HMP8117_07 Datasheet, PDF (18/45 Pages) Intersil Corporation – NTSC/PAL Video Decoder

HMP8117
PIXEL OUTPUT
Preamble
Data ID
TABLE 7. OUTPUTTING THE SLICED WSS DATA AS BT.656 ANCILLARY DATA
P15
P14
P13
P12
P11
P10
P9
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
P14
ep
1
1
0
0
1
Data Block Number
P14
ep
0
0
0
0
Data Word Count
P14
ep
0
0
0
0
WSS Data
P14
ep
0
0
0
0
P14
ep
0
0
bit 11
bit 10
P14
ep
0
0
bit 7
bit 6
P14
ep
0
0
bit 3
bit 2
WSS CRC
Data
P14
ep
0
P14
ep
0
0
0
0
0
bit 3
bit 2
P14
ep
0
0
0
0
P14
ep
0
0
0
0
CRC
P14
bit 6
bit 5
bit 4
bit 3
bit 2
NOTES:
28. ep = even parity for P8-P13.
29. WSS CRC data = “00 0000” during PAL operation.
30. CRC = Sum of P8-P14 of Data ID through last user data word. Preset to all zeros, carry is ignored.
0
1
bit 13
bit 9
bit 5
bit 1
bit 5
bit 1
0
0
bit 1
P8
0
1
1
0 = odd field data
1 = even field data
1
0
bit 12
bit 8
bit 4
bit 0
bit 4
bit 0
0
0
bit 0
Teletext
The HMP8117 supports ITU-R BT.653 625-line and 525-line
teletext system B, C and D capture. NABTS (North American
Broadcast Teletext Specification) is the same as BT.653
525-line system C, which is also used to transmit Intel
Intercast™ information. WST (World System Teletext) is the
same as BT.653 system B. Figure 16 shows the basic
structure of a video signal that contains teletext data.
The scan lines containing teletext information are monitored.
If teletext is enabled and teletext data is present, the teletext
data is output as BT.656 ancillary data.
DETECTION OF TELETEXT
The teletext decoder monitors the scan lines, looking for the
16-bit clock run-in (sometimes referred to as the clock
synchronization code) used by teletext. If found, it locks to
the clock run-in, the teletext data is sampled and loaded into
shift registers, and the data is then transferred to internal
holding registers.
If the clock run-in is not found, it is assumed the scan line
contains video data unless other VBI information is detected,
such as WSS.
ACCESSING THE TELETEXT DATA
The teletext data must be output as BT.656 ancillary data.
The I²C interface does not have the bandwidth to output
teletext information when needed.
Table 8 illustrates the teletext BT.656 ancillary data format
and Figure 15 depicts the portion of the incoming teletext
signal which is sliced and output as part of the ancillary data
stream. The teletext data is present during the horizontal
blanking interval after the line containing the teletext
information. The actual BT.656 bytes that contain teletext
data only contain 4 bits of the actual data packet. Note that
only the data packet of Figure 16 is sent as ancillary data;
the clock run-in is not included in the data stream.
If a teletext clock run-in is found before line 23 or line 289 for
NTSC and (M) PAL, or line 336 for (B, D, G, H, I, N, N_C) PAL,
the VBI Teletext Detect status bit is immediately set to “1”. If not
found by these lines, the status bit is immediately reset to “0”.
18
FN4643.3
April 19, 2007