GDECEL[15:0] Gemstar Decoding Even Lines,
Address 0x48[7:0]; Address 0x49[7:0]
The 16 bits of the GDECEL[15:0] are interpreted as a collection
of 16 individual line decode enable signals. Each bit refers to a
line of video in an even field. Setting a bit to 1 enables the decoder
block to retrieve Gemstar or closed caption-compatible data on
that particular line. Setting a bit to 0 prevents the decoder from
trying to retrieve data. See Table 241H 74 and Table 24H 75.
To retrieve closed-caption data services on NTSC (Line 284),
GDECEL[11] must be set.
To retrieve closed caption data services on PAL (Line 335),
GDECEL[14] must be set.
The default value of GDECEL[15:0] is 0x0000. This setting
instructs the decoder not to attempt to decode Gemstar or
CCAP data from any line in the even field.
GDECOL[15:0] Gemstar Decoding Odd Lines,
Address 0x4A[7:0]; Address 0x4B[7:0]
The 16 bits of the GDECOL[15:0] form a collection of 16
individual line decode enable signals. See Table 243H 74 and
Table 24H 75.To retrieve closed caption data services on NTSC (Line
21), GDECOL[11] must be set.
To retrieve closed-caption data services on PAL (Line 22),
GDECOL[14] must be set.
The default value of GDEC0L[15:0] is 0x0000. This setting
instructs the decoder not to attempt to decode Gemstar or
CCAP data from any line in the odd field.
GDECAD Gemstar Decode Ancillary Data Format,
Address 0x4C[0]
The decoded data from Gemstar-compatible transmissions
or closed-caption transmission is inserted into the horizontal
blanking period of the respective line of video. A potential
problem can arise if the retrieved data bytes have the value
0x00 or 0xFF. In an ITU-R BT.656-compatible data stream,
these values are reserved and used only to form a
fixed preamble.
The GDECAD bit allows the data to be inserted into the
horizontal blanking period in two ways:
• Insert all data straight into the data stream, even the reserved
values of 0x00 and 0xFF, if they occur. This can violate the
output data format specification ITU-R BT.1364.
• Split all data into nibbles and insert the half-bytes over
double the number of cycles in a 4-bit format.
When GDECAD is 0 (default), the data is split into half-bytes
and inserted.
When GDECAD is 1, the data is output straight in 8-bit format.
ADV7189B
Table 74. NTSC Line Enable Bits and Corresponding Line
Numbering
Line Number
Line[3:0] (ITU-R BT.470) Enable Bit
Comment
0
10
GDECOL[0] Gemstar
1
11
GDECOL[1] Gemstar
2
12
GDECOL[2] Gemstar
3
13
GDECOL[3] Gemstar
4
14
GDECOL[4] Gemstar
5
15
GDECOL[5] Gemstar
6
16
GDECOL[6] Gemstar
7
17
GDECOL[7] Gemstar
8
18
GDECOL[8] Gemstar
9
19
GDECOL[9] Gemstar
10
20
GDECOL[10] Gemstar
11
21
GDECOL[11] Gemstar or
closed caption
12
22
GDECOL[12] Gemstar
13
23
GDECOL[13] Gemstar
14
24
GDECOL[14] Gemstar
15
25
GDECOL[15] Gemstar
0
273 (10)
GDECEL[0] Gemstar
1
274 (11)
GDECEL[1] Gemstar
2
275 (12)
GDECEL[2] Gemstar
3
276 (13)
GDECEL[3] Gemstar
4
277 (14)
GDECEL[4] Gemstar
5
278 (15)
GDECEL[5] Gemstar
6
279 (16)
GDECEL[6] Gemstar
7
280 (17)
GDECEL[7] Gemstar
8
281 (18)
GDECEL[8] Gemstar
9
282 (19)
GDECEL[9] Gemstar
10
283 (20)
GDECEL[10] Gemstar
11
284 (21)
GDECEL[11] Gemstar or
closed caption
12
285 (22)
GDECEL[12] Gemstar
13
286 (23)
GDECEL[13] Gemstar
14
287 (24)
GDECEL[14] Gemstar
15
288 (25)
GDECEL[15] Gemstar
Rev. B | Page 57 of 104