Notes to Table 7-1

Note 1: xil_convolve is accelerated for 3 x 3, 5 x 5, and 7 x 7 kernels.

Note 2: xil_decompress is accelerated for the following cases:

• xil_decompress + color_convert (JPEG compressed image or sequence and MPEG1 compressed sequence)

• xil_decompress + color_convert + display (JPEG compressed image or sequence and MPEG1 compressed sequence)

• xil_decompress + color_convert + scale + display (MPEG1 compressed sequence)

This decoder adheres to full-precision 24-bit CCIR 601 YCC to RGB709 color space conversion.

There are a few instances when decompression of streams will not be accelerated.

• Decompression of JPEG or MPEG1 streams which are not in one contiguous buffer in memory is not accelerated. For example, streams split up using xil_cis_put_bits_ptr might not be accelerated.

• If one frame in a stream is not accelerated for some reason (e.g. the decompressor encountered invalid data in the frame), subsequent frames in the stream will not be accelerated.

• Acceleration is also disabled if one tries to seek backwards or forwards in a stream.

Note 3: xil_rescale + xil_threshold + xil_threshold + display molecule is accelerated using the Creator depth-cueing hardware. However, some restrictions apply, as follows:

• The first threshold must have a high value of 255. The low and map values must be equal (any number N between 0 and 255.)

• The second threshold must have a low value of 0. The high and map values must be equal (any number M between 0 and N).

• The parameters for xil_rescale must be chosen such that y values of the line represented must span the range of values between N and M while the x values are within 0 and 255. See Figure 4-1.

• The images must be 1-banded XIL_BYTE images.

Figure 4-1 Creator Depth-cueing

The following code is an example of a correct call to invoke this molecule:

float scale[1] = 1.5;

float offset[1] = -10;

float t1_lo[1] = 255;

float t1_hi[1] = 240;

float t1_map[1] = 240;

float t2_lo[1] = 0;

float t2_hi[1] = 15;

float t2_map[1] = 15;

xil_rescale(src,tmp1,scale,offset);

xil_threshold(tmp1,tmp2,t1_lo,t1_hi,t1_map);

xil_threshold(tmp2,tmp3,t2_lo,t2_hi,t2_map);

xil_display(tmp3,display);

However, if the same calling sequence is done with scale[1] = .40, the molecule will not be invoked because the line y = 0.40*x -10 only spans the range y = -10 to y = (255*0.40) - 10 = 92 between x = 0 and x = 255. For the molecule to execute, y must span at least the range y = 15 to y = 240 for x between 0 and 255.

Note 4: xil_get_pixel, xil_set_pixel, and xil_tablewarp are accelerated only as display molecules. For xil_tablewarp, only interpolation = "nearest" is accelerated.

Note 5: All the molecules (other than a single xil function + display) that are accelerated are as follows:

• xil_decompress + xil_colorconvert [+ display] ( for JPEG)

• xil_decompress + xil_colorconvert [+ display] ( for MPEG1)

• xil_decompress + xil_colorconvert + xil_scale + display ( for MPEG1)

• xil_threshold + xil_threshold [+ display]

• [xil_rescale] + [xil_threshold] + [xil_threshold] + [xil_cast] + display

• xil_scale + xil_lookup + display (the accelerated molecules are for 8- or 16-bit bilinear scale followed by 8-to-8 bit or 16-to-8 bit lookup)

Note 6: There are some restrictions on the acceleration of xil_affine, xil_scale, and xil_rotate: xil_affine and xil_rotate are accelerated only for 1-, 3-, and 4-banded images with "nearest" interpolation, and only for 1- and 3-banded images with "bilinear" and "bicubic" interpolation. The restriction for xil_scale is that in the case of interpolation = "general" the size of the resampling kernels are limited to 8 x 8 for 8-bit images, and 8 x 4 for 16-bit images.