[FFmpeg-trac] #10882(undetermined:new): swscale wastefully scales luma during yuv420p -> yuv422p

[FFmpeg]

#10882: swscale wastefully scales luma during yuv420p -> yuv422p
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             Reporter:  Kieran       |                    Owner:  (none)
  Kunhya                             |
                 Type:  defect       |                   Status:  new
             Priority:  normal       |                Component:
                                     |  undetermined
              Version:  unspecified  |               Resolution:
             Keywords:               |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
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Description changed by Kieran Kunhya:

Old description:

> Run any conversion from yuv420p to yuv422p.
>
> Swscale appears to run hscale and vscale on the unscaled luma plane as
> follows:
>
> dst[x] = (src[x] * (2^n)) >> n;
>
> This uses a lot of CPU for no benefit.

New description:

 Run any conversion from yuv420p to yuv422p.

 Swscale appears to run hscale and vscale on the unscaled luma plane as
 follows:

 {{{
 dst[x] = (src[x] * (2^n)) >> n;
 }}}

 This uses a lot of CPU for no benefit.

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Ticket URL: <https://trac.ffmpeg.org/ticket/10882#comment:1>
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