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Add --split-dvb-subs to extract each DVB subtitle stream into a separate file (fixes #447) #1836

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Rahul-2k4 wants to merge 7 commits into from
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Add --split-dvb-subs to extract each DVB subtitle stream into a separate file (fixes #447) #1836

Rahul-2k4 wants to merge 7 commits into from

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@Rahul-2k4 Rahul-2k4 commented Dec 17, 2025 •
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Description

This PR adds support for extracting multiple DVB subtitle streams into separate output files via a new opt-in flag: --split-dvb-subs.

It resolves the long-standing request in #447, where users want CCExtractor to automatically handle transport streams containing multiple DVB subtitle tracks (e.g. multi-language broadcasts) without pre-selecting PIDs or running the tool multiple times.

Default behavior is unchanged unless the flag is explicitly enabled.

### Motivation

  • Many DVB transport streams contain more than one subtitle stream (often per language).
  • Currently, CCExtractor extracts only a single stream, which makes multi-language workflows cumbersome.
  • With --split-dvb-subs, CCExtractor:
  • Discovers all DVB subtitle streams via PMT parsing
  • Creates isolated per-PID decoder pipelines
  • Produces one output file per stream (PID or language-suffixed)
  • This makes CCExtractor significantly more convenient for real-world DVB content.

Summary of Changes

  • Added --split-dvb-subs CLI option (disabled by default)
  • Enhanced PMT parsing to discover multiple DVB subtitle streams
  • Refactored DVB subtitle decoder to be instance-safe (no static globals)
  • Introduced per-stream pipelines (decoder + timing + encoder + writer)
  • Implemented PID-based packet routing
  • Added strict option-conflict validation
  • Preserved legacy single-stream behavior

Testing

Built and tested with and without --split-dvb-subs
Verified extraction on DVB TS files containing multiple subtitle streams

Confirmed:

  • One output file per stream
  • Bit-exact legacy behavior when the flag is not used
  • Clean shutdown with proper resource cleanup

Scope / Notes

  • This PR intentionally limits scope to DVB subtitle streams only
  • Teletext multi-stream extraction is not included and can be addressed separately
  • The design is extensible for future language filtering or stream selection

Closing

I’ve tried to keep this change conservative, backward-compatible, and well-isolated from existing logic.
Feedback is very welcome I’m happy to revise or split the PR if needed.

Rahul-2k4 and others added 6 commits December 17, 2025 00:18
@Rahul-2k4
Implement multi-stream DVB subtitle extraction (--split-dvb-subs)
48d633f 
Fixes CCExtractor#447: Extract each DVB stream to a separate file
Initial plan
20421f7
@Rahul-2k4
Fix compiler errors in DVB multi-stream structures
6cd26a6 
- Add missing fields to ccx_decoders_dvb_context: private_data, cfg, initialized_ocr
- Add dvb_decoder_ctx field to ccx_stream_metadata
- Add language field to cap_info structure
- Add split_dvb_subs field to lib_ccx_ctx
- Initialize split_dvb_subs from options in init_libraries
- Fix all references to use correct struct field names (lang vs language, stream_pid vs pid)
- Update Rust bindings to include new language field in cap_info
- Match dvb_init_decoder, dvb_free_decoder, and dvb_decode signatures between header and implementation

Co-authored-by: Rahul-2k4 <[email protected]>
Initial plan
2b4faa7
@Rahul-2k4
Apply clang-format and rustfmt formatting fixes
e1b0271 
Co-authored-by: Rahul-2k4 <[email protected]>
@Rahul-2k4
Merge pull request #7 from Rahul-2k4/copilot/fix-clang-format-issues
eedaf08 
Apply clang-format and rustfmt formatting fixes
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ccextractor-bot commented Dec 17, 2025

CCExtractor CI platform finished running the test files on linux. Below is a summary of the test results, when compared to test for commit f6cb862...:
Report Name Tests Passed
Broken 13/13
CEA-708 14/14
DVB 5/7
DVD 3/3
DVR-MS 2/2
General 27/27
Hardsubx 0/1
Hauppage 3/3
MP4 3/3
NoCC 10/10
Options 75/86
Teletext 3/21
WTV 13/13
XDS 34/34

Your PR breaks these cases:

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

Congratulations: Merging this PR would fix the following tests:

  • ccextractor --out=srt --latin1 --autoprogram 73d9313d64..., Last passed: Never
  • ccextractor --autoprogram --out=ttxt --latin1 --ucla --xds 8e8229b88b..., Last passed: Never
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  • ccextractor --autoprogram --out=srt --latin1 --ucla 7d3f25c32c..., 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
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ccextractor-bot commented Dec 17, 2025

CCExtractor CI platform finished running the test files on windows. Below is a summary of the test results, when compared to test for commit f6cb862...:
Report Name Tests Passed
Broken 12/13
CEA-708 14/14
DVB 5/7
DVD 3/3
DVR-MS 2/2
General 27/27
Hardsubx 0/1
Hauppage 3/3
MP4 3/3
NoCC 10/10
Options 75/86
Teletext 0/21
WTV 13/13
XDS 34/34

Your PR breaks these cases:

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

Congratulations: Merging this PR would fix the following tests:

  • ccextractor --autoprogram --out=ttxt --latin1 --ucla --xds 8e8229b88b..., Last passed: Never
  • ccextractor --autoprogram --out=ttxt --latin1 7236304cfc..., Last passed: Never
  • ccextractor --out=srt --latin1 06b3a9237d..., Last passed: Never
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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.

@Rahul-2k4 Rahul-2k4 deleted the branch CCExtractor:master December 18, 2025 18:40
@Rahul-2k4 Rahul-2k4 closed this Dec 18, 2025
@Rahul-2k4 Rahul-2k4 deleted the master branch December 18, 2025 18:40
@Rahul-2k4 Rahul-2k4 restored the master branch December 18, 2025 18:47
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