GS2961A Datasheet, PDF (65/104 Pages) Gennum Corporation – Ancillary data extraction

4.17 Ancillary Data Detection & Indication
The GS2961A detects ancillary data in both the vertical and horizontal ancillary data
spaces. Status signal outputs Y/1ANC and C/2ANC are provided to indicate the position
of ancillary data in the output data streams. These signals may be selected for output on
the multi-function I/O port pins (STAT[5:0]).
The GS2961A indicates the presence of all types of ancillary data by detecting the 000h,
3FFh, 3FFh (00h, FFh, FFh for 8-bit video) ancillary data preamble.
NOTE: Both 8 and 10-bit ancillary data preambles are detected by the device.
By default (at power up or after system reset) the GS2961A indicates all types of
ancillary data. Up to 5 types of ancillary data can be specifically programmed for
recognition.
For HD video signals, ancillary data may be placed in both the Y and Cb/Cr video data
streams separately. For SD video signals, the ancillary data is multiplexed and combined
into the YCbCr data space.
For 3G signals, ancillary data may be placed in either or both of the virtual interface data
streams. Both data streams are examined for ancillary data.
For a 3G data stream formatted as per Level A mapping:
• The ancillary data is placed in Data Stream 1 first, with overflow into Data Stream 2
• SMPTE 352M packets are duplicated in both data streams
For a 3G data stream formatted as per Level B mapping:
• Each multiplexed data stream forming the 3G signal contains ancillary data
embedded according to SMPTE 291M
• Each multiplexed data stream forming the 3G signal contains SMPTE 352M packets
embedded according to SMPTE 425M
When operating in HD mode, the Y/1ANC signal is HIGH whenever ancillary data is
detected in the Luma data stream, and C/2ANC is HIGH whenever ancillary data is
detected in the Chroma data stream. The signals are asserted HIGH at the start of the
ancillary data preamble, and remain HIGH until after the ancillary data checksum.
When detecting ancillary data in 3G Level A data, the Y/1ANC status output is HIGH
whenever Data Stream 1 ancillary data is detected and the C/2ANC status output is
HIGH whenever Data Stream 2 ancillary data is detected.
When detecting ancillary data in 3G Level B data, the Y/1ANC status output is HIGH
whenever Data Stream 1 ancillary data is detected on either Y or C channels and the
C/2ANC status output is HIGH whenever Data Stream 2 ancillary data is detected on
either Y or C channels.
When operating in SD mode, the Y/1ANC and C/2ANC signals depend on the output
data format. For 20-bit demultiplexed data, the Y/1ANC and C/2ANC signals operate
independently to indicate the first and last ancillary Data Word position in the Luma
and/or Chroma data streams. For 10-bit multiplexed data, the Y/1ANC signal is HIGH
whenever ancillary data is detected, and the C/2ANC signal is always LOW.
When operating in 3G modes, the Y/1ANC and C/2ANC flags are both zero if the 10-bit
multiplexed output format is selected.
GS2961A 3Gb/s, HD, SD SDI Integrated Receiver
Data Sheet
54385 - 2
September 2012
65 of 104