[FFmpeg-devel] Merging the fixed point WMA decoder

Michael Giacomelli michael.giacomelli
Wed Nov 28 19:56:43 CET 2007

I'd like to start working on merging the fixed point wma decoder back into
ffmpeg as soon as my other projects permit.  I have some questions about how
to do this:

1)  We don't really have much fixed point transform or dsputil code in
place.  I've written some that works fine for this particular codec, but
inserting it into ffmpeg is unclear to me.  Is it ok to make a
wmaprecision.h file and import it into dsputil.c and elsewhere so that I can
#define the correct function calls there for things like
vector_fmul_reverse, CMUL, etc?  Or should the wma codec somehow overwrite
those function pointers and defines if needed during it's init?

2)  Although most of the codec is pretty easy to make both fixed and fp just
by playing with type defs and redefining what mul(), CMUL, etc does, theres
some parts where it is not.  Is it acceptable to define function_fixed and
function_float for these cases?  Also, it is frequently necessary to rescale
fixed point values in the middle of functions.  Is it acceptable to #define
blocks in and out in the middle of a function?

3)  I made a number of changes to how the codec works in order to better
accommodate slower embedded processors, mostly in the form of using lookup
tables and making better use of memory so that more could be loaded into
small ondie RAM.  As far as I can tell, none decrease the accuracy of the
codec.  Is there any objection to me merging these in as well?

I appreciate any feedback about how this should be done before I begin

Michael Giacomelli

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