[Ffmpeg-devel] VP3/Theora Perfection
Tue May 17 20:39:45 CEST 2005
On Tuesday 17 May 2005 18:52, Mike Melanson wrote:
> >>> Why? Dequantization is a parallelizable operation that can be optimized
> >>>with SIMD instructions. That is why it is done at the same time as the
> >>>optimized IDCTs.
> >>i prefer to multiply 2 elements without SIMD over multiplying 64 with
> >> SIMD
> > :)
> Okay, so I'm really confused now. There are 64 DCT coefficients. All 64
> need to be dequantized. That means you have to do 64 multiplications.
> Where do you come up with the "multiply 2 elements", smart guy(s)? Are
> you talking about optimizations like checking for 0-value coeffs during
> the decode process and skipping the mult.?
well, you dont have to check for 0 during decode, as zeros are already handled
differntly, its just fetching the right value from the quantization table and
doing the dequant
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