implement mfra container and nested tfra and mfro boxes #98

bradh · 2026-01-10T02:53:09Z

See ISO/IEC 14496-12:2022 Section 8.8

coderabbitai · 2026-01-10T02:56:19Z

Walkthrough

This change introduces support for Movie Fragment Random Access (MFRA) box structures in the ISO BMFF format. New modules are added for mfra, mfro, and tfra atoms with complete encoding and decoding implementations. The Mfra struct contains a vector of Tfra entries and an Mfro box. The Tfra implementation includes logic for variable-length field encoding and version selection. The Mfro struct stores a parent size field. Three new enum variants (Mfra, Tfra, Mfro) are added to the Any enum. A MAX constant is added to the u24 type. All implementations include unit tests for round-trip encoding and decoding.

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 29.41% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main changes: implementing mfra container with nested tfra and mfro boxes, which matches the comprehensive set of additions across multiple files.
Description check	✅ Passed	The description references the relevant ISO standard (ISO/IEC 14496-12:2022 Section 8.8) that governs the mfra, tfra, and mfro box implementations in the changeset.

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✨ Finishing touches

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Actionable comments posted: 0

🧹 Nitpick comments (1)

src/mfra/tfra.rs (1)

70-95: Minor: Consider renaming parameter for clarity.

The parameter num_bits_minus_one is technically num_bytes_minus_one (values 0-3 map to 1-4 bytes). However, this aligns with how the ISO spec uses "length_size_of_*" fields, so keeping it consistent with the specification terminology is reasonable.

The .expect() on line 89 is safe because determine_required_lengths ensures the value fits within 24 bits before selecting num_bits_minus_one = 2.

📜 Review details

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 65cf2ea and 76be58b.

📒 Files selected for processing (6)

src/any.rs
src/lib.rs
src/mfra/mfro.rs
src/mfra/mod.rs
src/mfra/tfra.rs
src/types.rs

🧰 Additional context used

📓 Path-based instructions (3)

**/*.rs

📄 CodeRabbit inference engine (CLAUDE.md)

**/*.rs: Code must be clippy-clean (cargo clippy --all-targets --all-features -- -D warnings)
Code must be formatted with rustfmt (cargo fmt) and pass formatting checks (cargo fmt -- --check)
Write unit tests inline within modules using #[cfg(test)]

Files:

src/types.rs
src/lib.rs
src/mfra/mfro.rs
src/any.rs
src/mfra/mod.rs
src/mfra/tfra.rs

src/**/*.rs

📄 CodeRabbit inference engine (CLAUDE.md)

src/**/*.rs: Each MP4 atom type must implement the Atom trait with KIND, decode_body(), and encode_body()
Use Header::read_from() to handle large atoms without loading entire contents into memory
All operations should return Result using custom error types defined in error.rs
Use the custom Buf/BufMut traits for contiguous byte slices instead of ad-hoc buffer handling

Files:

src/types.rs
src/lib.rs
src/mfra/mfro.rs
src/any.rs
src/mfra/mod.rs
src/mfra/tfra.rs

src/any.rs

📄 CodeRabbit inference engine (CLAUDE.md)

Register new atom types in the Any enum (src/any.rs) to enable flexible decoding

Files:

src/any.rs

🧠 Learnings (6)

📓 Common learnings

Learnt from: CR
Repo: kixelated/mp4-atom PR: 0
File: CLAUDE.md:0-0
Timestamp: 2025-08-31T04:06:57.364Z
Learning: Applies to src/moov/** : Place movie metadata atom implementations under src/moov/ (and its hierarchy: trak/mdia/minf/stbl/stsd)

Learnt from: CR
Repo: kixelated/mp4-atom PR: 0
File: CLAUDE.md:0-0
Timestamp: 2025-08-31T04:06:57.364Z
Learning: Applies to src/**/*.rs : Each MP4 atom type must implement the Atom trait with KIND, decode_body(), and encode_body()

Learnt from: CR
Repo: kixelated/mp4-atom PR: 0
File: CLAUDE.md:0-0
Timestamp: 2025-08-31T04:06:57.364Z
Learning: Applies to src/moof/** : Place movie fragment atom implementations under src/moof/

Learnt from: CR
Repo: kixelated/mp4-atom PR: 0
File: CLAUDE.md:0-0
Timestamp: 2025-08-31T04:06:57.364Z
Learning: Applies to src/any.rs : Register new atom types in the Any enum (src/any.rs) to enable flexible decoding

Learnt from: CR
Repo: kixelated/mp4-atom PR: 0
File: CLAUDE.md:0-0
Timestamp: 2025-08-31T04:06:57.364Z
Learning: Place top-level atoms (e.g., ftyp, mdat, free) at the top-level of src/