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General Philosophy

sound_play ノードは音(built-in, wave file or synthesized text)を繰り返し出したり停止したりすることで，その音を実在しているものとして扱っています．robotsound トピックに publish することで音の状態を変えることができます．多重音を同時に出すこともできます．

Supported Hardware

このノードは PR2 についている Logitech USB speaker や組み込みの Intel sound-cards の一部で動作確認されていますが，SDL のサポート対象である sound card はすべてサポートされるべきです．このノードは pygame で SDL にアクセスするので，どの sound device が使われているかまでは管理できないのです．使いたい sound device を SDL と ALSA/OSS の default に設定する必要があります．

API Stability

• C++ と Python の API は安定です
• ROS API， 特にメッセージフォーマットに関しては信用すべきではありませんし，いつか拡張機能をサポートするよう変化するかもしれません

Known Limitations

これらの制限がどうしても煩わしい場合はお知らせ下さい．

• 同一の音源を別々に使っている2つのノードはおかしな相互作用を引き起こすかもしれません．例えば，片方のノードが停止しようとしたときにもう一方のノードが再生しようとするときなどです．
• 音源が再生をやめたときを知らせるすべはありません．
• 何度も再生されたときは，その音のコピーが同時にキューに最大2つまでたまります．

C++/Python API

C++ と Python が共存する方法は提供されています．C++ や Python から音を再生するときに直接 message を生成する必要はありません．これに関する資料は doxygen (English)にあります．

Command-line utilities

• soundplay_node.py が動いているときに使える便利なものを以下に示していきます．soundplay_node.py に関しては tutorial (English) を参照して下さい．

Playing a .WAV or .OGG file

The play.py script can play any .WAV or .OGG file. The file must be available on the computer on which soundplay_node.py is running, and an absolute path should be given.

$ rosrun sound_play play.py --help
Usage: /u/blaise/ros/ros-pkg/stacks/sound_drivers/sound_play/scripts/play.py sound_to_play.(ogg|wav)

Plays an .OGG or .WAV file. The path to the file should be absolute, and be valid on the computer on which sound_play is running.

For example (soundplay_node.py should be running first):

$rosrun sound_play play.py /usr/share/xemacs21/xemacs-packages/etc/sounds/im_so_happy.wav
Playing "/usr/share/xemacs21/xemacs-packages/etc/sounds/im_so_happy.wav".

Playing a built in sound

Some standard sounds are built-into the driver, and can be played only by specifying their integer identifier using playbuiltin.py.

$ rosrun sound_play playbuiltin.py 
Usage: /u/blaise/ros/ros-pkg/stacks/sound_drivers/sound_play/scripts/playbuiltin.py <sound_id>

Plays one of the built-in sounds based on its integer ID. Look at the <<MsgLink(sound_play/SoundRequest)>> message definition for IDs.

For example (soundplay_node.py should be running first):

$ rosrun sound_play playbuiltin.py 2
Playing sound 2".

To get an up-to-date list of the built-in sounds, consult the definition of the sound_play/SoundRequest message. The relevant information is below the "Sounds" comment.

$ cat `rospack find sound_play`/msg/SoundRequest.msg
# Sounds
byte BACKINGUP = 1
byte NEEDS_UNPLUGGING = 2
byte NEEDS_PLUGGING = 3
byte NEEDS_UNPLUGGING_BADLY = 4
byte NEEDS_PLUGGING_BADLY = 5

# Sound identifiers that have special meaning
byte ALL = -1 # Only legal with PLAY_STOP
byte PLAY_FILE = -2
byte SAY = -3

byte sound # Selects which sound to play (see above)

# Commands
byte PLAY_STOP = 0 # Stop this sound from playing
byte PLAY_ONCE = 1 # Play the sound once
byte PLAY_START = 2 # Play the sound in a loop until a stop request occurs

byte command # Indicates what to do with the sound

string arg # file name or text to say

Saying Some Text

The sound node can also be used to synthesize speech using the festival speech synthesis system. The say.py script gives command-line access to this functionality. This script can take its input from the command line, or if the command-line is empty it can take input from standard input.

$ rosrun sound_play say.py --help
$ rosrun sound_play say.py --help
Usage: /u/blaise/ros/ros-pkg/stacks/sound_drivers/sound_play/scripts/say.py 'String to say.'
       /u/blaise/ros/ros-pkg/stacks/sound_drivers/sound_play/scripts/say.py < file_to_say.txt

Says a string. For a string on the command line, you must use quotes as
appropriate. For a string on standard input, the command will wait for
EOF before saying anything.

Examples (soundplay_node.py should be running first):

$ rosrun sound_play say.py 'Hello world'
Saying: Hello world.
$ echo Hello again|rosrun sound_play say.py
Awaiting something to say on standard input.
Saying: Hello again

Silencing the Robot

The most immediate way to silence the robot is to use alsamixer to mute or lower the volume. In some cases, a node that had requested a continuous sound could crash with the sound still playing. In order to stop that sound the shutup.py script can be used.

The shutup.py script sends a stop command on all sounds every 100ms until it is terminated. This behavior will immediately stop any continuous sounds that were playing, and will cut short any new sounds that are played. It will not completely silence the robot, however, as the first tens of milliseconds of newly requested sounds will be played before they are silenced.

For example:

$ rosrun sound_play shutup.py 
Sending stopall command every 100 ms.
Note: This will not prevent a node that is continuing to issue commands
from producing sound.
Press Ctrl+C to exit.

Testing Sound Play Node Operation

To test that soundplay_node.py is operating correctly, you can use the test.py script. It will play the various built-in sounds, and exercise the .WAV playing and text-to-speech capabilities. To run it:

$ rosrun sound_play test.py

Nodes

soundplay_node.py

soundplay_node.py subscribes to robotsound and plays sounds on the sound card. This node must be running before the command-line utilities described below will work.

Subscribed Topics

robotsound (sound_play/SoundRequest)

• Topic for playing sound.

Published Topics

diagnostics (diagnostic_msgs/DiagnosticArray)

• Reports driver diagnostic information. Detection of a disconnected sound device can only happen when no sounds have been played for a few seconds.

Example Launch File

The following launch file, which starts soundplay_node.py, can be found in soundplay_node.launch:

<launch>
  <node name="soundplay_node" pkg="sound_play" type="soundplay_node.py"/>
</launch>

Message Format

Programmers should use the C++/Python bindings to send messages to robotsound, rather than creating messages themselves. If you need the information in this section for something other than satisfying curiosity, you are probably doing something wrong.

Sound commands are issued to soundplay_node.py via a sound_play/SoundRequest message. Commands define two things: a sound, and what to do with that sound.

The sound is defined by the sound (int) and arg (string) fields of the message, and can be one of four types:

• a built-in sound, identified by its identifier in sound

• a file, identified by PLAY_FILE in sound and the file name (absolute path on the computer running soundplay_node.py) in arg

• some text to be synthesized into speech, identified by SAY in sound and the text in arg

• the wildcard sound, that can only be used when stopping sound, identified by ALL in sound

The action that can be carried out on a sound can be:

• stop playing the sound
• play the sound once (if it is already playing, it will be played again after the current playback ends)
• play the sound continuously

Each message on the robotsound topic will cause a sound to transition between the playing continuously, playing once (or twice) and stopped states. For example, a backing up sound could be initiated by sending a command for a backing up sound to play continuously. When the robot stops backing up, a stop command will stop playback. Likewise, verbal debugging messages could be used by telling a sound to play once. In this case there is no need to stop playing the sound.

The special wildcard sound can be used to stop playback on all sounds.

<<KforgeTracLink(audiocommon audiocommon)>>