⚡ Optimize parse_mp4 to avoid allocation

[kira1928]

• What:
  • Updated Mp4Container to accept &[u8] via from_slice method by relaxing ContainerReader trait bounds (removed + 'static).
  • Refactored parse_mp4 and get_mp4_sample_detail in src/lib.rs to use from_slice instead of to_vec() + from_bytes().
• Why:
  • parse_mp4 was cloning the entire input file content into a Vec<u8>, causing significant unnecessary memory allocation and copying overhead.
  • For a 50MB file, this change removes ~50MB allocation and copy.
• Measured Improvement:
  • Added tests/perf_benchmark.rs to measure the impact.
  • Baseline (allocation + copy): ~55ms for 50MB data.
  • Optimized (zero-copy): ~134ns (negligible).
  • The optimization effectively eliminates the O(N) allocation cost before parsing begins.

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PR created automatically by Jules for task 8890887406864034663 started by @kira1928

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[gemini-code-assist]

Summary of Changes

Hello @kira1928, 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 significant optimization to the MP4 parsing logic by transitioning from an allocation-heavy approach to a zero-copy method. By allowing the Mp4Container to process data directly from byte slices, the change eliminates substantial memory allocations and data copying, particularly beneficial when handling large MP4 files. This results in a dramatic improvement in parsing performance and a reduced memory footprint.

Highlights

• Zero-copy MP4 parsing: The Mp4Container now supports parsing directly from &[u8] slices, eliminating the need for Vec<u8> allocations and copies during the parsing process.
• Trait bound relaxation: The 'static lifetime bound was removed from the ContainerReader trait implementation for Mp4Container, enabling the use of borrowed data without lifetime constraints.
• Performance gains: parse_mp4 and get_mp4_sample_detail functions were updated to leverage the new zero-copy approach, drastically reducing memory overhead and improving execution speed by avoiding unnecessary data cloning.
• Performance benchmark: A new test tests/perf_benchmark.rs was added to quantitatively demonstrate the significant performance improvement, showing a reduction from ~55ms to ~134ns for processing 50MB of data.

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[gemini-code-assist]

Code Review

This is an excellent pull request that significantly optimizes MP4 parsing by avoiding unnecessary memory allocations. The changes are well-implemented and follow best practices for zero-copy operations in Rust. By removing the 'static lifetime bound and introducing from_slice, you've made the parser more efficient, as demonstrated by the new performance benchmark. The code is clean, and the goal is clearly achieved. I have one minor suggestion to improve the new benchmark test.

[gemini-code-assist]

To avoid running this performance benchmark on every cargo test (which can be slow), it's a good practice to add the #[ignore] attribute. This way, it will only run when explicitly requested with cargo test -- --ignored.

This helps separate long-running performance tests from regular unit tests.

#[test]
#[ignore]