feat: add get_frames_played_in_range to video decoder hierarchy

[MilkClouds]

Summary

Add get_frames_played_in_range(start_seconds, stop_seconds, fps=None) method to the video decoder hierarchy.

Changes

• BaseVideoDecoder — Add abstract method
• TorchCodecVideoDecoder — Delegate to TorchCodec's native method. Raises NotImplementedError when fps is specified on TorchCodec <=0.10.0 (which doesn't support it)
• PyAVVideoDecoder — Full implementation:
  • fps=None: Seek and decode all frames with pts in [start_seconds, stop_seconds)
  • fps specified: Generate timestamps at 1/fps intervals and delegate to get_frames_played_at
  • Validation matching TorchCodec semantics (start ≤ stop, stream bounds checking)

Tests

• test_pyav_decoder.py — 13 tests added
• test_torchcodec_decoder.py — 6 tests added
• Full video_decoder test suite: 93 passed, 6 xfailed

[gemini-code-assist]

Summary of Changes

Hello @MilkClouds, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a new, flexible method for extracting video frames within a specified time interval, allowing users to retrieve frames either at the video's native frame rate or a custom resampled rate. This enhancement provides a more granular control over frame access, improving the utility of the video decoder hierarchy for various multimedia processing tasks.

Highlights

• New Abstract Method: An abstract method get_frames_played_in_range(start_seconds, stop_seconds, fps=None) has been added to the BaseVideoDecoder class, defining a standard interface for retrieving frames within a specified time range.
• PyAVVideoDecoder Implementation: The PyAVVideoDecoder now fully implements get_frames_played_in_range. It supports decoding frames at the native video rate by seeking and iterating, and also handles fps based resampling by generating timestamps and delegating to get_frames_played_at.
• TorchCodecVideoDecoder Implementation: The TorchCodecVideoDecoder implements get_frames_played_in_range by delegating to TorchCodec's native method. It includes a check to raise NotImplementedError if the fps parameter is used with older TorchCodec versions (<=0.10.0) that do not support it.
• Comprehensive Testing: Extensive tests have been added for both PyAVVideoDecoder (13 new tests) and TorchCodecVideoDecoder (6 new tests) to ensure the correct functionality and error handling of the new get_frames_played_in_range method across various scenarios, including range validation, fps resampling, and edge cases.

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Changelog

• src/mediaref/video_decoder/base.py
  • Added abstract method get_frames_played_in_range to define a common interface for range-based frame retrieval.
  • Included detailed docstrings for the new method, specifying parameters, return types, and potential exceptions.
• src/mediaref/video_decoder/pyav_decoder.py
  • Implemented get_frames_played_in_range to support both native frame rate decoding and fps based resampling.
  • Added robust validation for start_seconds and stop_seconds to ensure they are within valid stream bounds and ordered correctly.
  • Integrated logic to convert av.VideoFrame objects into NCHW NumPy arrays for consistent output.
• src/mediaref/video_decoder/torchcodec_decoder.py
  • Implemented get_frames_played_in_range by delegating to the underlying TorchCodec library's functionality.
  • Added a version compatibility check that raises NotImplementedError if fps is provided to an older TorchCodec version (<=0.10.0).
• tests/video_decoder/test_pyav_decoder.py
  • Added a new test class TestPyAVVideoDecoderGetFramesPlayedInRange with 13 individual tests.
  • Tests cover various scenarios including basic range queries, full video range, single-frame ranges, mid-video ranges, NCHW format verification, empty results for start == stop, and error handling for invalid input parameters.
  • Included tests specifically for fps resampling, verifying correct frame counts for higher fps and native rate behavior when fps=None.
• tests/video_decoder/test_torchcodec_decoder.py
  • Added a new test class TestTorchCodecVideoDecoderGetFramesPlayedInRange with 6 individual tests.
  • Tests validate basic range queries, full video range, NCHW format, error handling for invalid ranges, and the NotImplementedError for fps with older TorchCodec versions.
  • Confirmed that fps=None correctly returns frames at the native rate.

Activity

• The author, MilkClouds, initiated this pull request to introduce a new feature for video frame decoding.
• The PR includes a detailed summary of changes and test results, indicating a thorough approach to development.
• The test suite reports 93 passed tests and 6 xfailed tests, suggesting a comprehensive test coverage with some known, expected failures.

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