Difference between revisions of "GAUDIO"
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== Record == | == Record == | ||
Revision as of 01:38, 4 July 2014
The GAUDIO module provides high level API for handling audio in- and output. The module provides built-in decoders but does also allow to use external codecs. See #External decoder.
Several drivers are provided to play and record data through different hardware peripherals. Any thing from a simple PWM output up to an external codec is supported.
Contents
API reference
The API reference of the GAUDIO module can be found here.
Board file
The GAUDIO module requires a board file to communicate with the hardware. One board file is needed for audio output and one for audio input. See board file.
GDataBuffer
GDataBuffer is the container that is used to hold, manipulate and pass audio data. The buffer is provided and handled by the GQUEUE module. For more information, see GQUEUE#Buffer.
Play back
Before any audio can be played, the audio device has to be initialized using gaudioPlayInit(). Both, the sample format and the sample frequency are set by this function call.
After successful initialization, gaudioPlay() can be used to output audio data. The function takes a pointer to a GDataBuffer that holds the audio data to play in the format that has been set by the initialization call.
gaudioPause() can be used to pause any current audio output. Resuming after a pause is done calling gaudioPlay() without any sample buffer reference.
Calling gaudioStop() will completely stop a current audio playback.
gaudioPlayWait() is used to make sure that the playback is complete. The function will poll for the given timeout (parameter) and return TRUE as soon as nothing is playing anymore or FALSE as soon as the timeout is exceeded.
Volume
The playback volume can be adjusted using gaudioSetVolume(). However, not every driver might implement this feature. The function will return FALSE in that case.
For stereo devices, both channels are set to the same volume.
External decoder
If your audio output devices does have an internal processor to decode audio formats, use GAUDIO_PLAY_FORMAT_FILE as the third parameter for gaudioPlayInit(). The GAUDIO module will simply pass the audio data unmodified to the audio device.
GEVENT integration
The GAUDIO module can optionally be configured to send events through the GEVENT module. This feature is enabled by calling gaudioRecordGetSource(), the GAUDIO module will send the following events:
| Event | Description |
|---|---|
| GAUDIO_PLAY_PLAYING | The audio output system has started to play. |
| GAUDIO_PLAY_FREEBLOCK | An audio buffer has been free'd. |
| GAUDIO_PLAY_LOSTEVENT | The last audio play event was lost. |
Record
ToDo
