fixing lossless snow

Originally committed as revision 4107 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/snow.c

@@ -3434,7 +3434,7 @@ redo_frame:
         if(s->qlog == LOSSLESS_QLOG){
             for(y=0; y<h; y++){
                 for(x=0; x<w; x++){
-                    s->spatial_dwt_buffer[y*w + x]= (s->spatial_dwt_buffer[y*w + x] + (1<<(FRAC_BITS-1)))>>FRAC_BITS;
+                    s->spatial_dwt_buffer[y*w + x]= (s->spatial_dwt_buffer[y*w + x] + (1<<(FRAC_BITS-1))-1)>>FRAC_BITS;
                 }
             }
         }

tests/ffmpeg.regression.ref

@@ -123,10 +123,10 @@ ba3d08fe9c54acb58cb72e02476849d7 *./data/a-snow.avi
 1280600 ./data/a-snow.avi
 e4b8c83278efee032a84569c25593937 *./data/out.yuv
 stddev:  2.92 PSNR:38.79 bytes:7602176
-bf75e55f91bbc67c3efeaa023aae99d0 *./data/a-snow53.avi
-3555724 ./data/a-snow53.avi
-b8c0eea1938575abf0ae8bfb0bec7b92 *./data/out.yuv
-stddev:  0.14 PSNR:64.73 bytes:7602176
+7acf773e701b92dbc15a6852aac329b6 *./data/a-snow53.avi
+3537412 ./data/a-snow53.avi
+799d3db687f6cdd7a837ec156efc171f *./data/out.yuv
+stddev:  0.00 PSNR:99.99 bytes:7602176
 b5b6275f58f012de73644bbaa9080097 *./data/a-svq1.mov
 1383999 ./data/a-svq1.mov
 ccc201054669e94717022bb4f2aea4ce *./data/out.yuv

tests/rotozoom.regression.ref

@@ -123,10 +123,10 @@ stddev:  0.00 PSNR:99.99 bytes:7602176
 332700 ./data/a-snow.avi
 1f3439e1b3ff09492f196a024d7119e3 *./data/out.yuv
 stddev:  2.37 PSNR:40.60 bytes:7602176
-d20607f4f75a7638e6c73e701c4b1fd3 *./data/a-snow53.avi
-2727012 ./data/a-snow53.avi
-b0d84bc6d6722d9ff5c9680358b97ab3 *./data/out.yuv
-stddev:  0.10 PSNR:67.58 bytes:7602176
+eaea93acf339ad2a7349dc5d0872e870 *./data/a-snow53.avi
+2724574 ./data/a-snow53.avi
+dde5895817ad9d219f79a52d0bdfb001 *./data/out.yuv
+stddev:  0.00 PSNR:99.99 bytes:7602176
 920c610ec324b772d882b0717e375943 *./data/a-svq1.mov
 768683 ./data/a-svq1.mov
 89b1946242e6998e05fc9a6e09668edd *./data/out.yuv