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Pad

Pad or truncate specified dimension(s)

  • Library:
  • DSP System Toolbox / Signal Operations

  • Pad block

Description

The Pad block extends or crops the dimensions of an input signal by padding or truncating along its columns, rows, columns and rows, or along any other dimension(s) that you specify. The block truncates the input when you specify output dimensions that are shorter than the corresponding input dimensions. If the input and output lengths are the same, the block acts as a pass-through.

You can enter the pad value in the block mask or via an input port. You can enter output sizes in the block mask, or have the block pad the specified dimensions until their length is the next highest power of two. The Pad signal at parameter controls whether the block pads or truncates the input signal dimensions at the beginning, end, or both. For odd pad or truncation lengths, the extra pad or truncation value is applied at the end of the signal. When the block is in the Specified dimensions mode, you can specify either the output size or the pad size.

You can configure the block to warn or error when an input signal is truncated using the Action when truncation occurs parameter.

Ports

Input

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Specify the input as a scalar, vector, matrix, or an N-D array.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | Boolean | fixed point
Complex Number Support: Yes

Output

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Output of the Pad block. The size and dimension of the output depends on whether the block has padded or truncated the input along the specified dimension. The data type and complexity of the output matches that of the input.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | Boolean | fixed point
Complex Number Support: Yes

Parameters

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Specify the dimensions over which to pad or truncate:

  • Columns

  • Rows

  • Columns and rows

  • None

  • Specified dimensions

Specify the one-based dimension(s) over which to pad or truncate. The value for this parameter can be a scalar or a vector. For example, specify 1 to pad columns. Specify [1 2] to pad columns and rows. Specify [1 3 5] to pad the first, third, and fifth dimensions.

Dependencies

This parameter appears only when you set Pad over to Specified dimensions.

Choose how you specify the pad value. The pad value can come from the dialog or from an input port:

  • If you select Specify via dialog, the Pad value parameter appears.

  • If you select Input port, the PVal port appears on the block icon.

Specify the constant scalar value with which to pad the input.

Tunable: Yes

Dependencies

This parameter appears only when you set Pad value source to Specify via dialog.

Choose how you specify the column length of the output:

  • If you select User-specified, the Column size parameter appears.

  • If you select Next power of two, the block pads the output columns until their length is the next highest power of two. If the column length is already a power of two, the block does not pad the columns.

Dependencies

This parameter appears only when you set Pad over to Columns or Columns and rows.

Specify the column length of the output. If the specified column length is longer than the input column length, the block pads the columns. If the specified column length is shorter than the input column length, the block truncates the columns.

Dependencies

This parameter appears only when you set Output column mode to User-specified.

Choose how you specify the row length of the output:

  • If you select User-specified, the Row size parameter appears.

  • If you select Next power of two, the block pads the output rows until their length is the next highest power of two. If the row length is already a power of two, the block does not pad the rows.

Dependencies

This parameter appears only when you set Pad over to Rows or Columns and rows.

Specify the row length of the output. If the specified row length is longer than the input row length, the block pads the rows. If the specified row length is shorter than the input row length, the block truncates the rows.

Dependencies

This parameter appears only when you set Output row mode to User-specified.

Choose whether you want to control the output length of the specified dimensions by specifying the output size or the pad size.

Dependencies

This parameter appears only when you set Pad over to Specified dimensions.

Choose how you specify the output length of the specified dimensions:

  • If you select User-specified, the Output size parameter appears.

  • If you select Next power of two, the block pads the specified dimensions until their length is the next highest power of two. If the dimension length is already a power of two, the block does not pad in that dimension.

Dependencies

This parameter appears only when you set Pad over to Specified dimensions and the Specify parameter to Output size.

Specify the output length of the specified dimension(s). This parameter must be a scalar or a vector with the same number of elements as the Dimensions to pad parameter. Each element in the Output size vector gives the output length for the corresponding dimension in the Dimensions to pad vector. If the specified length is longer than the input length for a given dimension, the block pads that dimension. If the specified length is shorter than the input length for a given dimension, the block truncates that dimension.

Dependencies

This parameter appears only when you set Pad over to Specified dimensions and the Specify parameter to Output size.

Specify how many values to add to the beginning of the input signal along the specified dimension(s). This parameter must be a scalar or a vector with the same number of elements as the Dimensions to pad parameter. Each element in the Pad size at beginning parameter gives the pad length at the beginning of the corresponding dimension in the Dimensions to pad parameter. Values of this parameter must be nonnegative integers.

Dependencies

This parameter appears only when you set Pad over to Specified dimensions and the Specify parameter to Pad size.

Specify how many values to add to the end of the input signal along the specified dimension(s). This parameter must be a scalar or a vector with the same number of elements as the Dimensions to pad parameter. Each element in the Pad size at end parameter gives the pad length at the end of the corresponding dimension in the Dimensions to pad parameter. Values of this parameter must be nonnegative integers.

Dependencies

This parameter appears only when you set Pad over to Specified dimensions and the Specify parameter to Pad size.

Specify whether to pad or truncate the signal at the Beginning, End, or Beginning and end of the specified dimension(s). When you select Beginning and end, half the pad length is added to the beginning of the signal and the other half is added to the end of the signal. For an odd pad length, the extra value is added to the end of the signal. When you specify to truncate the signal in this mode, an equal number of values are truncated from the beginning and the end of the signal. In the case of an odd truncation length, the extra value is removed from the end of the signal.

Dependencies

This parameter appears only when you set Pad over to Columns, Rows, and Columns and rows.

Specify the action the block takes when it truncates the input.

  • None –– The block does not notify when the input is truncated.

  • Warning –– The block displays a warning when the input is truncated.

  • Error –– The block displays an error message and terminates the simulation when the input is truncated.

Dependencies

This parameter appears only when you set Pad over to Columns, Rows, and Columns and rows.

Block Characteristics

Data Types

Boolean | double | fixed point | integer | single

Direct Feedthrough

no

Multidimensional Signals

no

Variable-Size Signals

no

Zero-Crossing Detection

no

Extended Capabilities

Fixed-Point Conversion
Design and simulate fixed-point systems using Fixed-Point Designer™.

See Also

Blocks

Introduced before R2006a