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-rw-r--r--CMakeLists.txt2
-rw-r--r--ChangeLog.txt8
-rw-r--r--Makefile.am6
-rwxr-xr-xREADME-turbo.txt15
-rw-r--r--jidctflt.c83
5 files changed, 61 insertions, 53 deletions
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 8d7c9b7..40e1433 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -300,7 +300,7 @@ set(MD5_JPEG_3x2_FLOAT_PROG 343e3f8caf8af5986ebaf0bdc13b5c71)
set(MD5_PPM_3x2_FLOAT 1a75f36e5904d6fc3a85a43da9ad89bb)
else()
set(MD5_JPEG_3x2_FLOAT_PROG 9bca803d2042bd1eb03819e2bf92b3e5)
-set(MD5_PPM_3x2_FLOAT ef6a420e369440edd6b918a0cf54ba3f)
+set(MD5_PPM_3x2_FLOAT f6bfab038438ed8f5522fbd33595dcdc)
endif()
set(MD5_JPEG_420_ISLOW_ARI e986fb0a637a8d833d96e8a6d6d84ea1)
set(MD5_JPEG_444_ISLOW_PROGARI 0a8f1c8f66e113c3cf635df0a475a617)
diff --git a/ChangeLog.txt b/ChangeLog.txt
index 84842e5..f68a988 100644
--- a/ChangeLog.txt
+++ b/ChangeLog.txt
@@ -54,6 +54,14 @@ if compiler optimization was enabled when libjpeg-turbo was built. This caused
the regression tests to fail when doing a release build under Visual C++ 2010
and later.
+[7] Improved the accuracy and performance of the non-SIMD implementation of the
+floating point inverse DCT (using code borrowed from libjpeg v8a and later.)
+The accuracy of this implementation now matches the accuracy of the SSE/SSE2
+implementation. Note, however, that the floating point DCT/IDCT algorithms are
+mainly a legacy feature. They generally do not produce significantly better
+accuracy than the slow integer DCT/IDCT algorithms, and they are quite a bit
+slower.
+
1.3.1
=====
diff --git a/Makefile.am b/Makefile.am
index f14ddbf..1844672 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -175,15 +175,13 @@ MD5_JPEG_GRAY_ISLOW = 72b51f894b8f4a10b3ee3066770aa38d
MD5_PPM_GRAY_ISLOW = 8d3596c56eace32f205deccc229aa5ed
MD5_PPM_GRAY_RGB_ISLOW = 116424ac07b79e5e801f00508eab48ec
MD5_JPEG_420S_IFAST_OPT = 388708217ac46273ca33086b22827ed8
-# The SSE/SSE2 DCT/IDCT implementation has always produced a slight round-off
-# error relative to the C code, so in this case, we just test for regression
-# rather than verifying that the output matches libjpeg.
+# See README-turbo.txt for more details on why this next bit is necessary.
if WITH_SSE_FLOAT_DCT
MD5_JPEG_3x2_FLOAT_PROG = 343e3f8caf8af5986ebaf0bdc13b5c71
MD5_PPM_3x2_FLOAT = 1a75f36e5904d6fc3a85a43da9ad89bb
else
MD5_JPEG_3x2_FLOAT_PROG = 9bca803d2042bd1eb03819e2bf92b3e5
-MD5_PPM_3x2_FLOAT = ef6a420e369440edd6b918a0cf54ba3f
+MD5_PPM_3x2_FLOAT = f6bfab038438ed8f5522fbd33595dcdc
endif
MD5_JPEG_420_ISLOW_ARI = e986fb0a637a8d833d96e8a6d6d84ea1
MD5_JPEG_444_ISLOW_PROGARI = 0a8f1c8f66e113c3cf635df0a475a617
diff --git a/README-turbo.txt b/README-turbo.txt
index 944e1b9..f5cd613 100755
--- a/README-turbo.txt
+++ b/README-turbo.txt
@@ -301,10 +301,19 @@ following reasons:
slightly more accurate than the implementation in libjpeg v6b, but not by
any amount perceptible to human vision (generally in the range of 0.01 to
0.08 dB gain in PNSR.)
