用BlueZ A2DP Profile播放音乐

Bluetooth支持两种Profiles来播放音乐，分别是HSP和A2DP。HSP(handset profile)是单声道的，A2DP是双声道的。本文主要介绍如何在Linux下用A2DP来播放音乐。

准备

1. 一个蓝牙耳机和一台Linux机器，Linux上默认会安装BlueZ和PulseAudio。

2. 下载一段时间较长的wav格式的音频文件，测试时会用到。

3. 确保你的蓝牙耳机和PC已经配对成功。如果没有的话，可以通过bluetooth-applet界面查找耳机并配对。

配置

1. 在/etc/pulse/default.pa，注释掉以下两行

bluetooth-discover
module-suspend-on-idle

2.  播放一段较长的wav格式音乐。

paplay 75.wav

3. 用pacmd查看该input的index，在下面的例子中index是2。

xxx@xxx:~/$ pacmd
>>> list-sink-inputs
1 sink input(s) available.
    index: 2
    driver:
    flags:
    state: RUNNING
    sink: 1
    volume: 0: 100% 1: 100%
            0: 0.00 dB 1: 0.00 dB
            balance 0.00
    muted: no
    current latency: 1997.28 ms
    requested latency: 39.51 ms
    sample spec: aLaw 2ch 44100Hz
    channel map: front-left,front-right
                 Stereo
    resample method: copy
    module: 7
    client: 6
    properties:
        media.format = "WAV (Microsoft)"
        application.name = "paplay"
        media.name = "75.wav"
        native-protocol.peer = "UNIX socket client"
        native-protocol.version = "16"
        application.process.id = "6509"
        application.process.user = "xxx"
        application.process.host = "xxx-host"
        application.process.binary = "pacat"
        application.language = "en_US.utf8"
        window.x11.display = ":0.0"
        application.process.machine_id = "aed85c03e5ef20ad3d980db14b34d474"
        application.process.session_id = "aed85c03e5ef20ad3d980db14b34d474-1283675281.437759-895707289"
        module-stream-restore.id = "sink-input-by-application-name:paplay"

4. 用test-audio脚本连接耳机。在下面的例子中，耳机的地址（bdaddr）是00:16:44:21:8D:91。

cd bluez/test;

~bluez/test$ ./test-audio connect 00:16:44:21:8D:91

5. 在pulseaudio console下load module-bluetooth-device模块

>>> load-module module-bluetooth-device profile="a2dp" address="00:16:44:21:8D:91"

在上面的例子中，我们用了A2DP profile加载bluetooth模块，要使用hsp的话，替换参数成profile=”hsp”即可。

6. 在pulseaudio console下list-sink，能够显示出bluetooth的device来。在下面的例子中，index是1。

>>>list-sinks
    index: 1
    name:
    driver:
    flags: HARDWARE DECIBEL_VOLUME LATENCY
    state: RUNNING
    suspend cause:
    priority: 9030
    volume: 0:   7% 1:   7%
            0: -70.57 dB 1: -70.57 dB
            balance 0.00
    base volume: 100%
                 0.00 dB
    volume steps: 65537
    muted: no
    current latency: 44.27 ms
    max request: 2 KiB
    max rewind: 0 KiB
    monitor source: 2
    sample spec: s16le 2ch 44100Hz
    channel map: front-left,front-right
                 Stereo
    used by: 1
    linked by: 1
    fixed latency: 39.51 ms
    card: 1
    module: 16
    properties:
        bluetooth.protocol = "a2dp"
        device.description = "DELL BH200"
        device.string = "00:16:44:21:8D:91"
        device.api = "bluez"
        device.class = "sound"
        device.bus = "bluetooth"
        device.form_factor = "headset"
        bluez.path = "/org/bluez/5373/hci0/dev_00_16_44_21_8D_91"
        bluez.class = "0x640404"
        bluez.name = "DELL BH200"
        device.icon_name = "audio-headset-bluetooth"

7. 在pulseaudio console下，用move-sink-input 即可将声音导到蓝牙耳机上。

>>> move-sink-input 2 1

好了，你应该能从蓝牙耳机上听到音乐了。；-）