xref: /external/libvncserver/x11vnc/misc/turbovnc

#
# This work has been (or is hereby) released into the public domain by
# its author, Karl J. Runge <runge (at] karlrunge.com>. This applies worldwide.
# 
# In case this is not legally possible: Karl J. Runge grants anyone the
# right to use this work for any purpose, without any conditions, unless
# such conditions are required by law.
#

INTRO:
------

This is a "patch" to make x11vnc/libvncserver work with TurboVNC:

	http://www.virtualgl.org/About/TurboVNC
	http://www.karlrunge.com/x11vnc/faq.html#faq-turbovnc

It is very experimental/kludgy.  Not all TurboVNC features may be enabled.
We are currently evaluating whether TurboVNC support should be officially
put into x11vnc/libvncserver.

TurboVNC is an optimized VNC for fast refresh rates on fast networks.

It does pretty well on good broadband as well.  But it is not as fast
as regular TightVNC on slow links.


TURBOJPEG:
---------

TurboVNC uses the TurboJPEG library based on a fast proprietary JPEG
implementation.  You will need to download it from the VirtualGL
sourceforge site:

	http://sourceforge.net/project/showfiles.php?group_id=117509&package_id=166100

Either install it or simply unpack the .deb or .rpm file into a directory.

N.B. you can unpack a .deb via 'ar x package.deb' and the extracting
from the data.tar.gz file.  rpm2cpio can be used to unpack .rpm's.


QUICK-START:
------------

For those in a hurry:

  cd x11vnc-x.y.z/x11vnc/misc/turbovnc
  ./apply_turbovnc
  cd ../../..
  env LDFLAGS='-L/DIR -Xlinker --rpath=/DIR' ./configure
  make AM_LDFLAGS='-lturbojpeg'

where you replace /DIR with your directory containing libturbojpeg.so.


PATCHING AND BUILDING:
----------------------

After unpacking your x11vnc-x.y.z.tar.gz tarball cd to the
x11vnc-x.y.z/x11vnc/misc/turbovnc (where this README file is) and from
that directory run:

	./apply_turbovnc

that will modify files in the libvncserver and x11vnc directories above
this directory.  (To undo these changes run: ./undo_turbovnc)  The input
sources, tight.c and turbojpeg.h are from the TurboVNC source package.

After applying, go back to the top level source directory and run:

	env LDFLAGS='-L/path/to/turbojpeg -Xlinker --rpath=/path/to/turbojpeg' ./configure 

where the turbojpeg library is:

	/path/to/turbojpeg/libturbojpeg.so

(change /path/to/turbojpeg to the directory where you installed or
unpacked it.)

If you are not using gnu gcc and gnu linker the options may be a little
different (e.g. -R instead of -Xlinker --rpath).

If you need additional ./configure options or env. var. settings,
add them too.


Next, run this make command:

	make AM_LDFLAGS='-lturbojpeg'

This is a hack and may not always work, if it doesn't edit x11vnc/Makefile
and add '-lturbojpeg' to the LIBS variable.

This should create a binary:

	./x11vnc/x11vnc

that supports VirtualGL's TurboVNC.

You will need a TurboVNC viewer, you can get one here:

	http://sourceforge.net/project/showfiles.php?group_id=117509&package_id=128130

Let us know how it goes.


PERFORMANCE:
------------

Note that x11vnc has to read the display's screen pixels from the
graphics card memory.  This can be slow, e.g. 10 MB/sec.

There is not a big need for graphics card manufacturers to optimize the
read rate; the write rate is the one they optimize greatly.

	http://www.karlrunge.com/x11vnc/#limitations

If you run x11vnc and see lines like this:

    28/02/2009 00:52:07 Autoprobing selected port 5900
    28/02/2009 00:52:07 fb read rate: 10 MB/sec
    28/02/2009 00:52:07 screen setup finished.

you have a typical slow one.

Whereas if you see this:

    28/02/2009 00:54:46 Autoprobing selected port 5900
    28/02/2009 00:54:46 fb read rate: 321 MB/sec
    28/02/2009 00:54:46 fast read: reset wait  ms to: 10
    28/02/2009 00:54:46 fast read: reset defer ms to: 10
    28/02/2009 00:54:46 screen setup finished.

that is very fast.  In such a situation you may want to dial down
x11vnc's delay, e.g.:  -wait 5 -defer 5, or even smaller to push things
out more quickly.

We have only seen it this fast on Linux by using the nvidia proprietary
graphics drivers.  The Xorg drivers are typically slow 10 MB/sec.

It will also be fast if the X server is virtual: Xvfb or Xdummy
since the screen pixels are stored in RAM:

	http://www.karlrunge.com/x11vnc/faq.html#faq-xvfb

And it will be fast if the ShadowFB xorg.conf option is enabled (if the
card supports it.)


The point we are trying to make is that even though TurboVNC uses a
wicked fast JPEG implementation, and cuts out overhead in its attempt to
pump out as many frames per second as it can, if it is slow for x11vnc
to read the screen pixels in the first place then you might not even
notice the TurboVNC speedup.

So TurboVNC+x11vnc will be faster than TightVNC+x11vnc, but if there is
a large overhead/bottleneck from reading the graphics card framebuffer,
then the speedup will be marginal.