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<H2><A NAME="SECTION00161110000000000000000"></A><A NAME="ossaudio-device-objects"></A>
<BR>
14.11.1 Audio Device Objects 
</H2>

<P>
Before you can write to or read from an audio device, you must call
three methods in the correct order:

<OL>
<LI><tt class="method">setfmt()</tt> to set the output format
</LI>
<LI><tt class="method">channels()</tt> to set the number of channels
</LI>
<LI><tt class="method">speed()</tt> to set the sample rate
</LI>
</OL>
Alternately, you can use the <tt class="method">setparameters()</tt> method to set all
three audio parameters at once.  This is more convenient, but may not be
as flexible in all cases.

<P>
The audio device objects returned by <tt class="function">open()</tt> define the
following methods:

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-4775' xml:id='l2h-4775' class="method">close</tt></b>(</nobr></td>
  <td><var></var>)</td></tr></table></dt>
<dd>
Explicitly close the audio device.  When you are done writing to or
reading from an audio device, you should explicitly close it.  A closed
device cannot be used again.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-4776' xml:id='l2h-4776' class="method">fileno</tt></b>(</nobr></td>
  <td><var></var>)</td></tr></table></dt>
<dd>
Return the file descriptor associated with the device.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-4777' xml:id='l2h-4777' class="method">read</tt></b>(</nobr></td>
  <td><var>size</var>)</td></tr></table></dt>
<dd>
Read <var>size</var> bytes from the audio input and return them as a Python
string.  Unlike most <span class="Unix">Unix</span> device drivers, OSS audio devices in
blocking mode (the default) will block <tt class="function">read()</tt> until the
entire requested amount of data is available.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-4778' xml:id='l2h-4778' class="method">write</tt></b>(</nobr></td>
  <td><var>data</var>)</td></tr></table></dt>
<dd>
Write the Python string <var>data</var> to the audio device and return the
number of bytes written.  If the audio device is in blocking mode (the
default), the entire string is always written (again, this is different
from usual <span class="Unix">Unix</span> device semantics).  If the device is in non-blocking
mode, some data may not be written--see <tt class="method">writeall()</tt>.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-4779' xml:id='l2h-4779' class="method">writeall</tt></b>(</nobr></td>
  <td><var>data</var>)</td></tr></table></dt>
<dd>
Write the entire Python string <var>data</var> to the audio device: waits
until the audio device is able to accept data, writes as much data as it
will accept, and repeats until <var>data</var> has been completely written.
If the device is in blocking mode (the default), this has the same
effect as <tt class="method">write()</tt>; <tt class="method">writeall()</tt> is only useful in
non-blocking mode.  Has no return value, since the amount of data
written is always equal to the amount of data supplied.
</dl>

<P>
The following methods each map to exactly one
<tt class="function">ioctl()</tt> system call.  The correspondence is obvious: for
example, <tt class="method">setfmt()</tt> corresponds to the <code>SNDCTL_DSP_SETFMT</code>
ioctl, and <tt class="method">sync()</tt> to <code>SNDCTL_DSP_SYNC</code> (this can be useful
when consulting the OSS documentation).  If the underlying
<tt class="function">ioctl()</tt> fails, they all raise <tt class="exception">IOError</tt>.

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-4780' xml:id='l2h-4780' class="method">nonblock</tt></b>(</nobr></td>
  <td><var></var>)</td></tr></table></dt>
<dd>
Put the device into non-blocking mode.  Once in non-blocking mode, there
is no way to return it to blocking mode.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-4781' xml:id='l2h-4781' class="method">getfmts</tt></b>(</nobr></td>
  <td><var></var>)</td></tr></table></dt>
<dd>
Return a bitmask of the audio output formats supported by the
soundcard.  Some of the formats supported by OSS are:

