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author Guido van Rossum <guido@python.org>
date Thu, 17 Jul 1997 16:29:42 +0000
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children 3468ea8645ca
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1 \section{Built-in Module \sectcode{audio}}
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2 \bimodindex{audio}
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3
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4 \strong{Note:} This module is obsolete, since the hardware to which it
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5 interfaces is obsolete. For audio on the Indigo or 4D/35, see
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6 built-in module \code{al} above.
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7
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8 This module provides rudimentary access to the audio I/O device
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9 \file{/dev/audio} on the Silicon Graphics Personal IRIS 4D/25;
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10 see {\it audio}(7). It supports the following operations:
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11
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12 \renewcommand{\indexsubitem}{(in module audio)}
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13 \begin{funcdesc}{setoutgain}{n}
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14 Sets the output gain.
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15 \iftexi
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16 \code{0 <= \var{n} < 256}.
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17 \else
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18 $0 \leq \var{n} < 256$.
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19 %%JHXXX Sets the output gain (0-255).
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20 \fi
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21 \end{funcdesc}
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22
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23 \begin{funcdesc}{getoutgain}{}
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24 Returns the output gain.
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25 \end{funcdesc}
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26
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27 \begin{funcdesc}{setrate}{n}
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28 Sets the sampling rate: \code{1} = 32K/sec, \code{2} = 16K/sec,
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29 \code{3} = 8K/sec.
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30 \end{funcdesc}
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31
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32 \begin{funcdesc}{setduration}{n}
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33 Sets the `sound duration' in units of 1/100 seconds.
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34 \end{funcdesc}
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35
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36 \begin{funcdesc}{read}{n}
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37 Reads a chunk of
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38 \var{n}
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39 sampled bytes from the audio input (line in or microphone).
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40 The chunk is returned as a string of length n.
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41 Each byte encodes one sample as a signed 8-bit quantity using linear
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42 encoding.
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43 This string can be converted to numbers using \code{chr2num()} described
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44 below.
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45 \end{funcdesc}
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46
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47 \begin{funcdesc}{write}{buf}
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48 Writes a chunk of samples to the audio output (speaker).
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49 \end{funcdesc}
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50
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51 These operations support asynchronous audio I/O:
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52
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53 \renewcommand{\indexsubitem}{(in module audio)}
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54 \begin{funcdesc}{start_recording}{n}
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55 Starts a second thread (a process with shared memory) that begins reading
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56 \var{n}
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57 bytes from the audio device.
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58 The main thread immediately continues.
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59 \end{funcdesc}
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60
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61 \begin{funcdesc}{wait_recording}{}
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62 Waits for the second thread to finish and returns the data read.
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63 \end{funcdesc}
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64
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65 \begin{funcdesc}{stop_recording}{}
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66 Makes the second thread stop reading as soon as possible.
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67 Returns the data read so far.
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68 \end{funcdesc}
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69
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70 \begin{funcdesc}{poll_recording}{}
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71 Returns true if the second thread has finished reading (so
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72 \code{wait_recording()} would return the data without delay).
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73 \end{funcdesc}
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74
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75 \begin{funcdesc}{start_playing}{}
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76 \funcline{wait_playing}{}
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77 \funcline{stop_playing}{}
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78 \funcline{poll_playing}{}
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79 \begin{sloppypar}
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80 Similar but for output.
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81 \code{stop_playing()}
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82 returns a lower bound for the number of bytes actually played (not very
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83 accurate).
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84 \end{sloppypar}
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85 \end{funcdesc}
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86
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87 The following operations do not affect the audio device but are
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88 implemented in C for efficiency:
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89
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90 \renewcommand{\indexsubitem}{(in module audio)}
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91 \begin{funcdesc}{amplify}{buf\, f1\, f2}
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92 Amplifies a chunk of samples by a variable factor changing from
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93 \code{\var{f1}/256} to \code{\var{f2}/256.}
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94 Negative factors are allowed.
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95 Resulting values that are to large to fit in a byte are clipped.
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96 \end{funcdesc}
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97
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98 \begin{funcdesc}{reverse}{buf}
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99 Returns a chunk of samples backwards.
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100 \end{funcdesc}
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101
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102 \begin{funcdesc}{add}{buf1\, buf2}
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103 Bytewise adds two chunks of samples.
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104 Bytes that exceed the range are clipped.
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105 If one buffer is shorter, it is assumed to be padded with zeros.
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106 \end{funcdesc}
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107
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108 \begin{funcdesc}{chr2num}{buf}
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109 Converts a string of sampled bytes as returned by \code{read()} into
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110 a list containing the numeric values of the samples.
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111 \end{funcdesc}
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112
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113 \begin{funcdesc}{num2chr}{list}
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114 \begin{sloppypar}
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115 Converts a list as returned by
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116 \code{chr2num()}
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117 back to a buffer acceptable by
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118 \code{write()}.
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119 \end{sloppypar}
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120 \end{funcdesc}