fix(mp4): Use fixed-width integer types in bswap functions

[cfsmp3]

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

[ccextractor-bot]

CCExtractor CI platform finished running the test files on linux. Below is a summary of the test results, when compared to test for commit 63dde6f...:

Report Name	Tests Passed
Broken	13/13
CEA-708	14/14
DVB	7/7
DVD	3/3
DVR-MS	2/2
General	27/27
Hardsubx	1/1
Hauppage	3/3
MP4	3/3
NoCC	10/10
Options	86/86
Teletext	21/21
WTV	13/13
XDS	34/34

All tests passed completely.

Check the result page for more info.

[ccextractor-bot]

CCExtractor CI platform finished running the test files on windows. Below is a summary of the test results, when compared to test for commit 63dde6f...:

Report Name	Tests Passed
Broken	13/13
CEA-708	14/14
DVB	6/7
DVD	3/3
DVR-MS	2/2
General	25/27
Hardsubx	1/1
Hauppage	3/3
MP4	3/3
NoCC	10/10
Options	80/86
Teletext	21/21
WTV	13/13
XDS	34/34

NOTE: The following tests have been failing on the master branch as well as the PR:

• ccextractor --autoprogram --out=srt --latin1 --quant 0 85271be4d2..., Last passed:

  Test 7345

• ccextractor --autoprogram --out=ttxt --latin1 --ucla dab1c1bd65..., Last passed:

  Test 7345

• ccextractor --out=srt --latin1 --autoprogram 29e5ffd34b..., Last passed:

  Test 7345

• ccextractor --out=spupng c83f765c66..., Last passed:

  Test 7345

• ccextractor --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed:

  Test 7345

• ccextractor --startcreditsnotbefore 1 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed:

  Test 7345

• ccextractor --startcreditsnotafter 2 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed:

  Test 7345

• ccextractor --startcreditsforatleast 1 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed:

  Test 7345

• ccextractor --startcreditsforatmost 2 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed:

  Test 7345

This PR does not introduce any new test failures. However, some tests are failing on both master and this PR (see above).

Check the result page for more info.