17-8	Edge-Adaptive Scaling Algorithm	UG-VIPSUITE
			2015.01.23

Compile-time custom coefficients are loaded from a CSV file. One CSV file is specified for vertical coefficients and one for horizontal coefficients. For N taps and P phases, the file must contain N×P values. The values must be listed as N taps in order for phase 0, N taps for phase 1, up to the Nth tap of the Pth phase. You are not required to present these values with each phase on a separate line.

The values must be pre-quantized in the range implied by the number of integer, fraction and sign bits specified in the parameter editor, and have their fraction part multiplied out. The sum of any two coefficients in the same phase must also be in the declared range. For example, if there is 1 integer bit, 7 fraction bits, and a sign bit, each value and the sum of any two values must be in the range [–256, 255] representing the range [–2, 1.9921875].

The bicubic method does not use the preceding steps, but instead obtains weights for each of the four taps to sample a cubic function that runs between tap 1 and tap 2 at a position equal to the phase variable described previously. Consequently, the bicubic coefficients are good for up scaling, but not for down scaling.

If the coefficients are symmetric and provided at compile time, then only half the number of phases are stored. For N taps and P phases, an array, C[P][N], of quantized coefficients is symmetric if for all

and .

That is, phase 1 is phase P–1 with the taps in reverse order, phase 2 is phase P–2 reversed, and so on.

The predefined Lanczos and bicubic coefficient sets satisfy this property. If you select Symmetric for a coefficients set in the Scaler II IP core parameter editor, the coefficients will be forced to be symmetric.

Edge-Adaptive Scaling Algorithm

The edge-adaptive scaling algorithm is almost identical to the polyphase algorithm. It has extensions to detect edges in the input video and uses a different set of scaling coefficients to generate output pixels that lie on detected edges.

In the edge-adaptive mode, each bank of scaling coefficients inside the IP core consists of the following two full coefficient sets:

•A set for pixels that do not lie on the edge—allows you to select a coefficient set with a softer frequency response for the non-edge pixels.

•A set for pixels that lie on the edges—allows you to select a coefficient set with a harsher frequency response for the edge pixels.

These options potentially offer you a more favorable trade-off between blurring and ringing around edges. The Scaler II requires you to select the option to load coefficients at runtime to use the edge-adaptive mode; the core does not support fixed coefficients set at compile time.

Note: Altera recommends that you use Lanczos-2 coefficients for the non-edge coefficients and Lanczos-3 or Lanczos-4 for the edge coefficients.

The Scaler II IP core offers the option to add a post-scaling edge-adaptive sharpening filter to the datapath. You may select this option in any scaling mode, with the exception of the nearest neighbor mode.

Altera Corporation	Scaler II IP Core

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UG-VIPSUITE 2015.01.23

Scaler II Parameter Settings

17-9

•The sharpening filter is primarily for downscale, but you may also use it with upscale. You may enable or disable this functionality at runtime.

•The edge-adaptive sharpening filter attempts to detect blurred edge in the scaling video stream, and applies a sharpening filter where blurred edges are detected.

•The areas that are not detected as blurred edges are left unaltered.

•The blurred edge detection uses upper and lower blur thresholds, which you may alter at compile time or runtime.

•The sharpening engine detects a blurred edge where the difference between neighboring pixels falls between the upper and lower blur thresholds.

•As with the edge threshold for the edge-adaptive scaling, the upper and lower blur threshold values are specified per color plane.

Note: Altera does not recommend you to use this option with nearest-neighbor algorithm because it is of little or no benefit.