<P>
<div class="center"><table class="realtable">
  <thead>
    <tr>
      <th class="left"  >Format</th>
      <th class="left"  >Description</th>
      </tr>
    </thead>
  <tbody>
    <tr><td class="left"   valign="baseline">AFMT_MU_LAW</td>
        <td class="left"  >a logarithmic encoding (used by Sun <code>.au</code> files and
        <span class="file">/dev/audio</span>)</td></tr>
    <tr><td class="left"   valign="baseline">AFMT_A_LAW</td>
        <td class="left"  >a logarithmic encoding</td></tr>
    <tr><td class="left"   valign="baseline">AFMT_IMA_ADPCM</td>
        <td class="left"  >a 4:1 compressed format defined by the Interactive Multimedia
        Association</td></tr>
    <tr><td class="left"   valign="baseline">AFMT_U8</td>
        <td class="left"  >Unsigned, 8-bit audio</td></tr>
    <tr><td class="left"   valign="baseline">AFMT_S16_LE</td>
        <td class="left"  >Signed, 16-bit audio, little-endian byte order (as used by
        Intel processors)</td></tr>
    <tr><td class="left"   valign="baseline">AFMT_S16_BE</td>
        <td class="left"  >Signed, 16-bit audio, big-endian byte order (as used by 68k,
        PowerPC, Sparc)</td></tr>
    <tr><td class="left"   valign="baseline">AFMT_S8</td>
        <td class="left"  >Signed, 8 bit audio</td></tr>
    <tr><td class="left"   valign="baseline">AFMT_U16_LE</td>
        <td class="left"  >Unsigned, 16-bit little-endian audio</td></tr>
    <tr><td class="left"   valign="baseline">AFMT_U16_BE</td>
        <td class="left"  >Unsigned, 16-bit big-endian audio</td></tr></tbody>
</table></div>
Consult the OSS documentation for a full list of audio formats, and note
that most devices support only a subset of these formats.  Some older
devices only support <tt class="constant">AFMT_U8</tt>; the most common format used
today is <tt class="constant">AFMT_S16_LE</tt>.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-4782' xml:id='l2h-4782' class="method">setfmt</tt></b>(</nobr></td>
  <td><var>format</var>)</td></tr></table></dt>
<dd>
Try to set the current audio format to <var>format</var>--see
<tt class="method">getfmts()</tt> for a list.  Returns the audio format that the device
was set to, which may not be the requested format.  May also be used to
return the current audio format--do this by passing an ``audio format''
of
<tt class="constant">AFMT_QUERY</tt>.  
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-4783' xml:id='l2h-4783' class="method">channels</tt></b>(</nobr></td>
  <td><var>nchannels</var>)</td></tr></table></dt>
<dd>
Set the number of output channels to <var>nchannels</var>.  A value of 1
indicates monophonic sound, 2 stereophonic.  Some devices may have more
than 2 channels, and some high-end devices may not support mono.
Returns the number of channels the device was set to.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-4784' xml:id='l2h-4784' class="method">speed</tt></b>(</nobr></td>
  <td><var>samplerate</var>)</td></tr></table></dt>
<dd>
Try to set the audio sampling rate to <var>samplerate</var> samples per
second.  Returns the rate actually set.  Most sound devices don't
support arbitrary sampling rates.  Common rates are:
<div class="center"><table class="realtable">
  <thead>
    <tr>
      <th class="left"  >Rate</th>
      <th class="left"  >Description</th>
      </tr>
    </thead>
  <tbody>
    <tr><td class="left"   valign="baseline">8000</td>
        <td class="left"  >default rate for <span class="file">/dev/audio</span></td></tr>
    <tr><td class="left"   valign="baseline">11025</td>
        <td class="left"  >speech recording</td></tr>
    <tr><td class="left"   valign="baseline">22050</td>
        <td class="left"  ></td></tr>
    <tr><td class="left"   valign="baseline">44100</td>
        <td class="left"  >CD quality audio (at 16 bits/sample and 2 channels)</td></tr>
    <tr><td class="left"   valign="baseline">96000</td>
        <td class="left"  >DVD quality audio (at 24 bits/sample)</td></tr></tbody>
</table></div>
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-4785' xml:id='l2h-4785' class="method">sync</tt></b>(</nobr></td>
  <td><var></var>)</td></tr></table></dt>
<dd>
Wait until the sound device has played every byte in its buffer.  (This
happens implicitly when the device is closed.)  The OSS documentation
recommends closing and re-opening the device rather than using
<tt class="method">sync()</tt>.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-4786' xml:id='l2h-4786' class="method">reset</tt></b>(</nobr></td>
  <td><var></var>)</td></tr></table></dt>
<dd>
Immediately stop playing or recording and return the device to a
state where it can accept commands.  The OSS documentation recommends
closing and re-opening the device after calling <tt class="method">reset()</tt>.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-4787' xml:id='l2h-4787' class="method">post</tt></b>(</nobr></td>
  <td><var></var>)</td></tr></table></dt>
<dd>
Tell the driver that there is likely to be a pause in the output, making
it possible for the device to handle the pause more intelligently.  You
might use this after playing a spot sound effect, before waiting for
user input, or before doing disk I/O.
</dl>

