentation updates.

Changes

Subprocess Timeout Support & Device Discovery Enhancement

Layer / File(s)	Summary
Configuration Constants deffcode/ffhelper.py	Added DEFAULT_TIMEOUT_SUBPROCESS (env-driven, default 3.0s) and converted DEFAULT_TIMEOUT to float sourced from environment variables.
Subprocess Timeout Handling deffcode/ffhelper.py	Refactored check_sp_output() to accept optional timeout kwarg; on TimeoutExpired, kills subprocess and re-communicates to retrieve partial output; error handling adapted based on timeout occurrence.
FFmpeg Binary Download deffcode/ffhelper.py	Updated HTTP adapter retry timeout to use DEFAULT_TIMEOUT_SUBPROCESS instead of hardcoded value in download_ffmpeg_binaries().
Device Discovery Integration deffcode/ffhelper.py	Updated extract_device_n_demuxer() to pass timeout=DEFAULT_TIMEOUT_SUBPROCESS to all device-detection check_sp_output() calls; expanded Linux v4l2-ctl failure predicate.
Metadata Probing Integration deffcode/sourcer.py	Imported DEFAULT_TIMEOUT_SUBPROCESS; updated metadata-probing check_sp_output() invocation in __validate_source() to explicitly pass timeout argument; added timeout to device enumeration validation calls.
Pixel Format Extraction Logic deffcode/sourcer.py	Changed __extract_video_pixfmt() regex from Video:-prefix matching to comma-delimited codec/format token matching, altering the source of extracted pixel-format values.
Tests & Versioning tests/test_ffhelper.py, deffcode/version.py	Updated test_check_sp_output() to pass explicit timeout=2.0 argument; incremented version from 0.2.7 to 0.2.8.
Documentation README.md, docs/overrides/main.html	Updated webcam documentation link reference in README "Highly Adaptive" section and reformatted announcement link construction in template.

Possibly Related Issues

• Bug/Enhancement: check_sp_output hangs indefinitely on frozen FFmpeg streams #66: The subprocess timeout refactor with env-driven configuration and timeout-aware exception handling directly addresses subprocess hang and timeout robustness concerns.

Estimated Code Review Effort

🎯 4 (Complex) | ⏱️ ~45 minutes

Poem

🐰 Timeouts tamed with patient care,
Subprocesses caught mid-air,
Enviroment whispers, 3 seconds passed,
Device discovery fast, at last!
From 0.2.7 we leap with grace! ✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: adding configurable subprocess timeouts to prevent check_sp_output from hanging indefinitely on frozen FFmpeg streams.
Docstring Coverage	✅ Passed	Docstring coverage is 91.67% which is sufficient. The required threshold is 80.00%.
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.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch 66-bugenhancement-check_sp_output-hangs-indefinitely-on-frozen-ffmpeg-streams-2

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