RISCOS_FILE_HANDLING in ka_file.c
---------------------------------

Determines the method used by the application to read the content
of video files.

1) If RISCOS_FILE_HANDLING is #defined

The application uses the RISC OS SWI interface to access video files.
This is currenlty the fastest method.

2) If RISCOS_FILE_HANDLING is not #defined

The application uses the portable standard C library functions to access files.

OS_TIMER in timer1.c
--------------------

Determines the method used by the application to get timing information.

1) If OS_TIMER is #defined

The application uses the standard low resolution (1/100 sec) timer provided
by RISC OS. This is more or less sufficient for the end user but is totally 
useless when profiling operations during the development phase.

2) If OS_TIMER is not #defined

The application uses a modules which uses the HAL layer of the Iyonix
or direct access to the IOC timer1 to provide high resolution (1/100000 sec)
timer. The problem is that the A9Home contains no IOC and its OS doesn't
offer the HAL which means that the application doesn't work on this machine.


YUV_LOOKUP switch in colorspace/colconv.c
-----------------------------------------

The 256-colours display uses a y5u4v4->colour number lookup table
and this build switch controls how this table is built.

1) If YUV_LOOKUP is #defined

In a first step that only needs to be done at startup or if a palette
change occurs, the 256-colours palette is translated to YUV and a normalized
y5u4v4->colour table is built from it by finding the best matching YUV
translated palette colour for each yuv triplet. This process is somewhat slow
but it doesn't really matter since this is a one-shot.

The second step is perform at startup and after any brightness/contrast/colour
level modification. It builds the real lookup table by applying the level
corrections to each yuv triplet and looking in the original table with
the level corrected triplet to find the corresponding colour number.

2) If YUV_LOOKUP is not #defined

In a first step that only needs to be done at startup or if a palette
change occurs, a r4g4b4->colour table is built from it by finding the best
matching RGB palette colour for each rgb triplet.

The second step is perform at startup and after any brightness/contrast/colour
level modification. It builds the real lookup table by applying the level
corrections to each yuv triplet, converting it to an r8g8b8 triplet and
using the r4g4b4->colour table to find the corresponding colour number.

This is the oldest method.

vcodec_cvid.c versus vcodec_cvidr.c
-----------------------------------

Both are Cinepak decoders but one decodes to YUV and the other to RGB.
