[FFmpeg-devel] [PATCH 0/2] Remove float_to_int16 add bias hack

[Justin Ruggles]

I'm not convinced that the hack in DSPContxt.float_to_int16 where
the C version has a different scale and bias than the SIMD versions
is really needed.  The addition still has to be done somewhere.
In most cases this seems to be in vector_fmul_window(), and in other
cases it's just a completely separate loop over the samples to add
the bias that would otherwise not be needed.  For the
vector_fmul_window() cases, the add bias in that function is ONLY
there because of the C version of float_to_int16.  And if a system
has to use a C version of float_to_int16, likely it also has to use
the C version of vector_fmul_window() and there is no net gain.

Anyway, here is a patch to make float_to_int16() always take input
in the range [-32768.0,32767.0], removing the need for the add bias.
The scaling could still be useful in the future though if those
decoders are modified to give float output instead of int16. It
would be nice to still have the flexibility to change the scale of
the output float samples per user request without additional
overhead.

This patch does not address the 3 asm functions that will no longer
need the bias parameter.  I just don't feel comfortable enough
with modifying the ARM versions myself.
SynthFilterContext.synth_filter_float()
DCADSPContext.lfe_fir()
DSPContext.vector_fmul_window()

Cheers,
Justin

Justin Ruggles (2):
  Remove the add bias hack for the C version of
    DSPContext.float_to_int16_*().
  cosmetics: indentation and spacing

 libavcodec/aac.h           |    1 -
 libavcodec/aacdec.c        |   46 +++++++++++++---------------------
 libavcodec/aacsbr.c        |   13 ++-------
 libavcodec/ac3dec.c        |   17 +++----------
 libavcodec/ac3dec.h        |    1 -
 libavcodec/binkaudio.c     |    5 ----
 libavcodec/dca.c           |   58 ++++++++++++++++++-------------------------
 libavcodec/dsputil.c       |    9 +------
 libavcodec/dsputil.h       |    3 +-
 libavcodec/nellymoserdec.c |   11 +-------
 libavcodec/wmadec.c        |   29 +++++----------------
 11 files changed, 60 insertions(+), 133 deletions(-)