docs/debug: add verbose log when user data is skipped

[pranavshar223]

[IMPROVEMENT]

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• I accept that this submission may not be used, and the pull request closed at the will of the maintainer.
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---

What this PR does

• Adds clarifying documentation comments to src/rust/src/es/userdata.rs
• Adds verbose debug logging when MPEG user data is skipped due to invalid or empty bitstream

Why this is useful

userdata.rs contains complex legacy parsing logic for multiple caption standards.
The added documentation and logging improve readability and debuggability without
changing runtime behavior.

Scope

• Documentation and debug logging only
• No functional or behavioral changes

[pranavshar223]

Hi maintainers,

It looks like the test_rust CI failure is coming from an existing
type mismatch in src/parser.rs:

[pranavshar223]

My changes are limited to documentation and verbose debug logging in
src/rust/src/es/userdata.rs, and do not touch the parser or Rust test code.

Please let me know if you’d prefer me to:

• leave this PR as-is and wait for the test issue to be resolved upstream, or
• rebase once the Rust test failure is fixed on master.

Thanks!

[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 d494286...:

Report Name	Tests Passed
Broken	13/13
CEA-708	14/14
DVB	6/7
DVD	3/3
DVR-MS	2/2
General	27/27
Hardsubx	1/1
Hauppage	3/3
MP4	3/3
NoCC	10/10
Options	85/86
Teletext	21/21
WTV	13/13
XDS	34/34

Your PR breaks these cases:

• ccextractor --autoprogram --out=srt --latin1 --quant 0 85271be4d2...
• ccextractor --out=spupng c83f765c66...

Congratulations: Merging this PR would fix the following tests:

• ccextractor --autoprogram --out=ttxt --latin1 --ucla dab1c1bd65..., Last passed: Never
• ccextractor --out=srt --latin1 --autoprogram 29e5ffd34b..., Last passed: Never
• ccextractor --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed: Never
• ccextractor --startcreditsnotbefore 1 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed: Never
• ccextractor --startcreditsnotafter 2 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed: Never
• ccextractor --startcreditsforatleast 1 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed: Never
• ccextractor --startcreditsforatmost 2 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed: Never

It seems that not all tests were passed completely. This is an indication that the output of some files is not as expected (but might be according to you).

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 c65fb08...:

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	85/86
Teletext	21/21
WTV	13/13
XDS	34/34

Your PR breaks these cases:

• ccextractor --out=spupng c83f765c66...

Congratulations: Merging this PR would fix the following tests:

• ccextractor --autoprogram --out=srt --latin1 --quant 0 85271be4d2..., Last passed: Never
• ccextractor --autoprogram --out=ttxt --latin1 --ucla dab1c1bd65..., Last passed: Never
• ccextractor --out=srt --latin1 --autoprogram 29e5ffd34b..., Last passed: Never
• ccextractor --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed: Never
• ccextractor --startcreditsnotbefore 1 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed: Never
• ccextractor --startcreditsnotafter 2 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed: Never
• ccextractor --startcreditsforatleast 1 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed: Never
• ccextractor --startcreditsforatmost 2 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed: Never

It seems that not all tests were passed completely. This is an indication that the output of some files is not as expected (but might be according to you).

Check the result page for more info.

[cfsmp3]

The documentation and debug logging changes to userdata.rs look good, but this PR has issues that need to be fixed before merging:

1. Revert linux/pre-build.sh changes

This file should not be modified. The diff shows 34 additions / 34 deletions but the content is identical - this is a CRLF line ending issue from Windows development.

Shell scripts must have LF (Unix) line endings. CRLF will break the script on Linux with "bad interpreter" errors.

Fix: Revert this file to match master, or run:

git checkout master -- linux/pre-build.sh

2. Configure git to handle line endings

To prevent this in future PRs, configure git:

git config --global core.autocrlf input

Or add a .gitattributes entry (already exists in repo - ensure it's working).

3. Clean up commit history (optional but recommended)

The commits "retry the test" and "restore all changes" add noise. Consider squashing into a single clean commit.

---

Once the pre-build.sh changes are reverted, this PR is ready to merge.