Read data from buffer
Read Variable Frame Sizes from Buffer
dsp.AsyncBuffer System object™ supports reading variable frame sizes from the buffer.
dsp.AsyncBuffer System object. The input is white Gaussian noise with a mean of 0, a standard deviation of 1, and a frame size of 512 samples. Write the input to the buffer using the
asyncBuff = dsp.AsyncBuffer; input = randn(512,1); write(asyncBuff,input); plot(input) hold on
Store the data that is read from the buffer in
Plot the input signal and data that is read from the buffer in the same plot. Read data from the buffer until all samples are read. In each iteration of the loop,
randi determines the number of samples to read. Therefore, the signal is read in as a variable-size signal. The
prevIndex variable keeps track of the previous index value that contains the data.
outTotal = zeros(size(input)); prevIndex = 0; while asyncBuff.NumUnreadSamples ~= 0 numToRead = randi([1,64]); out = read(asyncBuff,numToRead); outTotal(prevIndex+1:prevIndex+numToRead) = out; prevIndex = prevIndex+numToRead; end plot(outTotal,'r') hold off
Verify that the input data and the data read from the buffer (excluding the underrun samples, if any) are the same. The cumulative number of overrun and underrun samples in the buffer is determined by the
S = info(asyncBuff)
S = struct with fields: CumulativeOverrun: 0 CumulativeUnderrun: 28
CumulativeUnderrun field shows the number of samples underrun per channel. Underrun occurs if you attempt to read more samples than available.
asyncBuff — Async buffer
Async buffer, specified as a
NumRows — Number of samples read from each channel
Number of samples read from each channel (column) of the buffer, specified as a positive integer. If the requested number of samples is greater than the number of unread samples, the output is zero-padded.
Overlap — Number of samples overlapped
The function returns
NumRows samples from each channel and
overlaps previously read samples by
Overlap. The total number of
samples read is
NumRows × NumChann, where
NumChann is the number of channels in the buffer. The total number
of new samples read is (
× NumChann. If the overlap portion contains samples that are
overwritten, and are therefore not contiguously written, the output is
out — Data read from buffer
vector | matrix
Data read from the buffer, returned as an array of
× NumChann samples. If
specified, the function returns (
Overlap) × NumChann samples. If the
requested number of samples is greater than the number of unread samples, the output is
Complex Number Support: Yes
nUnderrun — Number of samples zero-padded in each channel
vector | matrix
Number of samples zero-padded in each channel (column) if underrun occurred. Underrun occurs if you attempt to read more samples than available. Samples that are zero-padded in overlapped portions are not counted as underrun.
Introduced in R2017a