| 1 | <?xml version='1.0' encoding='UTF-8'?>
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| 2 | <!DOCTYPE topic PUBLIC "-//OASIS//DTD DITA Topic//EN" "topic.dtd">
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| 3 | <topic xml:lang="en-us" id="pcspeaker_passthrough">
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| 4 | <title>PC Speaker Passthrough</title>
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| 5 |
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| 6 | <body>
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| 7 | <p>
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| 8 | As an experimental feature, primarily due to being limited to
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| 9 | Linux host only and unknown Linux distribution coverage,
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| 10 | Oracle VM VirtualBox supports passing through the PC speaker to the
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| 11 | host. The PC speaker, sometimes called the system speaker, is a
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| 12 | way to produce audible feedback such as beeps without the need for
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| 13 | regular audio and sound card support.
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| 14 | </p>
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| 15 | <p>
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| 16 | The PC speaker passthrough feature in Oracle VM VirtualBox handles beeps
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| 17 | only. Advanced PC speaker use by the VM, such as PCM audio, will
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| 18 | not work, resulting in undefined host behavior.
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| 19 | </p>
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| 20 | <p>
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| 21 | Producing beeps on Linux is a very complex topic. Oracle VM VirtualBox
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| 22 | offers a collection of options, in an attempt to make this work
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| 23 | deterministically and reliably on as many Linux distributions and
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| 24 | system configurations as possible. These are summarized in the
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| 25 | following table.
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| 26 | </p>
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| 27 | <table id="table-pcspeaker-config">
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| 28 | <title>PC Speaker Configuration Options</title>
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| 29 | <tgroup cols="3">
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| 30 | <thead>
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| 31 | <row>
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| 32 | <entry>
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| 33 | <p>
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| 34 | <b outputclass="bold">Code</b>
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| 35 | </p>
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| 36 | </entry>
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| 37 | <entry>
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| 38 | <p>
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| 39 | <b outputclass="bold">Device</b>
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| 40 | </p>
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| 41 | </entry>
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| 42 | <entry>
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| 43 | <p>
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| 44 | <b outputclass="bold">Notes</b>
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| 45 | </p>
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| 46 | </entry>
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| 47 | </row>
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| 48 | </thead>
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| 49 | <tbody>
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| 50 | <row>
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| 51 | <entry>
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| 52 | <p>
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| 53 | 1
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| 54 | </p>
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| 55 | </entry>
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| 56 | <entry>
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| 57 | <p>
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| 58 | <filepath>/dev/input/by-path/platform-pcspkr-event-spkr</filepath>
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| 59 | </p>
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| 60 | </entry>
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| 61 | <entry>
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| 62 | <p>
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| 63 | Direct host PC speaker use.
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| 64 | </p>
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| 65 | </entry>
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| 66 | </row>
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| 67 | <row>
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| 68 | <entry>
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| 69 | <p>
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| 70 | 2
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| 71 | </p>
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| 72 | </entry>
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| 73 | <entry>
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| 74 | <filepath>/dev/tty</filepath>
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| 75 | </entry>
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| 76 | <entry>
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| 77 | <p>
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| 78 | Uses the terminal association of the VM process. VM
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| 79 | needs to be started on a virtual console.
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| 80 | </p>
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| 81 | </entry>
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| 82 | </row>
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| 83 | <row>
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| 84 | <entry>
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| 85 | <p>
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| 86 | 3
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| 87 | </p>
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| 88 | </entry>
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| 89 | <entry>
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| 90 | <p><filepath>/dev/tty0</filepath> or
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| 91 | <filepath>/dev/vc/0</filepath>
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| 92 | </p>
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| 93 | </entry>
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| 94 | <entry>
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| 95 | <p>
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| 96 | Can only be used by user <codeph>root</codeph> or
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| 97 | users with <codeph>cap_sys_tty_config</codeph>
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| 98 | capability.
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| 99 | </p>
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| 100 | </entry>
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| 101 | </row>
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| 102 | <row>
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| 103 | <entry>
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| 104 | <p>
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| 105 | 9
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| 106 | </p>
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| 107 | </entry>
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| 108 | <entry>
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| 109 | <p>
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| 110 | A user-specified console or evdev device path.
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| 111 | </p>
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| 112 | </entry>
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| 113 | <entry>
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| 114 | <p>
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| 115 | As for codes 1 to 3, but with a custom device path.
