我有两台电脑，它们的 manjaro 安装非常相似。两者都安装了相同的 jack2、QJackCtl 和内核版本。
电脑1台
这是有效的：
我可以启动杰克并听到 lmms 和 Hydrogen 中的东西。然后，pulseaudio 的其他音频输出将停止，这是预料之中的。当在 QJackCtl 中停止和启动 jack 时，它看起来像这样：
01:01:48.817 Client deactivated.
01:01:48.827 JACK is stopping...
Jack main caught signal 15
Released audio card Audio0
audio_reservation_finish
01:01:49.074 JACK was stopped
01:01:51.610 JACK is starting...
01:01:51.611 /usr/bin/jackd -dalsa -dhw:0 -r48000 -p1024 -n2
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
01:01:51.652 JACK was started with PID=1969.
Cannot create RT messagebuffer thread: Operation not permitted (1)
Retrying messagebuffer thread without RT scheduling
Messagebuffer not realtime; consider enabling RT scheduling for user
no message buffer overruns
Cannot create RT messagebuffer thread: Operation not permitted (1)
Retrying messagebuffer thread without RT scheduling
Messagebuffer not realtime; consider enabling RT scheduling for user
no message buffer overruns
Cannot create RT messagebuffer thread: Operation not permitted (1)
Retrying messagebuffer thread without RT scheduling
Messagebuffer not realtime; consider enabling RT scheduling for user
no message buffer overruns
jackdmp 1.9.14
Copyright 2001-2005 Paul Davis and others.
Copyright 2004-2016 Grame.
Copyright 2016-2019 Filipe Coelho.
jackdmp comes with ABSOLUTELY NO WARRANTY
This is free software, and you are welcome to redistribute it
under certain conditions; see the file COPYING for details
JACK server starting in realtime mode with priority 10
self-connect-mode is "Don't restrict self connect requests"
Cannot lock down 82280346 byte memory area (Cannot allocate memory)
audio_reservation_init
Acquire audio card Audio0
creating alsa driver ... hw:0|hw:0|1024|2|48000|0|0|nomon|swmeter|-|32bit
configuring for 48000Hz, period = 1024 frames (21.3 ms), buffer = 2 periods
ALSA: final selected sample format for capture: 32bit integer little-endian
ALSA: use 2 periods for capture
ALSA: final selected sample format for playback: 32bit integer little-endian
ALSA: use 2 periods for playback
Cannot use real-time scheduling (RR/10) (1: Operation not permitted)
AcquireSelfRealTime error
01:01:53.832 JACK connection change.
01:01:53.834 Server configuration saved to "/home/mango/.jackdrc".
01:01:53.835 Statistics reset.
01:01:53.866 Client activated.
01:01:53.867 Patchbay deactivated.
01:01:53.882 JACK connection graph change.
Cannot lock down 82280346 byte memory area (Cannot allocate memory)
电脑2
在此情况下，所有pulseaudio 应用程序将继续播放声音，lmms 和Hydrogen 则不会。当在 QJackCtl 中停止和启动 jack 时，我看到的就是：
00:52:35.422 Client deactivated.
00:52:36.599 JACK connection change.
00:52:36.618 Client activated.
00:52:36.619 Patchbay deactivated.
Cannot lock down 82280346 byte memory area (Cannot allocate memory)
正如您所看到的，它没有记录太多东西。
在此处插入/usr/bin/jackd -dalsa -dhw:0 -r48000 -p1024 -n2来自工作机的命令会产生：
`default' server already active
Failed to open server
如果我在重新启动后或使用后直接运行相同的命令jack_control stop，则会产生：
audio_reservation_init
Acquire audio card Audio0
creating alsa driver ... hw:0|hw:0|1024|2|48000|0|0|nomon|swmeter|-|32bit
ALSA: Cannot open PCM device alsa_pcm for playback. Falling back to capture-only mode
Released audio card Audio0
audio_reservation_finish
Cannot initialize driver
JackServer::Open failed with -1
Failed to open server
同样适用于jackd -d alsa
PCM 错误消息不会出现在计算机 1 上。
在两台机器上，QJackCtl 声称 Jack 处于“活动”状态
哪里可以继续寻找问题呢？
谢谢
答案1
根本没有音频播放的解决方案是检查 QJackCtl 中的输出设备
Setup...-> Settings-> Advanced->Output Device
并将其设置到我的声卡。