MJPEG Tools Svn

Fixed some nasty and damn subtle bugs causing corruption of the
fast motion compensation data. Took *ages* to pin down...

Found that wretched bug in the the assembler that was
causing weird, rare, random misbehaviour. Guess who
wasn't saving a modified register. Eeeeee-orrrr....

Annoyingly the (whatever it was) random value of an uninitialised
variable was giving *excellent* quantisation bit-allocation.
I'll have to experiment to find it...

Wasted effort - further tuning of motion compensation search. Instad
found my own and compiler bugs and gain .... wow ... and 8% speed-up
for a days work. Should have worked on SSE code for the quantisation
routines.

First compilation of movtar_unify.

Added hierarchical sub-sampling search. Now first search 4*4
and then uses the results of this to seed the 2*2 search.

Needless to say there's MMX/SSE to match.

This commit was manufactured by cvs2svn to create tag 'PreQuad'.

Introduced experimental coefficient magnitude based quantisation/
bit-rate control (so far so good, but early days).

Ported over MMX based contributed to bbmpeg by others
for dct routines for modest speed gain. The idct may be
sub-optimal - the one in the jpeg routines looks better...

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MMX1 code for interpolated distance calculations (added late
as debugging and testing incomplete earlier)

After climbing the wall trying to find one corrupt frame in a huge
.avi I was compressing to MPEG (probably due to a buffer over-run when
the file-server went off and did its own thing for a bit...) I have
now modified readpic.c to give warnings but not crash if a dud frame
is encountered. In this case mpeg2enc now simply re-uses the previous frame to
keep things reasonably invisible.