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Chroma Resampling

Downsample or upsample chrominance components of images

  • Library:
  • Computer Vision Toolbox / Conversions

  • Chroma Resampling block

Description

The Chroma Resampling block resamples the chrominance components of an input image. Chroma resampling consists of these operations:

  • Downsample — Reduces the bandwidth required for transmission or storage of a signal. You can prevent aliasing by applying a lowpass filter to bandlimit the input signal.

  • Upsample — Expands the bandwidth of the signal. This block performs interpolation to approximate the missing chrominance values.

Ports

Input

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Blue-difference chrominance component of the image, specified as an M-by-D matrix. D is half the width of the image.

Data Types: single | double | uint8

Red-difference chrominance component of the image, specified as an M-by-D matrix. D is half the width of the image.

Data Types: single | double | uint8

Output

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Blue-difference chrominance component of image, returned as an M-by-P matrix. P is half the width of the resampled image. If you downsample the input image, P is less than D. If you upsample the input image, P is greater than D.

Data Types: single | double | int8 | uint8

Red-difference chrominance component of image, returned as an M-by-P matrix. P is half the width of the resampled image. If you downsample the input image, P is less than D. If you upsample the input image, P is greater than D

Data Types: single | double | int8 | uint8

Parameters

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Specify the resampling method to use to downsample or upsample the chrominance components of the image.

These options specify downsampling operations:

  • 4:4:4 to 4:2:2

  • 4:4:4 to 4:2:0 (MPEG1)

  • 4:4:4 to 4:2:0 (MPEG2)

  • 4:4:4 to 4:1:1

  • 4:2:2 to 4:2:0 (MPEG1)

  • 4:2:2 to 4:2:0 (MPEG2)

These options specify upsampling operations:

  • 4:2:2 to 4:4:4

  • 4:2:0 (MPEG1) to 4:2:2

  • 4:2:0 (MPEG1) to 4:4:4

  • 4:2:0 (MPEG2) to 4:2:2

  • 4:2:0 (MPEG2) to 4:4:4

  • 4:1:1 to 4:4:4

For more information, see Chrominance Resampling Formats.

Specify the lowpass filter that the block uses to prevent aliasing.

  • Default — The block uses a built-in lowpass filter.

  • User-defined — Specify custom filter coefficients for the block. Depending on the value of the Resampling parameter, this option enables the Horizontal filter coefficients parameter, the Vertical filter coefficients parameter, or both.

  • None — The block does not filter the input signal.

Dependencies

To enable this parameter, set the Resampling parameter to one of these options:

  • 4:4:4 to 4:2:2

  • 4:4:4 to 4:2:0 (MPEG1)

  • 4:4:4 to 4:2:0 (MPEG2)

  • 4:4:4 to 4:1:1

  • 4:2:2 to 4:2:0 (MPEG1)

  • 4:2:2 to 4:2:0 (MPEG2)

.

Specify the horizontal filter coefficients as a vector of even number of elements to apply to your input signal.

Dependencies

To enable this parameter, you must:

  • Set the Resampling parameter to one of these options:

    • 4:4:4 to 4:2:2

    • 4:4:4 to 4:2:0 (MPEG1)

    • 4:4:4 to 4:2:0 (MPEG2)

    • 4:4:4 to 4:1:1

  • Set the Antialiasing filter parameter to User-defined.

Specify the filter coefficients as a vector of odd number of elements to apply to your input signal.

Dependencies

To enable this parameter, you must:

  • Set the Resampling parameter to one of these options:

    • 4:4:4 to 4:2:0 (MPEG1)

    • 4:4:4 to 4:2:0 (MPEG2)

    • 4:2:2 to 4:2:0 (MPEG1)

    • 4:2:2 to 4:2:0 (MPEG2)

  • Set the Antialiasing filter parameter to User-defined.

Specify whether the block uses linear interpolation or pixel replication interpolation to approximate the missing chrominance values when upsampling an image.

  • linear — The block uses linear interpolation to calculate the missing values.

  • pixel replication — The block replicates the chrominance values of the neighboring pixels to assign values to the additional pixels in the upsampled image.

Dependencies

To enable this parameter, set the Resampling parameter to one of these options:

  • 4:2:2 to 4:4:4

  • 4:2:0 (MPEG1) to 4:2:2

  • 4:2:0 (MPEG1) to 4:4:4

  • 4:2:0 (MPEG2) to 4:2:2

  • 4:2:0 (MPEG2) to 4:4:4

  • 4:1:1 to 4:4:4

.

Enable this parameter to read data elements row-wise.

Block Characteristics

Data Types

double | integer | single

Multidimensional Signals

no

Variable-Size Signals

yes

Algorithms

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References

[1] Haskell, Barry G., Atul Puri, and Arun N. Netravali. Digital Video: An Introduction to MPEG-2. Digital Multimedia Standards Series. New York: Chapman & Hall : International Thomson Pub, 1997.

[2] Wang, Yao, Jörn Ostermann, and Ya-Qin Zhang. Video Processing and Communications. Prentice-Hall Signal Processing Series. Upper Saddle River, N.J: Prentice Hall, 2002.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced before R2006a