Playback Channel: Spice-GTK Reference Manual

## Playback Channel Playback Channel — audio stream for playback |

## Stability Level

Stable, unless otherwise indicated

## Functions

void | spice_playback_channel_set_delay ()

## Properties

guint | min-latency | Read / Write
gboolean | mute | Read / Write
guint | nchannels | Read / Write
gpointer | volume | Read / Write

## Signals

void | playback-data | Run First
void | playback-get-delay | Run First
void | playback-start | Run First
void | playback-stop | Run First

## Types and Values

struct | SpicePlaybackChannel
struct | SpicePlaybackChannelClass

## Object Hierarchy

        GObject
        ╰── SpiceChannel
            ╰── SpicePlaybackChannel

## Includes

    #include <spice-client.h>

## Description

SpicePlaybackChannel class handles an audio playback stream. The audio data is received via “playback-data” signal, and is controlled by the guest with “playback-stop” and “playback-start” signal events.

Note: You may be interested to let the SpiceAudio class play and record audio channels for your application.

## Functions

### spice_playback_channel_set_delay ()

    void
    spice_playback_channel_set_delay (SpicePlaybackChannel *channel,
                                      guint32 delay_ms);

Adjust the multimedia time according to the delay.

#### Parameters

channel | a SpicePlaybackChannel |
delay_ms | the delay in ms |

## Types and Values

### struct SpicePlaybackChannel

    struct SpicePlaybackChannel;

The SpicePlaybackChannel struct is opaque and should not be accessed directly.

### struct SpicePlaybackChannelClass

    struct SpicePlaybackChannelClass {
        SpiceChannelClass parent_class;

        /* signals */
        void (*playback_start)(SpicePlaybackChannel *channel,
                               gint format, gint channels, gint freq);
        void (*playback_data)(SpicePlaybackChannel *channel, gpointer *data, gint size);
        void (*playback_stop)(SpicePlaybackChannel *channel);
    };

Class structure for SpicePlaybackChannel.

#### Members

`playback_start` () | Signal class handler for the “playback-start” signal. |
`playback_data` () | Signal class handler for the “playback-data” signal. |
`playback_stop` () | Signal class handler for the “playback-stop” signal. |

## Property Details

### The `“min-latency”` property

      “min-latency”              guint

Playback min buffer size (ms).

Owner: SpicePlaybackChannel

Flags: Read / Write

Default value: 200

### The `“mute”` property

      “mute”                     gboolean

Mute.

Owner: SpicePlaybackChannel

Flags: Read / Write

Default value: FALSE

### The `“nchannels”` property

      “nchannels”                guint

Number of Channels.

Owner: SpicePlaybackChannel

Flags: Read / Write

Allowed values: <= 255

Default value: 2

### The `“volume”` property

      “volume”                   gpointer

Playback volume.

Owner: SpicePlaybackChannel

Flags: Read / Write

## Signal Details

### The `“playback-data”` signal

    void
    user_function (SpicePlaybackChannel *channel,
                   gpointer              data,
                   int                   data_size,
                   gpointer              user_data)

Provide audio data to be played.

#### Parameters

channel | the SpicePlaybackChannel that emitted the signal |
data | pointer to audio data |
data_size | size in byte of `data` |
user_data | user data set when the signal handler was connected. |

Flags: Run First

### The `“playback-get-delay”` signal

    void
    user_function (SpicePlaybackChannel *channel,
                   gpointer              user_data)

Notify when the current playback delay is requested

#### Parameters

channel | the SpicePlaybackChannel that emitted the signal |
user_data | user data set when the signal handler was connected. |

Flags: Run First

### The `“playback-start”` signal

    void
    user_function (SpicePlaybackChannel *channel,
                   int                   format,
                   int                   channels,
                   int                   rate,
                   gpointer              user_data)

Notify when the playback should start, and provide audio format characteristics.

#### Parameters

channel | the SpicePlaybackChannel that emitted the signal |
format | a SPICE_AUDIO_FMT |
channels | number of channels |
rate | audio rate |
latency | minimum playback latency in ms |
user_data | user data set when the signal handler was connected. |

Flags: Run First

### The `“playback-stop”` signal

    void
    user_function (SpicePlaybackChannel *channel,
                   gpointer              user_data)

Notify when the playback should stop.

#### Parameters

channel | the SpicePlaybackChannel that emitted the signal |
user_data | user data set when the signal handler was connected. |

Flags: Run First

## See Also

SpiceChannel, and SpiceAudio