(8.D.2.7) Rebuffer
- Sam Stuart
- Gary Worsham
Overview
Overlaps data into larger block sizes. The underlying time base is preserved.
Discussion
A rebuffer module converts from a smaller to a larger block size, with overlap. The module can support an artibrary number of channels and also supports any 32-bit data type (integer and floating-point). An internal buffer holds the overlap between samples.
At instantiation time, the output block size is specified by the variable OUTBLOCKSIZE. If OUTBLOCKSIZE is positive (e.g., 64), then a specific output block size (64) is set. If OUTBLOCKSIZE is negative (e.g., -4), then this specifies that the output block size is 4 times greater than the input block size.
Even though the output block size is larger, the block output rate is the same as the input block rate. That is, this module does not change the fundamental block time. Assume the bufferBlockSize = -4. The output block size is now 4*block size. In the table below, assume as we move down the table, time increases by one block period for each row. Each row represents one output block. Only one new buffer is added to the output block per block period, but a row of data is output.
Time | Â | Â | Â | Â |
0 | Buffer1 | - | - | - |
1 | Buffer2 | Buffer1 | - | - |
2 | Buffer3 | Buffer2 | Buffer1 | - |
3 | Buffer4 | Buffer3 | Buffer2 | Buffer1 |
4 | Buffer5 | Buffer4 | Buffer3 | Buffer2 |
5 | Buffer6 | Buffer5 | Buffer4 | Buffer3 |
Type Definition
typedef struct _ModuleRebuffer
{
ModuleInstanceDescriptor instance; // Common Audio Weaver module instance structure
INT32 outBlockSize; // Specifies the size of the output block. Positive values indicate a specific block size, in samples. Negative values specify a multiplicative factor between the input and output block sizes.
INT32 overlap; // Number of samples of overlap between blocks. Set by the prebuild function.
INT32 stateIndex; // Index of the oldest state variable in the array of state variables.
FLOAT32* state; // State variable array.
} ModuleRebufferClass;Variables
Properties
Name | Type | Usage | isHidden | Default value | Range | Units |
outBlockSize | int | const | 0 | -2 | -32:100000 | Â |
overlap | int | const | 1 | 32 | Unrestricted | Â |
stateIndex | int | state | 1 | 0 | Unrestricted | Â |
state | float* | state | 1 | [32 x 1] | Unrestricted | Â |
Pins
Input Pins
Name: in
Description: audio input
Data type: {float, int, fract32}
Channel range: Unrestricted
Block size range: Unrestricted
Sample rate range: Unrestricted
Complex support: Real and Complex
Output Pins
Name: out
Description: audio output
Data type: {float, int, fract32}
MATLAB Usage
File Name: rebuffer_module.m
M=rebuffer_module(NAME, OUTBLOCKSIZE)
Creates a rebuffering module which changes the output block size. The
module performs buffering and generates output blocks that overlap in
time. The output blocks are generated at the same rate as the input
blocks.
Arguments:
NAME - name of the module.
OUTBLOCKSIZE - number of samples in each output block.
The amount of overlap equals OUTBLOCKSIZE - M.inputPin{1}.type.blockSize.
That is, the difference between the output and input block sizes.
The module supports an arbitrary number of channels. Each channel is
processed independently.
If OUTBLOCKSIZE is positive, then it is treated as the specific size of
the output block (as in the above discussion). If OUTBLOCKSIZE is
negative, then it is treated as an integer multiplicative factor between
the input and output block sizes. For example, if OUTBLOCKSIZE = -3, then
the output block size equals 3 times the input block size.Â