8-32
Video Decoder Module
The start addresses of frame stores A1, A2, and A3 are programmed by
the host using the registers listed in
Table 8.18
.
8.4.2 Reduced Memory Mode
In RMM, the anchor frames are reconstructed as described in the normal
mode, but the B frame reconstruction uses less than a full frame store.
This mode is used for decoding high-resolution pictures, such as for PAL
(720 x 576), using only 1M x 16 bits of SDRAM.
The host enables RMM by setting the Reduced Memory Mode bit in
Register 248 (
page 4-58
). This register is read by the Video Decoder
only when it encounters an anchor frame (I or P picture). The host
determines the amount of memory allocated to the B frame store by
writing a value into the Number of Segments in RMM field in Register
289 (
page 4-68
). Each segment consists of a frame store for eight lines
of the frame. The minimum and maximum number of segments can be
calculated using the following formulas:
Table 8.18
Frame Store Base Address Registers
Frame Store
Address
1
Register
Page Ref.
A1
Anchor Luma Frame Store 1 Base Address [7:0]
224
4-48
Anchor Luma Frame Store 1 Luma Base Address [15:8]
1
225
Anchor Chroma Frame Store 1 Base Address [7:0]
226
4-48
Anchor Chroma Frame Store 1 Base Address [15:8]
227
A2
Anchor Luma Frame Store 2 Base Address [7:0]
228
4-48
Anchor Luma Frame Store 2 Base Address [15:8]
229
Anchor Chroma Frame Store 2 Base Address [7:0]
230
4-49
Anchor Chroma Frame Store 2 Base Address [15:8]
231
A3
B Luma Frame Store Base Address [7:0]
232
4-49
B Luma Frame Store Base Address [15:8]
233
B Chroma Frame Store Base Address [7:0]
234
4-49
B Chroma Frame Store Base Address [15:8]
235
1. SDRAM addresses at 64-byte boundaries.