Types of VANC Data
Currently, two types of VANC data can be extracted and written to shared memory pipes for further use.
Closed Captions: CC data embedded in the VANC data as per SMPTE ST 291M if the are written which the specified DID 0x61.
Custom data: Extraction of data within the user defined areas as defined in the SMPTE ST 291M - Type1 DID 0xC0 - 0xCF and Type2 DID 0x50 - 0x5F. The current implementation is limited to the extraction of data based on the NBA Tissot Timer (NTT) protocol by Swiss Timing LTD.
All data is updated once per video unit (field or frame).
Configuration
For the data to be extracted, Matrox.CCExtraction = 1
needs to be set either directly in the configuration file or by setting the value in the Matrox General Section of the Configuration GUI. Additionally, VBI must be enabled on all related input and output channels. As VBI can only be handled from one input, the correct one needs to be selected in the Scene Settings.
Shared Memory Locations
Closed Caption
CC data is stored in five different shared memory keys:
Cea708_String1
Cea708_String2
Cea708_String3
Cea708_String4
Cea708_NumLines
The _String
values hold the closed captions itself and _NumLines
defines how many of those are actually valid.
NTT Data
The valid data is stored in the shared memory key NTT_Message
as plain string and needs to interpreted according to the protocol specification.