我开始qjackctl看到这个：
RT 闪烁，很好。但是没有音频，例如在浏览器中的 YouTube 上。以下是启动时消息窗口中的文本qjackctl
看起来 jack 未运行，因此它启动了它。在运行 qjackctl 之前，我是否需要明确启动 jack（或者最好这样做）？
然后出现了一些错误信息：
Tue Jul 14 17:01:01 2020: ERROR: Cannot lock down 82280346 byte memory area (Cannot allocate memory)
Tue Jul 14 17:01:01 2020: ERROR: control open "hw:USB" (No such device)
Tue Jul 14 17:01:01 2020: ERROR: ALSA: Cannot open PCM device alsa_pcm for capture. Falling back to playback-only mode
Tue Jul 14 17:01:01 2020: ERROR: Cannot use real-time scheduling (RR/10)(1: Operation not permitted)
Tue Jul 14 17:01:01 2020: ERROR: AcquireSelfRealTime error
Cannot lock down 82280346 byte memory area (Cannot allocate memory)
其中任何一个都需要解决吗？
17:04:32.446 Statistics reset.
17:04:32.451 ALSA connection change.
17:04:32.479 D-BUS: Service is available (org.jackaudio.service aka jackdbus).
17:04:32.516 D-BUS: JACK server is starting...
Cannot connect to server socket err = No such file or directory
Cannot connect to server request channel
jack server is not running or cannot be started
JackShmReadWritePtr::~JackShmReadWritePtr - Init not done for -1, skipping unlock
JackShmReadWritePtr::~JackShmReadWritePtr - Init not done for -1, skipping unlock
Cannot connect to server socket err = No such file or directory
Cannot connect to server request channel
jack server is not running or cannot be started
JackShmReadWritePtr::~JackShmReadWritePtr - Init not done for -1, skipping unlock
JackShmReadWritePtr::~JackShmReadWritePtr - Init not done for -1, skipping unlock
17:04:32.539 D-BUS: JACK server was started (org.jackaudio.service aka jackdbus).
Tue Jul 14 17:04:32 2020: Starting jack server...
Tue Jul 14 17:04:32 2020: JACK server starting in realtime mode with priority 10
Tue Jul 14 17:04:32 2020: self-connect-mode is "Don't restrict self connect requests"
Tue Jul 14 17:04:32 2020: ERROR: Cannot lock down 82280346 byte memory area (Cannot allocate memory)
Tue Jul 14 17:04:32 2020: ERROR: control open "hw:USB" (No such device)
Tue Jul 14 17:04:32 2020: Acquired audio card Audio2
Tue Jul 14 17:04:32 2020: creating alsa driver ... hw:PCH|hw:USB|128|2|44100|0|0|nomon|swmeter|-|32bit
Tue Jul 14 17:04:32 2020: ERROR: ALSA: Cannot open PCM device alsa_pcm for capture. Falling back to playback-only mode
Tue Jul 14 17:04:32 2020: configuring for 44100Hz, period = 128 frames (2.9 ms), buffer = 2 periods
Tue Jul 14 17:04:32 2020: ALSA: final selected sample format for playback: 32bit integer little-endian
Tue Jul 14 17:04:32 2020: ALSA: use 2 periods for playback
Tue Jul 14 17:04:32 2020: ERROR: Cannot use real-time scheduling (RR/10)(1: Operation not permitted)
Tue Jul 14 17:04:32 2020: ERROR: AcquireSelfRealTime error
Tue Jul 14 17:04:32 2020: graph reorder: new port 'system:playback_1'
Tue Jul 14 17:04:32 2020: New client 'system' with PID 0
Tue Jul 14 17:04:32 2020: graph reorder: new port 'system:playback_2'
Tue Jul 14 17:04:34 2020: Saving settings to "/home/mickeydog/.config/jack/conf.xml" ...
17:04:34.735 JACK connection change.
17:04:34.736 Server configuration saved to "/home/mickeydog/.jackdrc".
17:04:34.736 Statistics reset.
17:04:34.739 Client activated.
17:04:34.740 Patchbay deactivated.
17:04:34.756 JACK connection graph change.
Cannot lock down 82280346 byte memory area (Cannot allocate memory)
Tue Jul 14 17:04:34 2020: New client 'qjackctl' with PID 3514
-- 编辑 -- 设置输入设备后，出现错误：
Wed Jul 15 07:55:00 2020: ERROR: Cannot lock down 82280346 byte memory area (Cannot allocate memory)
Wed Jul 15 07:55:00 2020: ERROR: Cannot use real-time scheduling (RR/10)(1: Operation not permitted)
Wed Jul 15 07:55:00 2020: ERROR: AcquireSelfRealTime error
关于限制，有一个文件/etc/security/limits.d/audio.conf.disabled包含：
@audio - rtprio 95
@audio - memlock unlimited
#@audio - nice -19
还有一个文件/etc/security/limits.conf，其中所有行都被注释掉，即以#开头
这是启动 PulseAudio 后的系统声音设置。如果 PulseAudio 没有运行，则输出选项卡中没有任何内容。
我尝试过这个：
sudo dpkg-reconfigure -p high jackd
似乎没有效果
通过更改名称，最后 3 个错误被删除audio.conf.disabled：
cd etc/security/limits.d
sudo cp audio.conf.disabled audio.conf
sudo rm audio.conf.disabled
QasMixer：
答案1
qjackctl 之前不需要启动 jackd，但有可能
jackd -d alsa -d hw:0 &您在 qjackctl 高级音频配置中的设置错误：
用于播放的 hw:PCH（这是可以的），但是用于录制的 hw:USB，
hw:USB 不存在:)ERROR: control open "hw:USB" (No such device)：
通常是第一个音频设备hw:0，
第二个音频设备是hw:1
（或者可能是您在保存配置后移除了 USB 设备？）实时调度错误可能是由之前的错误引起的，或者是由于您没有修改用户的 limits.conf，看这里。
Firefox 或 Chrome 没有声音：正常，因为它们使用被禁用的 pulseaudio（我猜）。可以使用 jackd 和 pulseaudio，但首先 jackd 必须没问题。
对于 midi，尝试通过选择每一侧的一个客户端将输入连接到输出，然后单击“连接”