[x264-devel] PSNR Calculation

[James Darnley]

On 11/08/2011, A. Mullius <mullius87 at gmail.com> wrote:
> Hi,
>
> how does the PSNR calculation of x264 work when i use e.g. --video-filter
> resize:width=320,height=240 to encode a 1920x1080 video to 320x240? Does it
> scale the encoded frame up to 1920x1080 or does it scale the original frame
> down to 320x240 for the PSNR calculation? And which interpolation filter is
> used for the rescaling in the PSNR calculation?

The encoder gets the a frame at 320x240 and it uses this to calculate
the psnr.  It never knows about 1920x1080.  The filter uses swscale to
scale the image and uses a bicubic scaler by default.