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Opened 3 years ago

Closed 3 years ago

#9577 closed Patch - Bug Fix (fixed)

CEA-708 captions sometimes spontaneously reset

Reported by: Clayton Smith <argilo@…> Owned by: danielk
Priority: minor Milestone: 0.25
Component: MythTV - ATSC Version: 0.24-fixes
Severity: medium Keywords: cea-708
Cc: Ticket locked: no

Description

Sometimes the CEA-708 closed caption decoder resets the caption display spontaneously, making the captions unreadable. Upon investigation, I found that the code which detects reset (RST) and delay cancel (DLC) commands in the parse_cc_service_stream function is incorrect. It should only inspect command bytes, but it actually scans parameter bytes as well. These parameter bytes may coincide with RST and DLC, causing an undesired reset in the former case, or a premature delay cancel in the latter.

To solve this problem, I added code to skip over parameter bytes. The list of commands and their corresponding number of parameter bytes were taken from the CEA-708 specification. I tested the code on a number of shows, and it now correctly skips over parameter bytes (verified with printf debugging), and the spontaneous resets are gone.

Attachments (1)

caption-rst-dlc-fix.patch (1.6 KB) - added by Clayton Smith <argilo@…> 3 years ago.

Download all attachments as: .zip

Change History (4)

Changed 3 years ago by Clayton Smith <argilo@…>

comment:1 Changed 3 years ago by Clayton Smith <argilo@…>

Oops, I meant to set the type to "Patch - Bug Fix".

comment:2 Changed 3 years ago by paulh

  • Type changed from Bug Report to Patch - Bug Fix

comment:3 Changed 3 years ago by Clayton Smith

  • Milestone changed from unknown to 0.25
  • Resolution set to fixed
  • Status changed from new to closed

CEA-708: Fix spontaneous resets. Closes #9577

Signed-off-by: Mark Kendall <mkendall@…>

Changeset: eebd67a1db7d6f30334b4aba908f6d9ee859882b

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