How to use parameter arnr-maxframe in VP9 ?

[Fostwer David]

hi ,

 Do any know the meaning of VP9 parameter arnr-maxframe  ?

I don't when we need to set or what's the purpose ?

Do someone know ?

Thanks

The official  explaination is as below:
However, many other options are possible and one alternative that has been implemented uses a temporally filtered image derived from a group of future frames. The extra control parameters for this are:

--arnr-maxframes=<arg>           (number of frames to filter over 0-25)

[Adrian Grange]

Hi David,

In VP9 (and VP8) we have the Alternate Reference Frame (ARF), a (usually) non-displayable frame that is encoded into the bitstream and used purely as an alternative reference buffer.

Whilst VP[8|9] allows this frame to contain arbitrary data the current vpxenc encoder chooses to encode one of two possible ARF frames:

(1) A forward reference frame, i.e. a frame encoded out-of-order ahead of its usual timestamp,

(2) A filtered reference frame, the result of applying a non-linear temporal filter to N future frames.

In the latter case, the encoder uses what we call Alternative Reference Noise Reduction (ARNR) filtering to produce the ARF from a number of future input frames. The parameter arnr-maxframe defines how many frames to filter to produce the ARF frame. This number may be reduced internally, for example, to stop the filtering extending beyond a keyframe.

There are two related parameters:

-- arnr-strength defines the degree to which noise is filtered (0..6, higher implies stronger filtering)

-- arnr-type defines whether the filter window places the ARF frame as the first, last, or center frame in the filter window (NOTE: this parameter has been deprecated and will be removed from future releases of the API).

Through experimentation we have found that arnr-maxframes=7, arnr-strength=5, arnr-type=3 (the default) works well.

Hope this helps,

Adrian

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