feat: add structured parsing sample data support

[alfg]

This pull request introduces structured data decoding for MP4 sample table boxes, making it possible to programmatically access detailed information from boxes like stts, ctts, stsc, stsz, stss, stco, co64, and stsd. It also adds new binaries and examples, including a demonstration of how to analyze and parse sample tables using the new structured output. The changes improve both the API and internal decoders, enabling richer introspection and easier downstream processing of MP4 files.

Structured data support for sample table boxes

• Added a new StructuredData enum and related structs (e.g., SttsData, CttsData, StscData, etc.) to represent parsed box contents in a typed format. Decoders for sample table boxes now return this structured data instead of plain text. (src/registry.rs)
• Updated all relevant box decoders (StsdDecoder, SttsDecoder, CttsDecoder, StscDecoder, StszDecoder, StssDecoder, StcoDecoder, Co64Decoder) to parse their payloads into the corresponding structured types and return them via BoxValue::Structured. (src/registry.rs) [1] [2] [3] [4] [5] [6] [7] [8]
• Modified the API to expose these new structured types and make them available for downstream use. (src/lib.rs, src/api.rs) [1] [2]

Example and binary additions

• Added new binaries (mp4info, mp4samples) and examples (simple, boxes, typed_sample_tables) to Cargo.toml for demonstrating and testing the structured decoding features.
• Implemented an example (examples/typed_sample_tables.rs) that shows how to analyze sample table boxes and access their structured contents, including a demonstration of direct parsing using the registry.

Minor improvements

• Small code style and import tweaks for consistency. (src/api.rs)

[Copilot]

Pull request overview

This pull request adds structured data parsing for MP4 sample table boxes, enabling programmatic access to detailed sample information. However, the implementation has several critical issues that prevent it from working as intended.

Key Changes:

• Added StructuredData enum and related structs to represent parsed MP4 box contents in typed format
• Updated 8 box decoders (stsd, stts, ctts, stsc, stsz, stss, stco, co64) to return structured data
• Added new samples module with API for extracting track sample information
• Added mp4samples binary and typed_sample_tables example to demonstrate the feature

Critical Issues Found:

1. The samples.rs module parses debug strings instead of using the actual BoxValue::Structured data, making it fragile and defeating the purpose of structured parsing
2. Multiple functions return hardcoded placeholder values (track IDs, timescales, file offsets) instead of parsing real data
3. The StsdDecoder doesn't parse version/flags and only processes one entry instead of all entries
4. Test coverage is incomplete - only 3 of 8 decoders are tested

Reviewed changes

Copilot reviewed 7 out of 9 changed files in this pull request and generated 13 comments.

Show a summary per file

File	Description
src/registry.rs	Adds StructuredData types and updates 8 decoders to return structured data; StsdDecoder has incomplete parsing
src/samples.rs	New module for extracting track samples; critically flawed - parses debug strings instead of structured data and returns placeholder values
src/lib.rs	Exports new structured data types and sample extraction API
src/api.rs	Adds handling for BoxValue::Structured in decode_value function
src/bin/mp4dump.rs	Adds structured data formatting support
src/bin/mp4samples.rs	New binary for displaying sample info; uses placeholder values instead of real parsed data
examples/typed_sample_tables.rs	Example demonstrating structured parsing; has unused import
tests/registry_tests.rs	Tests for 3 decoders (stts, stsz, stsc); missing tests for ctts, stss, stco, co64, stsd
Cargo.toml	Declares new binaries (mp4info, mp4samples) and examples

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[Copilot]

Pull request overview

Copilot reviewed 7 out of 10 changed files in this pull request and generated 4 comments.

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[Copilot]

Pull request overview

Copilot reviewed 8 out of 11 changed files in this pull request and generated 10 comments.

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[Copilot]

Pull request overview

Copilot reviewed 8 out of 11 changed files in this pull request and generated 19 comments.

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