I am trying to run my Pure Data patch on a Raspberry Pi without a screen.

It runs fine when I attach a display and launch it from the command line.

However if I use the -nogui command line argument, the patch reports:

ALSA input error (snd_pcm_open): Device or resource busy

And I am unable to run it normally without a screen plugged as it reports this error:

Application initialization failed: no display name and no $DISPLAY environment variable

Why does adding -nogui stop the program running? Otherwise what's the best workaround?

Thanks in advance, Slidon

@slidon Hello Slidon......... I don't know why -nogui is a problem but...........
My pi is set up to run "headless" with an x11 vnc server which serves up the same (n=0) desktop so that I can access it from another computer. The server auto-starts when the Pi boots. I can then modify my patches remotely. My Pure Data installation seems quite happy with that........ and runs perfectly......... without a screen, when I am not connected to it (as well).......
If you need help trying that then I will try to did out some links...........
David.

Hi David,

I have installed the x11vnc package am running the server with the command

x11vnc -display :0

Pure Data still gives the same no display error. What command are you using to run x11vnc?

@slidon I run it as an autostart with this file
x11vnc.zip
in the
pi/.config/autostart
folder
The messages that you are getting suggest that you are trying to start pd before the x-session and maybe the x-session is set not to start without the display.
The starting of x probably is invoked in public/user/xinit but editing there is ? dangerous/incomprehensible so maybe you need to invoke public/user/startx at startup and maybe edit it as necessary..
David.

How do you use the Pi without a screen? Via ethernet cable and your computer? In this case you can use an X server (XQuartz for OS X, Xming or MobaXTerm for Windows, Linux has one by default) and use the -X flag with SSH from OS X and Linux, or tick the "Enable X forwarding" in PuTTY on Windows. This way you're letting the Pi to use your computer's X server to display its GUI.

No idea why -nogui stops running. Maybe you can share your patch...

Thanks for replies, I've found a solution.

I am using the xvfb-run command:

xvfb-run pd-extended patch.pd

Which will run the pd-extended command on a virtual display, without returning any errors.

Slidon

In the past for applications where no video was involved I used this:
pd-extended -nogui

I'm using Raspbian Jessie Lite on a Raspberry Pi 3 and as I want to use GEM -nogui is not an option.
At first I thought just a window manager is needed, so I tried various, but all returned something like "can't connect to display".

Finally I installed LXDE: https://www.raspberrypi.org/forums/viewtopic.php?f=66&t=133691
Now I can run pd without problems and get video output at the hdmi port:
sudo startx /usr/bin/pd-extended <...arguments for pd...>
Tricky is that you need to specify the absolute path to pd. If you do not you can't pass any arguments to pd.

Maybe anyone has another (more lightweight) solution which avoids installing LXDE?
OMXplayer for example can output video without LXDE.
Or is it not that easy and some rendering/video-card-communication has to be done by LXDE and isn't built into pd?