L64105 LSI Logic Corporation, L64105 Datasheet - Page 238

• Manufacturer Part Number: L64105
• Description: Mpeg-2 Audio/video Decoder
• Manufacturer: LSI Logic Corporation

Figure 7.6
Word 89
Word 90
7.6.3 Normal Mode
7-10
Word 0
Word 1
0
Cb356
Cb0
Cb4
Cb0
Chroma Frame Store Organization
Cr356
Cr0
Cr4
Cr0
number of chroma lines in 4:2:0 source data. Hence, the chroma frame
store requires only half the area of the luma frame store. The three
operating modes and the area consumed is described below.
The normal operating mode of the decoder requires two frame stores for
decoding two anchor frames (I and P pictures) and one frame store for
decoding and storing B pictures. The frame store size is computed using
the following equation:
Equation 7.1
Using NTSC images as an example yields the following:
Equation 7.2
Memory Interface
Cb357
Cb1
Cb5
Cb1
NTSC Chroma
Total Frame Store Size
NTSC Luna
Chroma Frame Store Memory
Luma Frame Store Memory
Cr357
Cr1
Cr5
Cr1
Frame Store Size Calculation (Bytes)
Frame Store Size Example for NTSC:
=
Cb358
Cb2
Cb6
Cb2
720 480
=
720
Cr358
Cr2
Cr6
Cr2
=
480 2
=
3 720 480 1.5
345,600 bytes
Cb359
=
Cb3
Cb7
Cb3
Pixel Width
=
=
Pixel Width
172,800 bytes
Cr359
Cr3
Cr7
Cr3
63
Line Height
Line 1
Line 3
=
1,555,200 bytes
Line Height 2