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* \bcode, \ecode added everywhere
* \label{module-foo} added everywhere
* A few \seealso sections added.
* Indentation fixed inside verbatim in lib*tex files
122 lines
3.4 KiB
TeX
122 lines
3.4 KiB
TeX
\section{Built-in Module \sectcode{audio}}
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\label{module-audio}
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\bimodindex{audio}
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\strong{Note:} This module is obsolete, since the hardware to which it
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interfaces is obsolete. For audio on the Indigo or 4D/35, see
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built-in module \code{al} above.
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This module provides rudimentary access to the audio I/O device
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\file{/dev/audio} on the Silicon Graphics Personal IRIS 4D/25;
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see {\it audio}(7). It supports the following operations:
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\renewcommand{\indexsubitem}{(in module audio)}
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\begin{funcdesc}{setoutgain}{n}
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Sets the output gain.
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\iftexi
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\code{0 <= \var{n} < 256}.
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\else
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$0 \leq \var{n} < 256$.
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%%JHXXX Sets the output gain (0-255).
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\fi
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\end{funcdesc}
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\begin{funcdesc}{getoutgain}{}
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Returns the output gain.
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\end{funcdesc}
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\begin{funcdesc}{setrate}{n}
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Sets the sampling rate: \code{1} = 32K/sec, \code{2} = 16K/sec,
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\code{3} = 8K/sec.
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\end{funcdesc}
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\begin{funcdesc}{setduration}{n}
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Sets the `sound duration' in units of 1/100 seconds.
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\end{funcdesc}
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\begin{funcdesc}{read}{n}
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Reads a chunk of
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\var{n}
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sampled bytes from the audio input (line in or microphone).
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The chunk is returned as a string of length n.
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Each byte encodes one sample as a signed 8-bit quantity using linear
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encoding.
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This string can be converted to numbers using \code{chr2num()} described
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below.
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\end{funcdesc}
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\begin{funcdesc}{write}{buf}
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Writes a chunk of samples to the audio output (speaker).
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\end{funcdesc}
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These operations support asynchronous audio I/O:
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\renewcommand{\indexsubitem}{(in module audio)}
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\begin{funcdesc}{start_recording}{n}
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Starts a second thread (a process with shared memory) that begins reading
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\var{n}
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bytes from the audio device.
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The main thread immediately continues.
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\end{funcdesc}
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\begin{funcdesc}{wait_recording}{}
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Waits for the second thread to finish and returns the data read.
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\end{funcdesc}
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\begin{funcdesc}{stop_recording}{}
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Makes the second thread stop reading as soon as possible.
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Returns the data read so far.
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\end{funcdesc}
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\begin{funcdesc}{poll_recording}{}
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Returns true if the second thread has finished reading (so
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\code{wait_recording()} would return the data without delay).
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\end{funcdesc}
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\begin{funcdesc}{start_playing}{}
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\funcline{wait_playing}{}
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\funcline{stop_playing}{}
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\funcline{poll_playing}{}
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\begin{sloppypar}
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Similar but for output.
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\code{stop_playing()}
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returns a lower bound for the number of bytes actually played (not very
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accurate).
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\end{sloppypar}
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\end{funcdesc}
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The following operations do not affect the audio device but are
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implemented in C for efficiency:
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\renewcommand{\indexsubitem}{(in module audio)}
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\begin{funcdesc}{amplify}{buf\, f1\, f2}
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Amplifies a chunk of samples by a variable factor changing from
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\code{\var{f1}/256} to \code{\var{f2}/256.}
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Negative factors are allowed.
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Resulting values that are to large to fit in a byte are clipped.
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\end{funcdesc}
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\begin{funcdesc}{reverse}{buf}
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Returns a chunk of samples backwards.
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\end{funcdesc}
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\begin{funcdesc}{add}{buf1\, buf2}
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Bytewise adds two chunks of samples.
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Bytes that exceed the range are clipped.
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If one buffer is shorter, it is assumed to be padded with zeros.
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\end{funcdesc}
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\begin{funcdesc}{chr2num}{buf}
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Converts a string of sampled bytes as returned by \code{read()} into
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a list containing the numeric values of the samples.
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\end{funcdesc}
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\begin{funcdesc}{num2chr}{list}
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\begin{sloppypar}
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Converts a list as returned by
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\code{chr2num()}
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back to a buffer acceptable by
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\code{write()}.
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\end{sloppypar}
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\end{funcdesc}
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