[PR #1923] fix(mp4): Use fixed-width integer types in bswap functions #2723

New Issue

claunia · 2026-01-29T17:23:36Z

claunia commented

2026-01-29 17:23:36 +00:00

Original Pull Request: https://github.com/CCExtractor/ccextractor/pull/1923

State: closed
Merged: Yes

Summary

Changes bswap16 and bswap32 to use int16_t and int32_t instead of short and long
Ensures consistent NAL unit length parsing across Windows and Linux platforms

Problem

On Windows x64, long is 4 bytes (LLP64 model), while on Linux x64 long is 8 bytes (LP64 model). This type size difference in the bswap32 function could cause inconsistent behavior when parsing NAL unit lengths in MP4/MOV files.

When reading NAL lengths with *(long *)&s->data[i]:

Linux x64: Reads 8 bytes from memory
Windows x64: Reads 4 bytes from memory

This could potentially affect timestamp calculations and cause the timing differences observed between Windows and Linux CI tests.

Changes

Function	Before	After
`bswap16`	`short`	`int16_t`
`bswap32`	`long`	`int32_t`

All call sites in process_avc_sample() and process_hevc_sample() updated accordingly.

Test plan

Builds successfully on Linux
Verify Windows CI tests pass (particularly timing-related tests)
Check if tests 37, 136, 226-230 show improved results

🤖 Generated with Claude Code

**Original Pull Request:** https://github.com/CCExtractor/ccextractor/pull/1923 **State:** closed **Merged:** Yes --- ## Summary - Changes `bswap16` and `bswap32` to use `int16_t` and `int32_t` instead of `short` and `long` - Ensures consistent NAL unit length parsing across Windows and Linux platforms ## Problem On Windows x64, `long` is 4 bytes (LLP64 model), while on Linux x64 `long` is 8 bytes (LP64 model). This type size difference in the `bswap32` function could cause inconsistent behavior when parsing NAL unit lengths in MP4/MOV files. When reading NAL lengths with `*(long *)&s->data[i]`: - **Linux x64**: Reads 8 bytes from memory - **Windows x64**: Reads 4 bytes from memory This could potentially affect timestamp calculations and cause the timing differences observed between Windows and Linux CI tests. ## Changes | Function | Before | After | |----------|--------|-------| | `bswap16` | `short` | `int16_t` | | `bswap32` | `long` | `int32_t` | All call sites in `process_avc_sample()` and `process_hevc_sample()` updated accordingly. ## Test plan - [x] Builds successfully on Linux - [ ] Verify Windows CI tests pass (particularly timing-related tests) - [ ] Check if tests 37, 136, 226-230 show improved results 🤖 Generated with [Claude Code](https://claude.com/claude-code)

claunia added the pull-request label 2026-01-29 17:23:36 +00:00

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Reference: starred/ccextractor#2723