0
# Device I/O
1

2
Device enumeration and access for cameras, microphones, and other multimedia input/output devices across platforms using FFmpeg's libavdevice.
3

4
## Capabilities
5

6
### Device Enumeration
7

8
#### Device Discovery
9

10
```java { .api }
11
/**
12
 * List devices for input format
13
 * @param s Format context
14
 * @param device_list Pointer to receive device list
15
 * @return >= 0 on success
16
 */
17
int avdevice_list_devices(AVFormatContext s, AVDeviceInfoList device_list);
18

19
/**
20
 * List input sources for device
21
 * @param device Input format
22
 * @param device_name Device name (optional)
23
 * @param device_options Device options (optional)
24
 * @param device_list Pointer to receive device list
25
 * @return >= 0 on success
26
 */
27
int avdevice_list_input_sources(AVInputFormat device, String device_name,
28
    AVDictionary device_options, AVDeviceInfoList device_list);
29

30
/**
31
 * List output sinks for device
32
 * @param device Output format
33
 * @param device_name Device name (optional)
34
 * @param device_options Device options (optional)
35
 * @param device_list Pointer to receive device list
36
 * @return >= 0 on success
37
 */
38
int avdevice_list_output_sinks(AVOutputFormat device, String device_name,
39
    AVDictionary device_options, AVDeviceInfoList device_list);
40

41
/**
42
 * Free device list
43
 * @param device_list Device list to free
44
 */
45
void avdevice_free_list_devices(AVDeviceInfoList device_list);
46
```
47

48
**Usage Example:**
49

50
```java
51
import org.bytedeco.ffmpeg.avdevice.*;
52
import org.bytedeco.ffmpeg.avformat.*;
53
import static org.bytedeco.ffmpeg.global.avdevice.*;
54
import static org.bytedeco.ffmpeg.global.avformat.*;
55

56
// Initialize device library
57
avdevice_register_all();
58

59
// Find video4linux2 input format (Linux)
60
AVInputFormat v4l2Format = av_find_input_format("v4l2");
61
if (v4l2Format != null) {
62
    AVDeviceInfoList deviceList = new AVDeviceInfoList();
63
    int result = avdevice_list_input_sources(v4l2Format, null, null, deviceList);
64
    
65
    if (result >= 0) {
66
        System.out.println("Found " + deviceList.nb_devices() + " video devices:");
67
        for (int i = 0; i < deviceList.nb_devices(); i++) {
68
            AVDeviceInfo device = deviceList.devices(i);
69
            System.out.println("Device: " + device.device_name().getString());
70
            System.out.println("Description: " + device.device_description().getString());
71
        }
72
        avdevice_free_list_devices(deviceList);
73
    }
74
}
75
```
76

77
### Device Opening
78

79
#### Device Access
80

81
```java { .api }
82
/**
83
 * Register all device formats
84
 */
85
void avdevice_register_all();
86

87
/**
88
 * Send control message to device
89
 * @param s Format context
90
 * @param type Message type
91
 * @param data Message data
92
 * @param data_size Data size
93
 * @return >= 0 on success
94
 */
95
int avdevice_dev_to_app_control_message(AVFormatContext s, int type, Pointer data, long data_size);
96

97
/**
98
 * Receive control message from device
99
 * @param s Format context
100
 * @param type Message type
101
 * @param data Message data
102
 * @param data_size Data size
103
 * @return >= 0 on success
104
 */
105
int avdevice_app_to_dev_control_message(AVFormatContext s, int type, Pointer data, long data_size);
106
```
107

108
### Platform-Specific Devices
109

110
#### Common Device Names
111

112
```java { .api }
113
// Linux (Video4Linux2)
114
"v4l2"          // Video capture devices
115
"alsa"          // Audio capture/playback
116
"pulse"         // PulseAudio
117

118
// Windows
119
"dshow"         // DirectShow devices
120
"gdigrab"       // Screen capture
121
"wasapi"        // Windows Audio Session API
122

123
// macOS
124
"avfoundation"  // AVFoundation devices
125
"qtkit"         // QuickTime Kit (deprecated)
126

127
// Cross-platform
128
"lavfi"         // Libavfilter virtual devices
129
"sdl"           // SDL output
130
```
131

132
## Data Structures
133

134
### Device Information
135

136
```java { .api }
137
/**
138
 * Device information structure
139
 */
140
class AVDeviceInfo extends Pointer {
141
    /** Device name/identifier */
142
    BytePointer device_name();
143
    
144
    /** Human-readable description */
145
    BytePointer device_description();
146
    
147
    /** Media types supported */
148
    IntPointer media_types();
149
    
150
    /** Number of media types */
151
    int nb_media_types();
152
}
153

154
/**
155
 * List of devices
156
 */
157
class AVDeviceInfoList extends Pointer {
158
    /** Array of device info */
159
    PointerPointer devices();
160
    
161
    /** Number of devices */
162
    int nb_devices();
163
    
164
    /** Default device index */
165
    int default_device();
166
}
167
```
168

169
## Constants
170

171
### Device Types
172

173
```java { .api }
174
// Media types for devices
175
int AVMEDIA_TYPE_VIDEO = 0;      // Video devices
176
int AVMEDIA_TYPE_AUDIO = 1;      // Audio devices
177
int AVMEDIA_TYPE_DATA = 2;       // Data devices
178
```