Scaler II Parameter Settings

Table 17-2: Scaler II Parameter Settings

	Parameter		Value		Description
	Bits per symbol		4–20, Default = 10		Select the number of bits per color plane.
	Symbols in parallel		1–4, Default = 2		Select the number of color planes sent in
					parallel.
	Symbols in sequence		1–4, Default = 1		Select the number of color planes that are
					sent in sequence.
	Enable run-time control of		On or Off		Turn on to enable run-time control of the
	input/output frame size				image size. If you do not turn on this option,
					the Scaler II IP core does not respond to the
					resolution changes in control packets; and the
					input and output resolutions are set to the
					maximum values you specify.
	Maximum input frame width		32–2600, Default =		Select the maximum width for the input
			1920		frames (in pixels).
	Maximum input frame height		32–2600, Default =		Select the maximum height for the input
			1080		frames (in pixels).
	Maximum output frame width		32–2600, Default =		Select the maximum width for the output
			1920		frames (in pixels).
	Maximum output frame height		32–2600, Default =		Select the maximum height for the output
			1080		frames (in pixels).
	4:2:2 video data		On or Off		• Turn on to use the 4:2:2 data format.
					• Turn off to use the 4:4:4 video format.
Scaler II IP Core						Altera Corporation
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17-10		Scaler II Parameter Settings					UG-VIPSUITE
						2015.01.23
		Parameter			Value		Description
		No blanking in video		On or Off			Turn on if the input video does not contain
							vertical blanking at its point of conversion to
							the Avalon-ST video protocol.
		Scaling algorithm		•	Nearest Neighbor		Select the scaling algorithm.
				•	Bilinear
				•	Bicubic
				•	Polyphase
				•	Edge Adaptive
		Enable post scaling sharpen		On or Off			Turn on to include a post-scaling edge-
							adaptive sharpening filter.
		Always downscale or pass-		On or Off			Turn on if you want the output frame height
		through					to be less than or equal to the input frame
							height, which reduces the size of the line
							buffer by one line.
							If the input height becomes less than the
							specified output height for any reason, the
							output video is undefined but it must still
							have the correct dimensions and the core
							must not crash.
		Share horizontal and vertical		On or Off			Turn on to force the bicubic and polyphase
		coefficients					algorithms to share the same horizontal and
							vertical scaling coefficient data.
		Vertical filter taps		4–64, Default = 8			Select the number of vertical filter taps for the
							bicubic and polyphase algorithms.
		Vertical filter phases		1–256, Default = 16			Select the number of vertical filter phases for
							the bicubic and polyphase algorithms.
		Horizontal filter taps		4–64, Default = 8			Select the number of horizontal filter taps for
							the bicubic and polyphase algorithms.
		Horizontal filter phases		1–256, Default = 16			Select the number of horizontal filter phases
							for the bicubic and polyphase algorithms.
		Default edge threshold		0 to 2bits per symbol–1,			Specify the default value for the edge-adaptive
				Default = 7			scaling mode. This value will be the fixed
							edge threshold value if you do not turn on
							Enable run-time control of input/output
							frame size and edge/blur thresholds.

Altera Corporation	Scaler II IP Core

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UG-VIPSUITE						Scaler II Parameter Settings		17-11
2015.01.23
	Parameter			Value		Description
	Default upper blur limit (per		0 to 2bits per symbol–1,			Specify the default value for the blurred-edge
	color plane)		Default = 15			upper threshold in edge-adaptive sharpening.
						This value will be the fixed edge threshold
						value if you do not turn on Enable run-time
						control of input/output frame size and
						edge/blur thresholds.
	Default lower blur limit (per		0 to 2bits per symbol–1,			Specify the default value for the blurred-edge
	color plane)		Default = 0			lower threshold in edge-adaptive sharpening.
						This value will be the fixed edge threshold
						value if you do not turn on Enable run-time
						control of input/output frame size and
						edge/blur thresholds.
	Vertical coefficients signed		On or Off			Turn on to force the algorithm to use signed
						vertical coefficient data.
	Vertical coefficient integer bits		0–32, Default = 1			Select the number of integer bits for each
						vertical coefficient.
	Vertical coefficient fraction bits		1–32, Default = 7			Select the number of fraction bits for each
						vertical coefficient.
	Horizontal coefficients signed		On or Off			Turn on to force the algorithm to use signed
						horizontal coefficient data.
	Horizontal coefficient integer		0–32, Default = 1			Select the number of integer bits for each
	bits					horizontal coefficient.
	Horizontal coefficient fraction		1–32, Default = 7			Select the number of fraction bits for each
	bits					horizontal coefficient.
	Fractional bits preserved		0–32, Default = 0			Select the number of fractional bits you want
						to preserve between the horizontal and
						vertical filtering.
	Load scaler coefficients at run		On or Off			Turn on to update the scaler coefficient data
	time					at run time.
	Vertical coefficient banks		1–32, Default = 1			Select the number of banks of vertical filter
						coefficients for polyphase algorithms.
	Vertical coefficient function		•	Lanczos_2		Select the function used to generate the
			•	Lanczos_3		vertical scaling coefficients. Select either one
						for the pre-defined Lanczos functions or
			•	Custom
						choose Custom to use the coefficients saved
						in a custom coefficients file.
	Vertical coefficients file		User-specified			When a custom function is selected, you can
						browse for a comma-separated value file
						containing custom coefficients. Key in the
						path for the file that contains these custom
						coefficients.
Scaler II IP Core							Altera Corporation
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