video does not work on linux:
http://processing.org/reference/libraries/video/

As I mentioned before, I'm trying to use my digital camcorder as a webcam with processing(+GSvideo), in linux.

I'm stuck, and not really sure how to progress, so I thought I'd spell out my experience so far - in case anyone has any ideas or wants info on achieving the same.

There's a utility called dv4l(http://dv4l.berlios.de/) which can be used to create an interface between the dvcam and video4linux (v4l).

dv4l can can be used in two different ways;

1. via a utility called 'dv4lstart'
2. via a utility called 'dv4l' + a module called 'vloopback' (http://www.lavrsen.dk/twiki/bin/view/Motion/VideoFourLinuxLoopbackDevice )



Method 1;
---------

This should be the simplest route...

run 'dv4lstart ./processing'  

The idea here is to use dv4lstart to create a v4l device at '/dev/video0'; and then load processing, allowing it to make use of the new device.  In theory, the camera negotiations should be invisible to processing (and GSvideo) and all should work well... but, I get an error when I run the command..

# An unexpected error has been detected by HotSpot Virtual Machine:
#
#  SIGBUS (0x7) at pc=0xb78b0b0a, pid=15828, tid=3084363440
#
# Java VM: Java HotSpot(TM) Client VM (1.5.0_12-b04 mixed mode, sharing)
# Problematic frame:
# V  [libjvm.so+0x313b0a]
#
# An error report file with more information is saved as hs_err_pid15828.log
#
# If you would like to submit a bug report, please visit:
#   http://java.sun.com/webapps/bugreport/crash.jsp

.. so I've had to abandon this idea.  I've successfully managed to load other programs (vlc and camorama) using dv4lstart... so the problem is something specific to processing and/or java.



Method 2;
---------

This route's a little more complicated.  I've divided it into two attempts

ATTEMPT 1;

i) load vloopback by running 'sudo modprobe vloopback'
This will create two devices at /dev/video0 and /dev/video1.  The first is used for video input and the second is used for video output.

ii) run 'dv4l'
This command streams the video from the camcorder (which will then be accessible using v4l at '/dev/video1').  

At this point I thought I was onto something, but I still had a problem ... I need the video to be accessible at '/dev/video0' NOT '/dev/video1'.  After hours of hopelessness, I found that vloopback can take a parameter;

ATTEMPT 2;

i)run 'sudo modprobe vloopback dev_offset=1'
This will create two devices at /dev/video1 and /dev/video2 (crucially, leaving '/dev/video0' unused).  

ii)run 'dv4l'
This is just the same as before .. only now the v4l device will be '/dev/video2'.  
I assumed that I would then be able to finish off the bastard, with a symbolic link;

iii)'sudo ln -s /dev/video2 /dev/video0

Now, I'm no linux expert at all, and all of what I know is cobbled together.. but I believed that this should have worked - and I'm confused to why it hasn't.  If you've read to this point, thanks for baring with me.

Any ideas would be amazing.

Hi

I've tried out a couple of the examples (my v4l device is '/dev/video1')

eg.  in Mirror, I swapped..

Code:

video = new GSCapture(this, width, height, 12);
 

for..

Code:

video = new GSCapture(this, width, height, new String[] {"device"}, new String[] {"/dev/video1"});
 

Unfortunately I get a blank screen...  am I using the updated code in the right way?

dv4l does use v4l (rather than v4l2)...
I tried the modified code - but no luck... does gsvideo require a particular type of stream?  yuv / rgb ..??

I didn't know about gst-launch... I now know that the problem is definitely with gstreamer.

----

I pretty much know that dv4l is doing _something_ because videolan is playing the stream produced at /dev/video1, without any problem...

Running..
Code:

gst-launch --gst-debug-level=0 v4lsrc device=/dev/video1
 

produces..
Code:

Setting pipeline to PAUSED ...
ERROR: Pipeline doesn't want to pause.
ERROR: from element /pipeline0/v4lsrc0: Could not negotiate format
Additional debug info:
gstbasesrc.c(2359): gst_base_src_start (): /pipeline0/v4lsrc0:
Check your filtered caps, if any
Setting pipeline to NULL ...
FREEING pipeline ...
 

So maybe I need to parse some more parameters to gstreamer to solve the Code:

ERROR: from element /pipeline0/v4lsrc0: Could not negotiate format 

error??

If I work out what's required to get gstreamer working with dv4l, I'll post the results here

cheers

luke

Yes, that pipe can certainly be created inside gsvideo.

I'm just thinking of a general way to do it. Perhaps I could add a new class called GSCustom or something like that where you can specify any pipeline you want, and gsvideo will create it. For example:

String pipe[] = { "dv1394src",  "queue", "dvdemux" "ffdec_dvvideo", "ffmpegcolorspace (video/x-raw-yuv, width=720" };
capture = new GSCustom(pipe);

where the input array contains each element that defines the pipeline (and caps between parenthesis).

Or even simpler:

capture = new GSCustom("dv1394src | queue | dvdemux | ffdec_dvvideo | ffmpegcolorspace video/x-raw-yuv, width=720");

All of this is fairly easy to implement. Internally, gsvideo would add a buffer grabber to direct frames to the processing canvas, instead of using xvimagesink.

What interface you think would be better? Or this possibility of defining custom pipes should be as a part of GSCapture? Personally, I think it would be better if custom pipes are handled by a separate object.

Check out this new version of the library:

http://users.design.ucla.edu/~acolubri/processing/gsvideo/gsvideo-lib-customtest.zip

I wrote a little example (Examples/Custom/dv1934src) using the pipeline you are trying out. Let me know how it goes.