[IMPROVEMENT]: Ensure WebVTT output includes minimal X-TIMESTAMP-MAP for HLS compatibility

[AbHash-RixE]

In raising this pull request, I confirm the following (please check boxes):

• I have read and understood the contributors guide.
• I have checked that another pull request for this purpose does not exist.
• I have considered, and confirmed that this submission will be valuable to others.
• I accept that this submission may not be used, and the pull request closed at the will of the maintainer.
• I give this submission freely, and claim no ownership to its content.
• I have mentioned this change in the changelog.

My familiarity with the project is as follows (check one):

• I have never used CCExtractor.
• I have used CCExtractor just a couple of times.
• I absolutely love CCExtractor, but have not contributed previously.
• I am an active contributor to CCExtractor.

SUMMARY

This PR ensures that when --timestamp-map & --out=webvtt is used and no captions are detected, CCExtractor still writes a minimal header containing : X-TIMESTAMP-MAP=MPEGTS:0,LOCAL:00:00:00.000
This makes the generated .vtt file valid for HLS players, which often require this header even in empty subtitle files.

IMPLEMENTATION DETAILS

1. CHANGES.TXT

-Added entry under Unreleased: 1.0
IMPROVEMENT: Add default X-TIMESTAMP-MAP header for empty subtitle files in WebVTT for better compatibility
of HLS streaming (#1743)

2. src/ccextractor.c

-Call webvtt_write_minimal_header() in start_ccx() when no captions are found and --out=webvtt is set.

3. src/lib_ccx/ccx_encoders_helpers.c

-Added new helper function webvtt_write_minimal_header()
-Which:
Initializes encoder context for WebVTT.
Writes a default X-TIMESTAMP-MAP=MPEGTS:0,LOCAL:00:00:00.000 line.
Ensures line terminator respects user config (LF vs CRLF).
Cleans up encoder context properly.

4. src/lib_ccx/ccx_encoders_helpers.h

-Declared the new function: void webvtt_write_minimal_header(void);

[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 3f44115...:

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

All tests passing on the master branch were 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 3f44115...:

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

Congratulations: Merging this PR would fix the following tests:

• ccextractor --autoprogram --out=srt --latin1 f1422b8bfe..., Last passed: Never
• ccextractor --datapid 5603 --autoprogram --out=srt --latin1 --teletext 85c7fc1ad7..., Last passed: Never
• ccextractor --autoprogram --out=ttxt --latin1 c0d2fba8c0..., Last passed: Never
• ccextractor --autoprogram --out=ttxt --latin1 006fdc391a..., Last passed: Never
• ccextractor --autoprogram --out=ttxt --latin1 e92a1d4d2a..., Last passed: Never
• ccextractor --autoprogram --out=ttxt --latin1 7e4ebf7fd7..., Last passed: Never
• ccextractor --autoprogram --out=ttxt --latin1 9256a60e4b..., Last passed: Never
• ccextractor --autoprogram --out=ttxt --latin1 27d7a43dd6..., Last passed: Never
• ccextractor --autoprogram --out=ttxt --latin1 297a44921a..., Last passed: Never
• ccextractor --autoprogram --out=ttxt --latin1 efbe129086..., Last passed: Never
• ccextractor --autoprogram --out=ttxt --latin1 eae0077731..., Last passed: Never
• ccextractor --autoprogram --out=ttxt --latin1 e2e2b501e0..., Last passed: Never
• ccextractor --autoprogram --out=ttxt --latin1 c6407fb294..., Last passed: Never
• ccextractor --autoprogram --out=ttxt --latin1 --datets dcada745de..., Last passed: Never
• ccextractor --autoprogram --out=srt --latin1 --tpage 398 5d5838bde9..., Last passed: Never
• ccextractor --autoprogram --out=srt --latin1 --teletext --tpage 398 3b276ad8bf..., Last passed: Never

All tests passing on the master branch were passed completely.

Check the result page for more info.

[cfsmp3]

This PR has merge conflicts and needs to be rebased against the current master branch.

Please resolve the conflicts and update the PR. The feature itself looks useful for HLS compatibility.

[cfsmp3]

Thank you for working on this HLS compatibility feature! I tested it and found:

Works: Default output filename correctly includes X-TIMESTAMP-MAP=MPEGTS:0,LOCAL:00:00:00.000

Bug: When using -o /path/to/output.vtt, the X-TIMESTAMP-MAP header is NOT written. The webvtt_write_minimal_header() function creates a new encoder context that doesn't use the custom output filename from the command line.

Rebase needed: This PR is 4+ months old and contains unrelated ENABLE_SHARING code from before the share module was removed. Please rebase on current master.

To fix the -o bug, webvtt_write_minimal_header() needs to either:

1. Accept the output filename as a parameter, or
2. Use the existing encoder context instead of creating a new one

[cfsmp3]

Hi @AbHash-RixE, this PR is over 4 months old and has some issues:

1. The -o flag doesn't work correctly
2. Needs rebase on current master

Are you still interested in completing this? If not, we may close it and implement the feature differently.