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