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| 116 | </p>
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| 117 | </entry>
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| 118 | </row>
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| 119 | <row>
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| 120 | <entry>
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| 121 | <p>
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| 122 | 70
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| 123 | </p>
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| 124 | </entry>
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| 125 | <entry>
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| 126 | <p>
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| 127 | <filepath>/dev/tty</filepath>
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| 128 | </p>
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| 129 | </entry>
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| 130 | <entry>
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| 131 | <p>
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| 132 | Standard beep only. Loses frequency and length. See code
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| 133 | 2.
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| 134 | </p>
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| 135 | </entry>
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| 136 | </row>
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| 137 | <row>
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| 138 | <entry>
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| 139 | <p>
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| 140 | 79
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| 141 | </p>
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| 142 | </entry>
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| 143 | <entry>
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| 144 | <p>
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| 145 | A user-specified terminal device path.
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| 146 | </p>
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| 147 | </entry>
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| 148 | <entry>
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| 149 | <p>
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| 150 | As for code 70, but with a custom device path.
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| 151 | </p>
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| 152 | </entry>
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| 153 | </row>
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| 154 | <row>
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| 155 | <entry>
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| 156 | <p>
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| 157 | 100
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| 158 | </p>
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| 159 | </entry>
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| 160 | <entry>
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| 161 | <p>
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| 162 | All of the above.
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| 163 | </p>
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| 164 | </entry>
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| 165 | <entry>
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| 166 | <p>
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| 167 | Tries all the available codes.
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| 168 | </p>
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| 169 | </entry>
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| 170 | </row>
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| 171 | </tbody>
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| 172 | </tgroup>
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| 173 | </table>
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| 174 | <p>
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| 175 | To enable PC speaker passthrough use the following command:
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| 176 | </p>
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| 177 | <pre xml:space="preserve">VBoxManage setextradata <varname>VM-name</varname> "VBoxInternal/Devices/i8254/0/Config/PassthroughSpeaker" <varname>N</varname>
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| 178 | </pre>
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| 179 | <p>
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| 180 | Replace <varname>N</varname> with the code representing
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| 181 | the case you want to use. Changing this setting takes effect when
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| 182 | you next start the VM. It is safe to enable PC speaker passthrough
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| 183 | on all host OSes. It will only have an effect on Linux.
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| 184 | </p>
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| 185 | <p>
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| 186 | The VM log file, <filepath>VBox.log</filepath>, contains lines
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| 187 | with the prefix <codeph>PIT: speaker:</codeph> showing the PC
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| 188 | speaker passthrough setup activities. It gives hints which device
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| 189 | it picked or why it failed.
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| 190 | </p>
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| 191 | <p>
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| 192 | Enabling PC speaker passthrough for the VM is usually the simple
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| 193 | part. The real difficulty is making sure that Oracle VM VirtualBox can
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| 194 | access the necessary device, because in a typical Linux install
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| 195 | most of them can only be accessed by user <codeph>root</codeph>.
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| 196 | You should follow the preferred way to persistently change this,
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| 197 | such as by referring to your distribution's documentation. Since
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| 198 | there are countless Linux distribution variants, we can only give
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| 199 | the general hints that there is often a way to give the X11
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| 200 | session user access to additional devices, or you need to find a
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| 201 | working solution using a udev configuration file. If everything
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| 202 | fails you might try setting the permissions using a script which
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| 203 | is run late enough in the host system startup.
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| 204 | </p>
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| 205 | <p>
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| 206 | Sometimes additional rules are applied by the kernel to limit
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| 207 | access. For example, that the VM process must have the same
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| 208 | controlling terminal as the device configured to be used for
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| 209 | beeping, something which is often very difficult to achieve for
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| 210 | GUI applications such as Oracle VM VirtualBox. The table above contains
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| 211 | some hints, but in general refer to the Linux documentation.
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| 212 | </p>
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| 213 | <p>
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| 214 | If you have trouble getting any beeps even if the device
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| 215 | permissions are set up and VBox.log confirms that it uses evdev or
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| 216 | console for the PC speaker control, check if your system has a PC
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| 217 | speaker. Some systems do not have one. Other complications can
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| 218 | arise from Linux rerouting the PC speaker output to a sound card.
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| 219 | Check if the beeps are audible if you connect speakers to your
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| 220 | sound card. Today almost all systems have one. Finally, check if
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| 221 | the audio mixer control has a channel named "beep", which could be
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| 222 | hidden in the mixer settings, and that it is not muted.
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| 223 | </p>
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| 224 | </body>
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| 225 |
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| 226 | </topic>
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