1page.title=Audio Attributes
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19<div id="qv-wrapper">
20  <div id="qv">
21    <h2>In this document</h2>
22    <ol id="auto-toc">
23    </ol>
24  </div>
25</div>
26
27<p>Audio players support attributes that define how the audio system handles routing, volume, and
28focus decisions for the specified source. Applications can attach attributes to an audio playback
29(such as music played by a streaming service or a notification for a new email) then pass the audio
30source attributes to the framework, where the audio system uses the attributes to make mixing
31decisions and to notify applications about the state of the system.</p>
32
33<p class="note"><strong>Note:</strong> Applications can also attach attributes to an audio
34recording (such as audio captured in a video recording), but this functionality is not exposed in
35the public API.</p>
36
37<p>In Android 4.4 and earlier, the framework made mixing decisions using only the audio stream type.
38However, basing such decisions on stream type was too limiting to produce quality output across
39multiple applications and devices. For example, on a mobile device, some applications (i.e.
40Google Maps) played driving directions on the STREAM_MUSIC stream type; however, on mobile
41devices in projection mode (i.e. Android Auto), applications cannot mix driving directions with
42other media streams.</p>
43
44<p>Using the <a href="http://developer.android.com/reference/android/media/AudioAttributes.html">
45audio attribute API</a>, applications can now provide the audio system with detailed information
46about a specific audio source:</p>
47
48<ul>
49<li><b>Usage</b>. Specifies why the source is playing and controls routing, focus, and volume
50decisions.</li>
51<li><b>Content type</b>. Specifies what the source is playing (music, movie, speech,
52sonification, unknown).</li>
53<li><b>Flags</b>. Specifies how the source should be played. Includes support for audibility
54enforcement (camera shutter sounds required in some countries) and hardware audio/video
55synchronization.</li>
56</ul>
57
58<p>For dynamics processing, applications must distinguish between movie, music, and speech content.
59Information about the data itself may also matter, such as loudness and peak sample value.</p>
60
61<h2 id="using">Using attributes</h2>
62
63<p>Usage specifies the context in which the stream is used, providing information about why the
64sound is playing and what the sound is used for. Usage information is more expressive than a stream
65type and allows platforms or routing policies to refine volume or routing decisions.</p>
66
67<p>Supply one of the following usage values for any instance:</p>
68
69<ul>
70<li><code>USAGE_UNKNOWN</code></li>
71<li><code>USAGE_MEDIA</code></li>
72<li><code>USAGE_VOICE_COMMUNICATION</code></li>
73<li><code>USAGE_VOICE_COMMUNICATION_SIGNALLING</code></li>
74<li><code>USAGE_ALARM</code></li>
75<li><code>USAGE_NOTIFICATION</code></li>
76<li><code>USAGE_NOTIFICATION_RINGTONE</code></li>
77<li><code>USAGE_NOTIFICATION_COMMUNICATION_INSTANT</code></li>
78<li><code>USAGE_NOTIFICATION_COMMUNICATION_DELAYED</code></li>
79<li><code>USAGE_NOTIFICATION_EVENT</code></li>
80<li><code>USAGE_ASSISTANCE_ACCESSIBILITY</code></li>
81<li><code>USAGE_ASSISTANCE_NAVIGATION_GUIDANCE</code></li>
82<li><code>USAGE_ASSISTANCE_SONIFICATION</code></li>
83<li><code>USAGE_GAME</code></li>
84</ul>
85
86<p>Audio attribute usage values are mutually exclusive. For examples, refer to <code>
87<a href="http://developer.android.com/reference/android/media/AudioAttributes.html#USAGE_MEDIA">
88USAGE_MEDIA</a></code> and <code>
89<a href="http://developer.android.com/reference/android/media/AudioAttributes.html#USAGE_ALARM">
90USAGE_ALARM</a></code> definitions; for exceptions, refer to the <code>
91<a href="http://developer.android.com/reference/android/media/AudioAttributes.Builder.html">
92AudioAttributes.Builder</a></code> definition.</p>
93
94<h2 id="content-type">Content type</h2>
95
96<p>Content type defines what the sound is and expresses the general category of the content such as
97movie, speech, or beep/ringtone. The audio framework uses content type information to selectively
98configure audio post-processing blocks. While supplying the content type is optional, you should
99include type information whenever the content type is known, such as using
100<code>CONTENT_TYPE_MOVIE</code> for a movie streaming service or <code>CONTENT_TYPE_MUSIC</code>
101for a music playback application.</p>
102
103<p>Supply one of the following content type values for any instance:</p>
104
105<ul>
106<li><code>CONTENT_TYPE_UNKNOWN</code> (default)</li>
