changeset 11908:4ed6afba6047

Disable QP limitations for lowpass subband dct
author hribeiro
date Wed, 08 Nov 2017 10:58:47 +0530
parents 0925ba3c6214
children 6a882a9300c2
files doc/reST/cli.rst source/common/primitives.cpp source/x265.h
diffstat 3 files changed, 9 insertions(+-), 9 deletions(-) [+]
line wrap: on
line diff
--- a/doc/reST/cli.rst	Tue Nov 07 12:43:23 2017 +0530
+++ b/doc/reST/cli.rst	Wed Nov 08 10:58:47 2017 +0530
@@ -2170,15 +2170,16 @@ DCT Approximations
 
 .. option:: --lowpass-dct
 
-    If enabled, x265 will use low-pass truncated dct approximation instead of the
-    standard dct. This approximation is less computational intesive but it generates
-    truncated coefficient matrixes for the transformed block. Empirical analysis shows
-    this approximation gives good PSNR results for QP>=23. 
+    If enabled, x265 will use low-pass subband dct approximation instead of the
+    standard dct for 16x16 and 32x32 blocks. This approximation is less computational 
+    intensive but it generates truncated coefficient matrixes for the transformed block. 
+    Empirical analysis shows marginal loss in compression and performance gains up to 10%,
+    paticularly at moderate bit-rates.
 
     This approximation should be considered for platforms with performance and time 
     constrains.
 
-	Default disabled. **Experimental feature**
+    Default disabled. **Experimental feature**
 
 Debugging options
 =================
--- a/source/common/primitives.cpp	Tue Nov 07 12:43:23 2017 +0530
+++ b/source/common/primitives.cpp	Wed Nov 08 10:58:47 2017 +0530
@@ -272,7 +272,7 @@ void x265_setup_primitives(x265_param *p
 
         setupAliasPrimitives(primitives);
 
-        if (param->bLowPassDct && param->rc.qp > 20)
+        if (param->bLowPassDct)
         {
             enableLowpassDCTPrimitives(primitives); 
         }
--- a/source/x265.h	Tue Nov 07 12:43:23 2017 +0530
+++ b/source/x265.h	Wed Nov 08 10:58:47 2017 +0530
@@ -1515,9 +1515,8 @@ typedef struct x265_param
     /* Disable lookahead */
     int       bDisableLookahead;
 
-    /* Use low-pass truncated dct approximation 
-    *  This DCT approximation is less computational intensive and gives results close to 
-    *  standard DCT for QP >= 23 */
+    /* Use low-pass subband dct approximation 
+    *  This DCT approximation is less computational intensive and gives results close to standard DCT */
     int       bLowPassDct;
 
     /* Sets the portion of the decode buffer that must be available after all the