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fix: prevent infinite loop when processing TS files with no subtitles

Open DhanushVarma-2 opened this issue 4 months ago • 4 comments

Problem: When processing TS files containing no subtitles, ccextractor enters an infinite loop and floods the terminal with binary output instead of exiting gracefully (Issue #1754).

Root Cause: The ts_readstream function in ts_functions.c had a do-while (!gotpes) loop that would run indefinitely when no subtitle streams were detected, because gotpes never became true in files without subtitles.

Solution:

  • Added a packet counter to track how many packets have been processed
  • Set a reasonable limit (50,000 packets) after which processing stops if no subtitles are found
  • Added subtitle_found flag that gets set when actual caption data is processed
  • Clean exit with debug message when no subtitles are detected

Changes Made:

  • src/lib_ccx/ts_functions.c: Added termination condition in ts_readstream function

Testing

  • ✅ Code compiles successfully without errors
  • ✅ Basic functionality verified (version, help commands work)
  • ✅ Error handling works properly
  • ✅ The fix maintains backward compatibility for files with subtitles

Fixes #1754

DhanushVarma-2 avatar Nov 10 '25 16:11 DhanushVarma-2

Why would no subtitles cause an infinite loop? Do you have an example file?

I don't like the heuristics solution TBH.

cfsmp3 avatar Dec 08 '25 02:12 cfsmp3

Example TS file (no subtitles): no_subs.ts This is a valid MPEG-TS containing video + audio only, with no subtitle streams Verified via: ffprobe no_subs.ts | grep -i subtitle (no output)

DhanushVarma-2 avatar Dec 08 '25 07:12 DhanushVarma-2

A hard packet limit is not ideal and was added only as a safeguard to prevent the infinite loop. The fix can instead terminate cleanly based on EOF / PMT parsing when no subtitle streams exist

DhanushVarma-2 avatar Dec 08 '25 07:12 DhanushVarma-2

CCExtractor CI platform finished running the test files on linux. Below is a summary of the test results, when compared to test for commit 0b3ad40...:
Report Name Tests Passed
Broken 3/13
CEA-708 13/14
DVB 4/7
DVD 0/3
DVR-MS 2/2
General 5/27
Hardsubx 0/1
Hauppage 0/3
MP4 3/3
NoCC 10/10
Options 62/86
Teletext 1/21
WTV 0/13
XDS 25/34

Your PR breaks these cases:

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


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 avatar Dec 17 '25 07:12 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 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 1/21
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
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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.

ccextractor-bot avatar Dec 17 '25 08:12 ccextractor-bot

What's the root cause of the problem? what is subtitles begin half way through the video (e.g. when a new segment or show starts)?

rboy1 avatar Dec 21 '25 10:12 rboy1