<P>
The following convenience methods combine several ioctls, or one ioctl
and some simple calculations.

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-4788' xml:id='l2h-4788' class="method">setparameters</tt></b>(</nobr></td>
  <td><var>format, nchannels, samplerate </var><big>[</big><var>, strict=False</var><big>]</big><var></var>)</td></tr></table></dt>
<dd>

<P>
Set the key audio sampling parameters--sample format, number of
channels, and sampling rate--in one method call.  <var>format</var>, 
<var>nchannels</var>, and <var>samplerate</var> should be as specified in the
<tt class="method">setfmt()</tt>, <tt class="method">channels()</tt>, and <tt class="method">speed()</tt> 
methods.  If <var>strict</var> is true, <tt class="method">setparameters()</tt> checks to
see if each parameter was actually set to the requested value, and
raises <tt class="exception">OSSAudioError</tt> if not.  Returns a tuple (<var>format</var>,
<var>nchannels</var>, <var>samplerate</var>) indicating the parameter values that
were actually set by the device driver (i.e., the same as the return
values of <tt class="method">setfmt()</tt>, <tt class="method">channels()</tt>, and <tt class="method">speed()</tt>).

<P>
For example,
<div class="verbatim"><pre>
  (fmt, channels, rate) = dsp.setparameters(fmt, channels, rate)
</pre></div>
is equivalent to
<div class="verbatim"><pre>
  fmt = dsp.setfmt(fmt)
  channels = dsp.channels(channels)
  rate = dsp.rate(channels)
</pre></div>
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-4789' xml:id='l2h-4789' class="method">bufsize</tt></b>(</nobr></td>
  <td><var></var>)</td></tr></table></dt>
<dd>
Returns the size of the hardware buffer, in samples.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-4790' xml:id='l2h-4790' class="method">obufcount</tt></b>(</nobr></td>
  <td><var></var>)</td></tr></table></dt>
<dd>
Returns the number of samples that are in the hardware buffer yet to be
played.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-4791' xml:id='l2h-4791' class="method">obuffree</tt></b>(</nobr></td>
  <td><var></var>)</td></tr></table></dt>
<dd>
Returns the number of samples that could be queued into the hardware
buffer to be played without blocking.
</dl>

