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);