107<li><code>CONTENT_TYPE_MOVIE</code></li>
108<li><code>CONTENT_TYPE_MUSIC</code></li>
109<li><code>CONTENT_TYPE_SONIFICATION</code></li>
110<li><code>CONTENT_TYPE_SPEECH</code></li>
111</ul>
112
113<p>Audio attribute content type values are mutually exclusive. For details on content types,
114refer to the <a href="http://developer.android.com/reference/android/media/AudioAttributes.html">
115audio attribute API</a>.</p>
116
117<h2 id="flags">Flags</h2>
118
119<p>Flags specify how the audio framework applies effects to the audio playback. Supply one or more
120of the following flags for an instance:</p>
121
122<ul>
123<li><code>FLAG_AUDIBILITY_ENFORCED</code>. Requests the system ensure the audibility of the
124sound. Use to address the needs of legacy <code>STREAM_SYSTEM_ENFORCED</code> (such as forcing
125camera shutter sounds).</li>
126<li><code>HW_AV_SYNC</code>. Requests the system select an output stream that supports hardware A/V
127synchronization.</li>
128</ul>
129
130<p>Audio attribute flags are non-exclusive (can be combined). For details on these flags,
131refer to the <a href="http://developer.android.com/reference/android/media/AudioAttributes.html">
132audio attribute API</a>.</p>
133
134<h2 id="example">Example</h2>
135
136<p>In this example, AudioAttributes.Builder defines the AudioAttributes to be used by a new
137AudioTrack instance:</p>
138
139<pre>
140AudioTrack myTrack = new AudioTrack(
141  new AudioAttributes.Builder()
142 .setUsage(AudioAttributes.USAGE_MEDIA)
143    .setContentType(AudioAttributes.CONTENT_TYPE_MUSIC)
144    .build(),
145  myFormat, myBuffSize, AudioTrack.MODE_STREAM, mySession);
146</pre>
147
148<h2 id="compatibility">Compatibility</h2>
149
150<p>Application developers should use audio attributes when creating or updating applications for
151Android 5.0. However, applications are not required to take advantage of attributes; they can
152handle legacy stream types only or remain unaware of attributes (i.e. a generic media player that
153doesn’t know anything about the content it’s playing).</p>
154
155<p>In such cases, the framework maintains backwards compatibility with older devices and Android
156releases by automatically translating legacy audio stream types to audio attributes. However, the
157framework does not enforce or guarantee this mapping across devices, manufacturers, or Android
158releases.</p>
159
160<p>Compatibility mappings:</p>
161
162<table>
163<tr>
164  <th>Android 5.0</th>
165  <th>Android 4.4 and earlier</th>
166</tr>
167<tr>
168  <td>
169  <code>CONTENT_TYPE_SPEECH</code><br>
170  <code>USAGE_VOICE_COMMUNICATION</code>
171  </td>
172  <td>
173  <code>STREAM_VOICE_CALL</code>
174  </td>
175</tr>
176<tr>
177  <td>
178  <code>CONTENT_TYPE_SONIFICATION</code><br>
179  <code>USAGE_ASSISTANCE_SONIFICATION</code>
180  </td>
181  <td>
182  <code>STREAM_SYSTEM</code>
183  </td>
184</tr>
185<tr>
186  <td>
187  <code>CONTENT_TYPE_SONIFICATION</code><br>
188  <code>USAGE_NOTIFICATION_RINGTONE</code>
189  </td>
190  <td>
191  <code>STREAM_RING</code>
192  </td>
193</tr>
194<tr>
195  <td>
196  <code>CONTENT_TYPE_MUSIC</code><br>
197  <code>USAGE_UNKNOWN</code><br>
198  <code>USAGE_MEDIA</code><br>
199  <code>USAGE_GAME</code><br>
200  <code>USAGE_ASSISTANCE_ACCESSIBILITY</code><br>
201  <code>USAGE_ASSISTANCE_NAVIGATION_GUIDANCE</code><br>
202  </td>
203  <td>
204  <code>STREAM_MUSIC</code>
205  </td>
206</tr>
207<tr>
208  <td>
209  <code>CONTENT_TYPE_SONIFICATION</code><br>
210  <code>USAGE_ALARM</code>
211  </td>
212  <td>
213  <code>STREAM_ALARM</code>
214  </td>
215</tr>
216<tr>
217  <td>
218  <code>CONTENT_TYPE_SONIFICATION</code><br>
219  <code>USAGE_NOTIFICATION</code><br>
220  <code>USAGE_NOTIFICATION_COMMUNICATION_REQUEST</code><br>
221  <code>USAGE_NOTIFICATION_COMMUNICATION_INSTANT</code><br>
222  <code>USAGE_NOTIFICATION_COMMUNICATION_DELAYED</code><br>
223  <code>USAGE_NOTIFICATION_EVENT</code><br>
224  </td>
225  <td>
226  <code>STREAM_NOTIFICATION</code>
227  </td>
228</tr>
229<tr>
230  <td>
231  <code>CONTENT_TYPE_SPEECH</code>
232  </td>
233  <td>
234  (@hide)<code> STREAM_BLUETOOTH_SCO</code>
235  </td>
236</tr>
237<tr>
238  <td>
239  <code>FLAG_AUDIBILITY_ENFORCED</code>
240  </td>
241  <td>
242  (@hide)<code> STREAM_SYSTEM_ENFORCED</code>
243  </td>
244</tr>
245<tr>
246  <td>
247  <code>CONTENT_TYPE_SONIFICATION</code><br>
248  <code>USAGE_VOICE_COMMUNICATION_SIGNALLING</code>
249  </td>
250  <td>
251  (@hide)<code> STREAM_DTMF</code>
252  </td>
253</tr>
254</table>
255
256<p class="note"><strong>Note:</strong> @hide streams are used internally by the framework but are
257not part of the public API.</p>