<P>

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	55	<H2><A NAME="SECTION00161110000000000000000"></A><A NAME="ossaudio-device-objects"></A>
	56	<BR>
	57	14.11.1 Audio Device Objects
	58	</H2>
	59
	60	<P>
	61	Before you can write to or read from an audio device, you must call
	62	three methods in the correct order:
	63
	64	<OL>
65	<LI><tt class="method">setfmt()</tt> to set the output format
66	</LI>
67	<LI><tt class="method">channels()</tt> to set the number of channels
68	</LI>
69	<LI><tt class="method">speed()</tt> to set the sample rate
70	</LI>
71	</OL>
72	Alternately, you can use the <tt class="method">setparameters()</tt> method to set all
73	three audio parameters at once. This is more convenient, but may not be
74	as flexible in all cases.
75
76	<P>
77	The audio device objects returned by <tt class="function">open()</tt> define the
78	following methods:
79
80	<P>
81	<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
82	<td><nobr><b><tt id='l2h-4775' xml:id='l2h-4775' class="method">close</tt></b>(</nobr></td>
83	<td><var></var>)</td></tr></table></dt>
84	<dd>
85	Explicitly close the audio device. When you are done writing to or
86	reading from an audio device, you should explicitly close it. A closed
87	device cannot be used again.
88	</dl>
89
90	<P>
91	<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
92	<td><nobr><b><tt id='l2h-4776' xml:id='l2h-4776' class="method">fileno</tt></b>(</nobr></td>
93	<td><var></var>)</td></tr></table></dt>
94	<dd>
95	Return the file descriptor associated with the device.
96	</dl>
97
98	<P>
99	<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
100	<td><nobr><b><tt id='l2h-4777' xml:id='l2h-4777' class="method">read</tt></b>(</nobr></td>
101	<td><var>size</var>)</td></tr></table></dt>
102	<dd>
103	Read <var>size</var> bytes from the audio input and return them as a Python
104	string. Unlike most <span class="Unix">Unix</span> device drivers, OSS audio devices in
105	blocking mode (the default) will block <tt class="function">read()</tt> until the
106	entire requested amount of data is available.
107	</dl>
108
109	<P>
110	<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
111	<td><nobr><b><tt id='l2h-4778' xml:id='l2h-4778' class="method">write</tt></b>(</nobr></td>
112	<td><var>data</var>)</td></tr></table></dt>
113	<dd>
114	Write the Python string <var>data</var> to the audio device and return the
115	number of bytes written. If the audio device is in blocking mode (the
116	default), the entire string is always written (again, this is different
117	from usual <span class="Unix">Unix</span> device semantics). If the device is in non-blocking
118	mode, some data may not be written--see <tt class="method">writeall()</tt>.
119	</dl>
120
121	<P>
122	<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
123	<td><nobr><b><tt id='l2h-4779' xml:id='l2h-4779' class="method">writeall</tt></b>(</nobr></td>
124	<td><var>data</var>)</td></tr></table></dt>
125	<dd>
126	Write the entire Python string <var>data</var> to the audio device: waits
127	until the audio device is able to accept data, writes as much data as it
128	will accept, and repeats until <var>data</var> has been completely written.
129	If the device is in blocking mode (the default), this has the same
130	effect as <tt class="method">write()</tt>; <tt class="method">writeall()</tt> is only useful in
131	non-blocking mode. Has no return value, since the amount of data
132	written is always equal to the amount of data supplied.
133	</dl>
134
135	<P>
136	The following methods each map to exactly one
137	<tt class="function">ioctl()</tt> system call. The correspondence is obvious: for
138	example, <tt class="method">setfmt()</tt> corresponds to the <code>SNDCTL_DSP_SETFMT</code>
139	ioctl, and <tt class="method">sync()</tt> to <code>SNDCTL_DSP_SYNC</code> (this can be useful
140	when consulting the OSS documentation). If the underlying
141	<tt class="function">ioctl()</tt> fails, they all raise <tt class="exception">IOError</tt>.
142
143	<P>
144	<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
145	<td><nobr><b><tt id='l2h-4780' xml:id='l2h-4780' class="method">nonblock</tt></b>(</nobr></td>
146	<td><var></var>)</td></tr></table></dt>
147	<dd>
148	Put the device into non-blocking mode. Once in non-blocking mode, there
