refactore: Implement marker bit validation with debug output in user data parsing.

[AhmedAlian7]

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SCTE 20 Marker Bit Syntax Check

closes #2112

I have implemented a syntax check for the SCTE 20 marker bit in es_userdata.c. This ensures that the parser verifies the marker bit is '1' as per the standard, and logs a debug warning if it is not.

Changes

src/lib_ccx/es_userdata.c

I replaced the TODO comment with a check that reads the bit and logs a warning if it is 0.

// Before
read_bits(ustream, 1); // TODO: Add syntax check

// After
if(read_bits(ustream, 1) == 0)
{
    dbg_print(CCX_DMT_VERBOSE, "SCTE 20: Marker bit is 0 (should be 1)\n");
}

Verification Results

Automated Verification

• Compilation: Successfully compiled es_userdata.c with gcc to ensure no syntax errors were introduced.
• Log Logic: Reviewed the code to ensure dbg_print is used correctly with CCX_DMT_VERBOSE level, which is consistent with other debug prints in the file.

[AhmedAlian7]

@cfsmp3, plz review this one.

[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 6f7ce27...:

Report Name	Tests Passed
Broken	13/13
CEA-708	14/14
DVB	6/7
DVD	3/3
DVR-MS	2/2
General	25/27
Hardsubx	1/1
Hauppage	3/3
MP4	3/3
NoCC	10/10
Options	81/86
Teletext	21/21
WTV	13/13
XDS	34/34

Your PR breaks these cases:

• ccextractor --autoprogram --out=srt --latin1 --quant 0 85271be4d2...
• ccextractor --autoprogram --out=ttxt --latin1 --ucla dab1c1bd65...
• ccextractor --out=srt --latin1 --autoprogram 29e5ffd34b...
• ccextractor --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9...
• ccextractor --startcreditsnotbefore 1 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9...
• ccextractor --startcreditsnotafter 2 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9...
• ccextractor --startcreditsforatleast 1 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9...
• ccextractor --startcreditsforatmost 2 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9...

Congratulations: Merging this PR would fix the following tests:

• ccextractor --out=spupng c83f765c66..., 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 6f7ce27...:

Report Name	Tests Passed
Broken	13/13
CEA-708	14/14
DVB	6/7
DVD	3/3
DVR-MS	2/2
General	25/27
Hardsubx	1/1
Hauppage	3/3
MP4	3/3
NoCC	10/10
Options	81/86
Teletext	21/21
WTV	13/13
XDS	34/34

Your PR breaks these cases:

• ccextractor --autoprogram --out=srt --latin1 --quant 0 85271be4d2...
• ccextractor --autoprogram --out=ttxt --latin1 --ucla dab1c1bd65...
• ccextractor --out=srt --latin1 --autoprogram 29e5ffd34b...
• ccextractor --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9...
• ccextractor --startcreditsnotbefore 1 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9...
• ccextractor --startcreditsnotafter 2 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9...
• ccextractor --startcreditsforatleast 1 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9...
• ccextractor --startcreditsforatmost 2 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9...

Congratulations: Merging this PR would fix the following tests:

• ccextractor --out=spupng c83f765c66..., 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]

Closing as duplicate of #2130, which addresses the same SCTE-20 marker bit TODO.

#2130 is the better fix because it:

• Fixes both C and Rust code (this PR only fixes C)
• Skips the corrupted block with continue instead of just logging (your version continues processing potentially bad cc_data1/cc_data2)
• Checks the marker bit after the bitsleft validation (correct ordering)

Additionally, this PR has a duplicate CHANGES.TXT entry — it adds "Fix: segmentation fault when using --multiprogram" which already exists in the file.

Thank you for the contribution — the fix idea was correct, just #2130 was more complete.