document the recent changes in Snow.

new lavcopts: 'refs', 'vqscale=0'



git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@18570 b3059339-0415-0410-9bf9-f77b7e298cf2

2 files changed, 36 insertions, 17 deletions

diff --git a/DOCS/man/en/mplayer.1 b/DOCS/man/en/mplayer.1
index 6e5f6069fa..ceff91994a 100644
--- a/DOCS/man/en/mplayer.1
+++ b/DOCS/man/en/mplayer.1
@@ -7925,6 +7925,11 @@ subpel refinement quality (for qpel) (default: 8 (high quality))
 This has a significant effect on speed.
 .
 .TP
+.B refs=<1\-8>
+number of reference frames to consider for motion compensation
+(Snow only) (default: 1)
+.
+.TP
 .B psnr\ \ \ 
 print the PSNR (peak signal to noise ratio) for the whole video after encoding
 and store the per frame PSNR in a file with a name like 'psnr_hhmmss.log'.
diff --git a/DOCS/tech/snow.txt b/DOCS/tech/snow.txt
index 83823b5211..bcf41e4e39 100644
--- a/DOCS/tech/snow.txt
+++ b/DOCS/tech/snow.txt
@@ -12,22 +12,18 @@ command line.
 
 OPTIONS RECOGNIZED BY SNOW
 
- * vqscale=<0.01-255>
-   Encoding quality, sane range 1-10, default: 0 (lossless). May be
-   fractional.
+ * vqscale=<0.0-255.0>
+   Encoding quality, sane range 1-10. 0 is 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.
+   Specify bitrate of 1pass CBR or 2pass ABR. default: 800 kbit/s.
+   This is not very accurate for short videos.
 
  * lmin, lmax, vqcomp, vratetol, vrc_eq, vrc_override
    Generic multipass ratecontrol options, subject to the same suggestions
@@ -36,15 +32,24 @@ OPTIONS RECOGNIZED BY SNOW
 
  * 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.
+   useful values = 0 (SAD), 1 (SSD), 2 (SATD), 
+                   11 (5/3 wavelet), 12 (9/7 wavelet).
+   SAD is fastest and lowest quality.
+   SSD is the only function that makes correct decisions about intra vs
+   inter (mbcmp) when using fast motion estimation, but is not the best for
+   the actual search (cmp, subcmp).
+   The wavelet functions (use the one that matches pred) are best quality,
+   especially whith vme=8, but are very slow.
+   SATD is a good balance.
    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).
+   Wavelet type.
+   0 = 9/7 wavelet, default.
+   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.
 
@@ -55,6 +60,7 @@ OPTIONS RECOGNIZED BY SNOW
 
  * v4mv
    Allows smaller motion partitions, default: off.
+   v4mv is theoretically good, but in practice isn't really working yet.
    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.)
@@ -67,10 +73,18 @@ OPTIONS RECOGNIZED BY SNOW
    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.
+ * refs=<1-8>
+   Allows each block to choose which of several reference frames to
+   motion compensate from. Defult: 1. Larger values always improve
+   compression, but cost lots of CPU-time when encoding and extra
+   memory when decoding.
 
 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
+vcodec=snow:vstrict=-2:vpass=1:vbitrate=$B:pred=0:cmp=2:subcmp=2:mbcmp=1:qpel
+vcodec=snow:vstrict=-2:vpass=2:vbitrate=$B:pred=0:cmp=12:subcmp=12:mbcmp=1:qpel:vme=8:refs=8
+
+Decent, fast options are
+vcodec=snow:vstrict=-2:vpass=1:vbitrate=$B:pred=0:cmp=1:subcmp=1:mbcmp=1
+vcodec=snow:vstrict=-2:vpass=2:vbitrate=$B:pred=0:cmp=2:subcmp=2:mbcmp=1:refs=2
+