149	is no way to return it to blocking mode.
150	</dl>
151
152	<P>
153	<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
154	<td><nobr><b><tt id='l2h-4781' xml:id='l2h-4781' class="method">getfmts</tt></b>(</nobr></td>
155	<td><var></var>)</td></tr></table></dt>
156	<dd>
157	Return a bitmask of the audio output formats supported by the
158	soundcard. Some of the formats supported by OSS are:
159
160	<P>
161	<div class="center"><table class="realtable">
162	<thead>
163	<tr>
164	<th class="left" >Format</th>
165	<th class="left" >Description</th>
166	</tr>
167	</thead>
168	<tbody>
169	<tr><td class="left" valign="baseline">AFMT_MU_LAW</td>
170	<td class="left" >a logarithmic encoding (used by Sun <code>.au</code> files and
171	<span class="file">/dev/audio</span>)</td></tr>
172	<tr><td class="left" valign="baseline">AFMT_A_LAW</td>
173	<td class="left" >a logarithmic encoding</td></tr>
174	<tr><td class="left" valign="baseline">AFMT_IMA_ADPCM</td>
175	<td class="left" >a 4:1 compressed format defined by the Interactive Multimedia
176	Association</td></tr>
177	<tr><td class="left" valign="baseline">AFMT_U8</td>
178	<td class="left" >Unsigned, 8-bit audio</td></tr>
179	<tr><td class="left" valign="baseline">AFMT_S16_LE</td>
180	<td class="left" >Signed, 16-bit audio, little-endian byte order (as used by
181	Intel processors)</td></tr>
182	<tr><td class="left" valign="baseline">AFMT_S16_BE</td>
183	<td class="left" >Signed, 16-bit audio, big-endian byte order (as used by 68k,
184	PowerPC, Sparc)</td></tr>
185	<tr><td class="left" valign="baseline">AFMT_S8</td>
186	<td class="left" >Signed, 8 bit audio</td></tr>
187	<tr><td class="left" valign="baseline">AFMT_U16_LE</td>
188	<td class="left" >Unsigned, 16-bit little-endian audio</td></tr>
189	<tr><td class="left" valign="baseline">AFMT_U16_BE</td>
190	<td class="left" >Unsigned, 16-bit big-endian audio</td></tr></tbody>
191	</table></div>
192	Consult the OSS documentation for a full list of audio formats, and note
193	that most devices support only a subset of these formats. Some older
194	devices only support <tt class="constant">AFMT_U8</tt>; the most common format used
195	today is <tt class="constant">AFMT_S16_LE</tt>.
196	</dl>
197
198	<P>
199	<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
200	<td><nobr><b><tt id='l2h-4782' xml:id='l2h-4782' class="method">setfmt</tt></b>(</nobr></td>
201	<td><var>format</var>)</td></tr></table></dt>
202	<dd>
203	Try to set the current audio format to <var>format</var>--see
204	<tt class="method">getfmts()</tt> for a list. Returns the audio format that the device
205	was set to, which may not be the requested format. May also be used to
206	return the current audio format--do this by passing an ``audio format''
207	of
208	<tt class="constant">AFMT_QUERY</tt>.
209	</dl>
210
211	<P>
212	<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
213	<td><nobr><b><tt id='l2h-4783' xml:id='l2h-4783' class="method">channels</tt></b>(</nobr></td>
214	<td><var>nchannels</var>)</td></tr></table></dt>
215	<dd>
216	Set the number of output channels to <var>nchannels</var>. A value of 1
217	indicates monophonic sound, 2 stereophonic. Some devices may have more
218	than 2 channels, and some high-end devices may not support mono.
219	Returns the number of channels the device was set to.
220	</dl>
221
222	<P>
223	<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
224	<td><nobr><b><tt id='l2h-4784' xml:id='l2h-4784' class="method">speed</tt></b>(</nobr></td>
225	<td><var>samplerate</var>)</td></tr></table></dt>
226	<dd>
227	Try to set the audio sampling rate to <var>samplerate</var> samples per
228	second. Returns the rate actually set. Most sound devices don't
229	support arbitrary sampling rates. Common rates are:
230	<div class="center"><table class="realtable">
231	<thead>
232	<tr>
233	<th class="left" >Rate</th>
234	<th class="left" >Description</th>
235	</tr>
236	</thead>
237	<tbody>
238	<tr><td class="left" valign="baseline">8000</td>
239	<td class="left" >default rate for <span class="file">/dev/audio</span></td></tr>
240	<tr><td class="left" valign="baseline">11025</td>
241	<td class="left" >speech recording</td></tr>
242	<tr><td class="left" valign="baseline">22050</td>
243	<td class="left" ></td></tr>
244	<tr><td class="left" valign="baseline">44100</td>
