L64105 LSI Logic Corporation, L64105 Datasheet - Page 326

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

The horizontal scale and main reads/line values are used for
interpolating the horizontal display size up to the 720 pixels, and should
be updated at the sequence boundary. The pan and scan offset values
are used to display the desired portion of the reconstructed frame store.
Unlike the pan and scan offset values embedded in the bitstream, an
offset value of zero corresponds to the top-left pixel in the reconstructed
frame store image, NOT the center of the image. When under host
control, it is up to the host processor to convert the pan and scan value
to an offset value. Refer to
Figure 9.17
for calculating horizontal pan and
scan offset values. The host can access the bitstream parameters
necessary for calculating the pan and scan offset using the Auxiliary
Data FIFO.
The pan and scan offset values shifts the display image to the right by
( wordOffset x 8 ) + byteOffset pixels. The pan and scan word offset,
Register 280[7:0], corresponds to the horizontal offset in frame memory
words, where one word is equivalent to 8 pixels. The pan and scan byte
offset selects the pixel in the word after the selected word offset. The
Horizontal Size (hs) is the width of the reconstructed frame store
extracted from the sequence header and is used internally for accessing
subsequent lines of the reconstructed image. To enable host-controlled
horizontal pan and scan to 1/8 pixel boundaries, the host should program
the Pan and Scan 1/8 Pixel Offset in Register 279
(page
4-65). This
register changes the start phase of the horizontal interpolation filter and
shifts the image in 1/8 pixel increments. The pan and scan offset values
are sampled at the field boundary giving precise control over the pan and
scan offset timing.
9-34
Video Interface