mirror of https://github.com/mpv-player/mpv
77 lines
3.0 KiB
Plaintext
77 lines
3.0 KiB
Plaintext
HOW TO TEST SNOW
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Snow is an experimental wavelet-based codec made by the FFmpeg developers,
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and while it is still in heavy development, it is already giving very good
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results.
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Be very careful though, as the format of the bitstream produced might
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change, do not rely on it to store videos that you value.
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For this reason, MEncoder will not encode without 'vstrict=-2' on the
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command line.
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OPTIONS RECOGNIZED BY SNOW
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* vqscale=<0.01-255>
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Encoding quality, sane range 1-10, default: 0 (lossless). May be
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fractional.
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A given quality in snow needs a somewhat lower qscale than the same
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quality in MPEG-4.
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Note that 0 may not be specified; if you want lossless encoding, you
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must leave out vqscale.
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* vpass=<1-3>
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Activates internal two (or more) pass mode.
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* vbitrate=<value>
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Specify bitrate of the 2nd pass.
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Don't use it for 1st pass as CBR isn't implemented yet, use vqscale
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instead, and set it to a quantizer near the target average quant
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of the final encode.
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* lmin, lmax, vqcomp, vratetol, vrc_eq, vrc_override
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Generic multipass ratecontrol options, subject to the same suggestions
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as in other codecs.
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lmin=1 can be useful for medium to high bitrates (see vqscale).
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* cmp, subcmp, mbcmp
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Set the comparison function, default: 0 (SAD).
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useful values = 0 (SAD), 1 (SSD), 11 (5/3 wavelet), 12 (9/7 wavelet).
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Experience shows that SSD is the best most of the time, while SAD is
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slightly better the remainder of the time.
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You can add 256 to any of the options to enable chroma motion
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estimation for that comparison (e.g. mbcmp=257 for SSD with chroma),
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but it doesn't seem to help much for the moment.
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* pred=<0-2>
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Wavelet type. 0 (9/7 wavelet), 1 (5/3 wavelet), 2 (13/7 wavelet).
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9/7 is probably better for for lossy coding, and 5/3 for lossless.
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NOTE: 9/7 wavelet doesn't work with lossless mode.
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* qpel
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Refines motion estimation, default: off.
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This setting always helps compressibility, but costs some CPU time
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both while encoding and decoding.
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* v4mv
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Allows smaller motion partitions, default: off.
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The current MB decision algorithm doesn't make very good use of this:
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It improves quality, but also increases bitrate. (You could get
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more quality per bitrate by reducing quantizer instead.)
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* vme=<4|8>
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The default EPZS (4) is the same as in other formats.
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Snow also supports iterative motion estimation (8), which jointly
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optimizes adjacent blocks to make the most of OBMC. This significantly
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improves compression, but is very slow.
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Iterative ME currently does not perform scenecut detection, so should
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be used only in the second pass of a two pass encode.
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v4mv and the wavelet cmp functions are theoretically good, but in practice
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aren't really working yet.
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In short:
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The best options in almost all cases are
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vcodec=snow:vstrict=-2:vpass=1:vqscale=$N:pred=0:cmp=1:subcmp=1:mbcmp=1:qpel
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vcodec=snow:vstrict=-2:vpass=2:vbitrate=$B:pred=0:cmp=1:subcmp=1:mbcmp=1:qpel:vme=8
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