+-- When not using the SIMD extensions, libjpeg-turbo uses the more accurate
+ (and slightly faster) floating point IDCT algorithm introduced in libjpeg
+ v8a as opposed to the algorithm used in libjpeg v6b. It should be noted,
+ however, that this algorithm basically brings the accuracy of the floating
+ point IDCT in line with the accuracy of the slow integer IDCT. The floating
+ point DCT/IDCT algorithms are mainly a legacy feature, and they do not
+ produce significantly more accuracy than the slow integer algorithms (to put
+ numbers on this, the typical difference in PNSR between the two algorithms
+ is less than 0.10 dB, whereas changing the quality level by 1 in the upper
+ range of the quality scale is typically more like a 1.0 dB difference.)
-- When not using the SIMD extensions, then the accuracy of the floating point
DCT/IDCT can depend on the compiler and compiler settings.
-
While libjpeg-turbo does emulate the libjpeg v8 API/ABI, under the hood, it is
still using the same algorithms as libjpeg v6b, so there are several specific
cases in which libjpeg-turbo cannot be expected to produce the same output as
@@ -320,10 +329,6 @@ libjpeg v8:
output of libjpeg v8 is less accurate than that of libjpeg v6b for this
reason.
--- When using the floating point IDCT, for the reasons stated above and also
- because the floating point IDCT algorithm was modified in libjpeg v8a to
- improve accuracy.
-
-- When decompressing using a scaling factor > 1 and merged (AKA "non-fancy" or
"non-smooth") chrominance upsampling, because libjpeg v8 does not support
merged upsampling with scaling factors > 1.
diff --git a/jidctflt.c b/jidctflt.c
index c172ea1..2b2e228 100644
--- a/jidctflt.c
+++ b/jidctflt.c
@@ -1,9 +1,12 @@
/*
* jidctflt.c
*
+ * This file was part of the Independent JPEG Group's software:
* Copyright (C) 1994-1998, Thomas G. Lane.
- * This file is part of the Independent JPEG Group's software.
- * For conditions of distribution and use, see the accompanying README file.
+ * Modified 2010 by Guido Vollbeding.
+ * libjpeg-turbo Modifications:
+ * Copyright (C) 2014, D. R. Commander.
+ * For conditions of distribution and use, see the accompanying README file.
*
* This file contains a floating-point implementation of the
* inverse DCT (Discrete Cosine Transform). In the IJG code, this routine
@@ -76,10 +79,10 @@ jpeg_idct_float (j_decompress_ptr cinfo, jpeg_component_info * compptr,
FLOAT_MULT_TYPE * quantptr;
FAST_FLOAT * wsptr;
JSAMPROW outptr;
- JSAMPLE *range_limit = IDCT_range_limit(cinfo);
+ JSAMPLE *range_limit = cinfo->sample_range_limit;
int ctr;
FAST_FLOAT workspace[DCTSIZE2]; /* buffers data between passes */
- SHIFT_TEMPS
+ #define _0_125 ((FLOAT_MULT_TYPE)0.125)
/* Pass 1: process columns from input, store into work array. */