245	<td class="left" >CD quality audio (at 16 bits/sample and 2 channels)</td></tr>
246	<tr><td class="left" valign="baseline">96000</td>
247	<td class="left" >DVD quality audio (at 24 bits/sample)</td></tr></tbody>
248	</table></div>
249	</dl>
250
251	<P>
252	<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
253	<td><nobr><b><tt id='l2h-4785' xml:id='l2h-4785' class="method">sync</tt></b>(</nobr></td>
254	<td><var></var>)</td></tr></table></dt>
255	<dd>
256	Wait until the sound device has played every byte in its buffer. (This
257	happens implicitly when the device is closed.) The OSS documentation
258	recommends closing and re-opening the device rather than using
259	<tt class="method">sync()</tt>.
260	</dl>
261
262	<P>
263	<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
264	<td><nobr><b><tt id='l2h-4786' xml:id='l2h-4786' class="method">reset</tt></b>(</nobr></td>
265	<td><var></var>)</td></tr></table></dt>
266	<dd>
267	Immediately stop playing or recording and return the device to a
268	state where it can accept commands. The OSS documentation recommends
269	closing and re-opening the device after calling <tt class="method">reset()</tt>.
270	</dl>
271
272	<P>
273	<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
274	<td><nobr><b><tt id='l2h-4787' xml:id='l2h-4787' class="method">post</tt></b>(</nobr></td>
275	<td><var></var>)</td></tr></table></dt>
276	<dd>
277	Tell the driver that there is likely to be a pause in the output, making
278	it possible for the device to handle the pause more intelligently. You
279	might use this after playing a spot sound effect, before waiting for
280	user input, or before doing disk I/O.
281	</dl>
282
283	<P>
284	The following convenience methods combine several ioctls, or one ioctl
285	and some simple calculations.
286
287	<P>
288	<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
289	<td><nobr><b><tt id='l2h-4788' xml:id='l2h-4788' class="method">setparameters</tt></b>(</nobr></td>
290	<td><var>format, nchannels, samplerate </var><big>[</big><var>, strict=False</var><big>]</big><var></var>)</td></tr></table></dt>
291	<dd>
292
293	<P>
294	Set the key audio sampling parameters--sample format, number of
295	channels, and sampling rate--in one method call. <var>format</var>,
296	<var>nchannels</var>, and <var>samplerate</var> should be as specified in the
297	<tt class="method">setfmt()</tt>, <tt class="method">channels()</tt>, and <tt class="method">speed()</tt>
298	methods. If <var>strict</var> is true, <tt class="method">setparameters()</tt> checks to
299	see if each parameter was actually set to the requested value, and
300	raises <tt class="exception">OSSAudioError</tt> if not. Returns a tuple (<var>format</var>,
301	<var>nchannels</var>, <var>samplerate</var>) indicating the parameter values that
302	were actually set by the device driver (i.e., the same as the return
303	values of <tt class="method">setfmt()</tt>, <tt class="method">channels()</tt>, and <tt class="method">speed()</tt>).
304
305	<P>
306	For example,
307	<div class="verbatim"><pre>
308	(fmt, channels, rate) = dsp.setparameters(fmt, channels, rate)
309	</pre></div>
310	is equivalent to
311	<div class="verbatim"><pre>
312	fmt = dsp.setfmt(fmt)
313	channels = dsp.channels(channels)
314	rate = dsp.rate(channels)
315	</pre></div>
316	</dl>
317
318	<P>
319	<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
320	<td><nobr><b><tt id='l2h-4789' xml:id='l2h-4789' class="method">bufsize</tt></b>(</nobr></td>
321	<td><var></var>)</td></tr></table></dt>
322	<dd>
323	Returns the size of the hardware buffer, in samples.
324	</dl>
325
326	<P>
327	<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
328	<td><nobr><b><tt id='l2h-4790' xml:id='l2h-4790' class="method">obufcount</tt></b>(</nobr></td>
329	<td><var></var>)</td></tr></table></dt>
330	<dd>
331	Returns the number of samples that are in the hardware buffer yet to be
332	played.
333	</dl>
334
335	<P>
336	<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
337	<td><nobr><b><tt id='l2h-4791' xml:id='l2h-4791' class="method">obuffree</tt></b>(</nobr></td>
338	<td><var></var>)</td></tr></table></dt>
339	<dd>
340	Returns the number of samples that could be queued into the hardware
341	buffer to be played without blocking.
342	</dl>
343
344	<P>
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