uspp

Apply ultra slow/simple postprocessing filter that compresses and decompresses the image at several (or - in the case of 'quality' level 8 - all) shifts and average the results.

The way this differs from the behavior of spp is that uspp actually encodes & decodes each case with libavcodec Snow, whereas spp uses a simplified intra only 8x8 DCT similar to MJPEG.

The filter accepts the following options:

'quality'

Set quality. This option defines the number of levels for averaging. It accepts an integer in the range 0-8. If set to 0, the filter will have no effect. A value of 8 means the higher quality. For each increment of that value the speed drops by a factor of approximately 2. Default value is 3.

'qp'

Force a constant quantization parameter. If not set, the filter will use the QP from the video stream (if available).