@@ -101,7 +104,8 @@ jpeg_idct_float (j_decompress_ptr cinfo, jpeg_component_info * compptr,
inptr[DCTSIZE*5] == 0 && inptr[DCTSIZE*6] == 0 &&
inptr[DCTSIZE*7] == 0) {
/* AC terms all zero */
- FAST_FLOAT dcval = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]);
+ FAST_FLOAT dcval = DEQUANTIZE(inptr[DCTSIZE*0],
+ quantptr[DCTSIZE*0] * _0_125);
wsptr[DCTSIZE*0] = dcval;
wsptr[DCTSIZE*1] = dcval;
@@ -120,10 +124,10 @@ jpeg_idct_float (j_decompress_ptr cinfo, jpeg_component_info * compptr,
/* Even part */
- tmp0 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]);
- tmp1 = DEQUANTIZE(inptr[DCTSIZE*2], quantptr[DCTSIZE*2]);
- tmp2 = DEQUANTIZE(inptr[DCTSIZE*4], quantptr[DCTSIZE*4]);
- tmp3 = DEQUANTIZE(inptr[DCTSIZE*6], quantptr[DCTSIZE*6]);
+ tmp0 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0] * _0_125);
+ tmp1 = DEQUANTIZE(inptr[DCTSIZE*2], quantptr[DCTSIZE*2] * _0_125);
+ tmp2 = DEQUANTIZE(inptr[DCTSIZE*4], quantptr[DCTSIZE*4] * _0_125);
+ tmp3 = DEQUANTIZE(inptr[DCTSIZE*6], quantptr[DCTSIZE*6] * _0_125);
tmp10 = tmp0 + tmp2; /* phase 3 */
tmp11 = tmp0 - tmp2;
@@ -138,10 +142,10 @@ jpeg_idct_float (j_decompress_ptr cinfo, jpeg_component_info * compptr,
/* Odd part */
- tmp4 = DEQUANTIZE(inptr[DCTSIZE*1], quantptr[DCTSIZE*1]);
- tmp5 = DEQUANTIZE(inptr[DCTSIZE*3], quantptr[DCTSIZE*3]);
- tmp6 = DEQUANTIZE(inptr[DCTSIZE*5], quantptr[DCTSIZE*5]);
- tmp7 = DEQUANTIZE(inptr[DCTSIZE*7], quantptr[DCTSIZE*7]);
+ tmp4 = DEQUANTIZE(inptr[DCTSIZE*1], quantptr[DCTSIZE*1] * _0_125);
+ tmp5 = DEQUANTIZE(inptr[DCTSIZE*3], quantptr[DCTSIZE*3] * _0_125);
+ tmp6 = DEQUANTIZE(inptr[DCTSIZE*5], quantptr[DCTSIZE*5] * _0_125);
+ tmp7 = DEQUANTIZE(inptr[DCTSIZE*7], quantptr[DCTSIZE*7] * _0_125);
z13 = tmp6 + tmp5; /* phase 6 */
z10 = tmp6 - tmp5;
@@ -152,12 +156,12 @@ jpeg_idct_float (j_decompress_ptr cinfo, jpeg_component_info * compptr,
tmp11 = (z11 - z13) * ((FAST_FLOAT) 1.414213562); /* 2*c4 */
z5 = (z10 + z12) * ((FAST_FLOAT) 1.847759065); /* 2*c2 */
- tmp10 = ((FAST_FLOAT) 1.082392200) * z12 - z5; /* 2*(c2-c6) */
- tmp12 = ((FAST_FLOAT) -2.613125930) * z10 + z5; /* -2*(c2+c6) */
+ tmp10 = z5 - z12 * ((FAST_FLOAT) 1.082392200); /* 2*(c2-c6) */
+ tmp12 = z5 - z10 * ((FAST_FLOAT) 2.613125930); /* 2*(c2+c6) */
tmp6 = tmp12 - tmp7; /* phase 2 */
tmp5 = tmp11 - tmp6;
- tmp4 = tmp10 + tmp5;
+ tmp4 = tmp10 - tmp5;
wsptr[DCTSIZE*0] = tmp0 + tmp7;
wsptr[DCTSIZE*7] = tmp0 - tmp7;
@@ -165,8 +169,8 @@ jpeg_idct_float (j_decompress_ptr cinfo, jpeg_component_info * compptr,
wsptr[DCTSIZE*6] = tmp1 - tmp6;
wsptr[DCTSIZE*2] = tmp2 + tmp5;
wsptr[DCTSIZE*5] = tmp2 - tmp5;
- wsptr[DCTSIZE*4] = tmp3 + tmp4;
- wsptr[DCTSIZE*3] = tmp3 - tmp4;
+ wsptr[DCTSIZE*3] = tmp3 + tmp4;
+ wsptr[DCTSIZE*4] = tmp3 - tmp4;
