[nextBufferAddress, underflow, overflow] = Datapixx(‘WriteAudioBuffer’, bufferData [, bufferAddress=16e6]);
Download audio data from local host to a Datapixx internal waveform buffer.
-“bufferData” is a 2D matrix of audio waveform data in the range -1 to +1. The
first row of the matrix contains data for the left ear, and the second row
contains data for the right-ear. A mono dataset will only have a single row.
-“bufferAddress” is the byte address in Datapixx RAM where the buffer should
start. Specifying a bufferAddress of -1 will cause bufferData to be streamed to
the end of the buffer which was last defined in SetAudioSchedule, and
initialized by a call to WriteAudioBuffer with bufferAddress not set to -1.
-“nextBufferAddress” is the next Datapixx address after bufferData has been
downloaded. Multiple contiguous audio waveforms can be downloaded by passing the
returned nextBufferAddress of one waveform as the bufferAddress of the next
waveform. The Datapixx typically has 128 MB of internal RAM which is shared
between all I/O subsystems (DAC/ADC/AUDIO, etc). Datapixx(‘GetRamSize’) can be
used to query the quantity of RAM in your system.
-“underflow” or “overflow” are set to 1 if streaming calls to WriteAudioBuffer
supply insufficient, or too much, data. If bufferAddress is passed a value of
-1, then WriteAudioBuffer is streaming continuous waveform data into a circular
buffer. Streaming playback must ensure that the provided data always remains
ahead of the playback position, without providing more data than can fit in the
playback buffer. The freeBufferFrames field returned by GetAudioStatus indicates
the maximum number of columns which can be written by WriteAudioBuffer. If more
than this number of frames is written, an overflow occurs and there will be a
glitch in the generated waveform. If the streaming data is not supplied quickly
enough, then old data will be played, also causing a glitch. In addition to
returning underflow/overflow flags, these errors will increment the
numStreamUnderflows/numStreamOverflows fields returned by GetAudioStatus.
See DatapixxSimonGame, DatapixxAudio*Demo files for examples.