Enhanced ComparingUpdateTracker to crop changed blocks
64x64 changed block can be large for fine changes such as cursor
movement and typing in terminal windows, or an update to a clock.
If the block can be efficiently cropped, this will reduce latency
and bandwidth. Every pixel cropped is a pixel less to analyze, encode,
transmit, and decode.
The previous code already detected the top of the change in order
to determine if the block had changed. However, it did not use
this information to reduce the size of the change rectangle, nor
did it calculate any of the other edges.
The new code introduces detection of the other edges, and uses
the information to build a reduced area change rectangle. This
has the additional effect of reducing the number of discrete pixel
values in the change block which may allow a more efficient
encoding algorithm to be selected.
As this section of code is performance sensitive, the method
of detecting the edges has been optimized to quickly fall back
to pessimistic values as soon as a single comparison fails on
each edge. In the case that full 64x64 block are changing,
there will be three extra comparisons per block.
In cases where the change rectangle can be reduced from 64x64,
the reduced size of the change rectangle represents reduced
effort to encode, transfer, and decode the contained pixels.
In the case of images with high frequency changes, which
specifically includes text, the lossy JPEG encoding can be
highly distorted, especially with JPEG level 6 or less. The
quick flash from a distorted JPEG to a lossless JPEG can
appear as a flickering to some people. This effect was more
obvious when the surrounding area is not expected to change,
but is being distorted anyways due to being part of the 64x64
blocking algorithm.
In the case of a user typing in a terminal window, this change
may commonly reduce the number of pixels updated with every
character typed from 4096 pixels (64x64) to 640 pixels (32x20)
or less.
The block size for the comparing update tracker was inefficently low. Raising
it from 16 to 64 pixels significantly reduces the CPU overhead in many cases,
without sacrificing much in what it detects.
git-svn-id: svn://svn.code.sf.net/p/tigervnc/code/trunk@4810 3789f03b-4d11-0410-bbf8-ca57d06f2519
Make the comparing update tracker a bit more flexible. It can now be in an
"auto" state where it will be enabled until we deem that the client is better
of without it (currently triggered by explicitly stating a low compression
level).
git-svn-id: svn://svn.code.sf.net/p/tigervnc/code/trunk@4809 3789f03b-4d11-0410-bbf8-ca57d06f2519
The CopyRect encoding is very efficient so it is wasteful to check those
areas here. It also makes the CUT counter-productive in some cases as it
tends to expand small changes to BLOCK_SIZE (16 pixels) because of the copy
regions.
git-svn-id: svn://svn.code.sf.net/p/tigervnc/code/trunk@4788 3789f03b-4d11-0410-bbf8-ca57d06f2519
Remove the "video" feature and its associated custom JPEG handling.
Having the client specifiy the video region is conceptually wrong
and a problem like this should be handled by better encoding selection.
git-svn-id: svn://svn.code.sf.net/p/tigervnc/code/trunk@3635 3789f03b-4d11-0410-bbf8-ca57d06f2519
[Refactoring] Improved rdr::Exception constructor. It now accepts variable
number of arguments.
[Bugfix] Minor compilation fixes (missing #includes)
git-svn-id: svn://svn.code.sf.net/p/tigervnc/code/trunk@3168 3789f03b-4d11-0410-bbf8-ca57d06f2519
min and max changed to vncmin and vncmax. This solves many problems: Some platforms predefines or redefines these symbols. Some platforms have header files which chokes if min or max are defined.
Mark Mielke
Pierre Ossman
Adam Tkac
Constantin Kaplinsky
Peter Åstrand