inptr++; /* advance pointers to next column */
quantptr++;
@@ -174,7 +178,6 @@ jpeg_idct_float (j_decompress_ptr cinfo, jpeg_component_info * compptr,
}
/* Pass 2: process rows from work array, store into output array. */
- /* Note that we must descale the results by a factor of 8 == 2**3. */
wsptr = workspace;
for (ctr = 0; ctr < DCTSIZE; ctr++) {
@@ -187,8 +190,10 @@ jpeg_idct_float (j_decompress_ptr cinfo, jpeg_component_info * compptr,
/* Even part */
- tmp10 = wsptr[0] + wsptr[4];
- tmp11 = wsptr[0] - wsptr[4];
+ /* Apply signed->unsigned and prepare float->int conversion */
+ z5 = wsptr[0] + ((FAST_FLOAT) CENTERJSAMPLE + (FAST_FLOAT) 0.5);
+ tmp10 = z5 + wsptr[4];
+ tmp11 = z5 - wsptr[4];
tmp13 = wsptr[2] + wsptr[6];
tmp12 = (wsptr[2] - wsptr[6]) * ((FAST_FLOAT) 1.414213562) - tmp13;
@@ -209,31 +214,23 @@ jpeg_idct_float (j_decompress_ptr cinfo, jpeg_component_info * compptr,
tmp11 = (z11 - z13) * ((FAST_FLOAT) 1.414213562);
z5 = (z10 + z12) * ((FAST_FLOAT) 1.847759065); /* 2*c2 */
- tmp10 = ((FAST_FLOAT) 1.082392200) * z12 - z5; /* 2*(c2-c6) */
- tmp12 = ((FAST_FLOAT) -2.613125930) * z10 + z5; /* -2*(c2+c6) */
+ tmp10 = z5 - z12 * ((FAST_FLOAT) 1.082392200); /* 2*(c2-c6) */
+ tmp12 = z5 - z10 * ((FAST_FLOAT) 2.613125930); /* 2*(c2+c6) */
tmp6 = tmp12 - tmp7;
tmp5 = tmp11 - tmp6;
- tmp4 = tmp10 + tmp5;
-
- /* Final output stage: scale down by a factor of 8 and range-limit */
-
- outptr[0] = range_limit[(int) DESCALE((INT32) (tmp0 + tmp7), 3)
- & RANGE_MASK];
- outptr[7] = range_limit[(int) DESCALE((INT32) (tmp0 - tmp7), 3)
- & RANGE_MASK];
- outptr[1] = range_limit[(int) DESCALE((INT32) (tmp1 + tmp6), 3)
- & RANGE_MASK];
- outptr[6] = range_limit[(int) DESCALE((INT32) (tmp1 - tmp6), 3)
- & RANGE_MASK];
- outptr[2] = range_limit[(int) DESCALE((INT32) (tmp2 + tmp5), 3)
- & RANGE_MASK];
- outptr[5] = range_limit[(int) DESCALE((INT32) (tmp2 - tmp5), 3)
- & RANGE_MASK];
- outptr[4] = range_limit[(int) DESCALE((INT32) (tmp3 + tmp4), 3)
- & RANGE_MASK];
- outptr[3] = range_limit[(int) DESCALE((INT32) (tmp3 - tmp4), 3)
- & RANGE_MASK];
+ tmp4 = tmp10 - tmp5;
+
+ /* Final output stage: float->int conversion and range-limit */
+
+ outptr[0] = range_limit[((int) (tmp0 + tmp7)) & RANGE_MASK];
+ outptr[7] = range_limit[((int) (tmp0 - tmp7)) & RANGE_MASK];
+ outptr[1] = range_limit[((int) (tmp1 + tmp6)) & RANGE_MASK];
+ outptr[6] = range_limit[((int) (tmp1 - tmp6)) & RANGE_MASK];
+ outptr[2] = range_limit[((int) (tmp2 + tmp5)) & RANGE_MASK];
+ outptr[5] = range_limit[((int) (tmp2 - tmp5)) & RANGE_MASK];
+ outptr[3] = range_limit[((int) (tmp3 + tmp4)) & RANGE_MASK];
+ outptr[4] = range_limit[((int) (tmp3 - tmp4)) & RANGE_MASK];
wsptr += DCTSIZE; /* advance pointer to next row */
}
generated by cgit v1.2.3 (git 2.25.1) at 2024-07-20 23:36:34 +0000