[Libre-soc-dev] new svp64 page

Lauri Kasanen cand at gmx.com
Sat Dec 12 07:33:33 GMT 2020

On Fri, 11 Dec 2020 18:58:51 +0000
Luke Kenneth Casson Leighton <lkcl at lkcl.net> wrote:

> Lauri can i ask: how common is clamped arithmetic in AV? i think i
> know the answer (very) however in any given algorithm, what percentage
> of operations are clamped?
> if it is "30%" per audio sample then clearly that weighs strongly in
> favour of the extra 2 bits.  if however it is only say 2% then
> honestly we have higher priorities to weigh.

10-20%? Pathological cases higher. But as Jacob says, the clamp width is
always the dest width. Hence why I said to use the dest elwidth for
clamping. Is there any reason why we can't use it?

u16 * u16 = u8 means exactly that. Inputs 16-bit, operation 16-bit,
destination 8-bit. Dest width = clamp width.

- Lauri

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