[FIX ]Captions fail to extract on HEVC video stream #1690

[trufio465-bot]

[FIX]

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This PR fixes an issue where CCExtractor failed to extract EIA-608 captions from HEVC (H.265) transport streams.

Problem:
CCExtractor's transport stream parser did not recognize HEVC (stream type 0x24) as a valid video stream type capable of carrying embedded captions. This resulted in "No captions were found in input" for HEVC files, even when captions were present and playable in other media players.

Solution:
Comprehensive HEVC support has been added across the codebase:

1. Defined CCX_STREAM_TYPE_VIDEO_HEVC (0x24) and CCX_HEVC buffer type.
2. Updated the TS parser to recognize HEVC streams during PMT processing and caption detection.
3. Integrated HEVC streams into the existing AVC (H.264) caption processing pipeline, as both use similar SEI mechanisms for caption embedding.
4. Ensured HEVC streams are correctly handled in stream information, buffer management, and sequencing logic.
5. Updated Rust bindings for consistency.

Impact:
CCExtractor can now successfully detect and extract EIA-608 captions from HEVC transport stream files.

[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 a34ba0f...:

Report Name	Tests Passed
Broken	13/13
CEA-708	13/14
DVB	4/7
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	10/13
XDS	34/34

Your PR breaks these cases:

• ccextractor --service 1 --out=txt f17524b53f...

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

• ccextractor --stdout --quiet --no-fontcolor 79a51f3500..., Last passed:

  Never

• ccextractor --stdout --quiet --no-fontcolor 767b546f96..., Last passed:

  Never

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

  Never

• ccextractor --out=srt --latin1 f23a544ba8..., Last passed:

  Never

• ccextractor --out=srt --latin1 10f0f77cf4..., Last passed:

  Test 5993

• ccextractor --out=srt --latin1 df3b4d62d3..., 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]

@trufio465-bot Do you have a sample for this that you can share?

[cfsmp3]

Thank you for working on HEVC support. I've done a deep review and found some issues:

Current Status

• ❌ Has merge conflicts with current master
• ❌ Breaks one CEA-708 test (sample 115) which is unrelated to HEVC
• ⚠️ Master already has partial HEVC support (merged after this PR was created)

What Master Already Has

Since this PR was created, master has gained:

• CCX_STREAM_TYPE_VIDEO_HEVC = 0x24 in the stream type enum
• HEVC handling in get_buffer_type() (returns CCX_H264 to reuse the AVC path)
• PMT parsing for HEVC streams in ts_tables.c
• HEVC description in init_ts()

Valuable Changes That Master May Still Need

Your PR correctly identifies that several functions only check for MPEG2 when they should also check for H.264 and HEVC:

1. ts_info.c:get_video_stream() - Currently only returns PIDs for MPEG2 streams, missing H.264 and HEVC
2. ts_functions.c:copy_payload_to_capbuf() - The "don't ignore if analyzing video" check only exempts MPEG2
3. ts_functions.c:ts_readstream() - Same issue

These could cause problems when --analyze_video_stream is used with H.264/HEVC content.

Suggested Approach

Rather than adding a new CCX_HEVC buffer type, I recommend keeping master's approach of routing HEVC through the CCX_H264 code path (since both use similar SEI mechanisms for caption embedding). The fixes needed are simpler:

1. Update get_video_stream() to include H.264 and HEVC
2. Update copy_payload_to_capbuf() check to include H.264 and HEVC
3. Update ts_readstream() similarly

This avoids adding new enum values and separate handling in process_data() for what is essentially the same processing path.

Questions

1. Do you have an HEVC sample with captions you can share for testing? (Asked previously on Dec 14)
2. Can you investigate why the CEA-708 MPEG-PS test (sample 115) fails with your changes? This file is not HEVC, so the regression suggests an unintended side effect.

Next Steps

If you'd like to continue with this PR:

1. Rebase onto current master
2. Remove the CCX_HEVC buffer type addition (master's CCX_H264 reuse is cleaner)
3. Keep just the 3 function fixes mentioned above
4. Investigate the test regression

Alternatively, I can create a simpler PR with just the needed fixes based on your analysis, and credit you for identifying the issue.

[cfsmp3]

Closing in favor of #1852 which provides a complete fix for issue #1690. Thank you @trufio465-bot for the initial research - it helped identify the key areas that needed modification.