[FFmpeg-devel] [PATCH] libswscale/swscale_unscaled: fix DITHER_COPY macro
Mateusz
mateuszb at poczta.onet.pl
Wed Sep 6 10:27:23 EEST 2017
W dniu 2017-09-06 o 02:07, Michael Niedermayer pisze:
> On Wed, Sep 06, 2017 at 01:25:45AM +0200, Mateusz wrote:
>> W dniu 2017-09-05 o 23:37, Michael Niedermayer pisze:
>>> On Tue, Sep 05, 2017 at 04:42:06PM +0200, Mateusz wrote:
>>>> W dniu 2017-09-05 o 15:40, Michael Niedermayer pisze:
>>>>> On Mon, Sep 04, 2017 at 09:33:34AM +0200, Mateusz wrote:
>>>>>> If ffmpeg reduces bit-depth to 8-bit or more, it uses DITHER_COPY macro.
>>>>>> The problem is DITHER_COPY macro make images darker (on all planes).
>>>>>>
>>>>>> In x265 project there is issue #365 which is caused by this DITHER_COPY bug.
>>>>>> I think it is time to fix -- there are more and more high bit-depth sources.
>>>>>>
>>>>>> Please review.
>>>>>>
>>>>>> libswscale/swscale_unscaled.c | 44 +++++++++++++------------------------------
>>>>>> 1 file changed, 13 insertions(+), 31 deletions(-)
>>>>>
>>>>> please provide a git compatible patch with with commit message as produced
>>>>> by git format-patch or git send-email
>>>>>
>>>>> this mail is not accepted as is by git
>>>>> Applying: libswscale/swscale_unscaled: fix DITHER_COPY macro
>>>>> error: corrupt patch at line 6
>>>>> error: could not build fake ancestor
>>>>> Patch failed at 0001 libswscale/swscale_unscaled: fix DITHER_COPY macro
>>>>>
>>>>> [...]
>>>>
>>>> I've attached the result of git format-patch command.
>>>>
>>>> Sorry for 1 private e-mail (I clicked wrong button).
>>>>
>>>> Mateusz
>>>
>>>> swscale_unscaled.c | 44 +++++++++++++-------------------------------
>>>> 1 file changed, 13 insertions(+), 31 deletions(-)
>>>> 9973b13b3f74319abe9c97302ee87b2b3468b3b6 0001-fix-DITHER_COPY-macro-to-avoid-make-images-darker.patch
>>>> From 9b96d612fef46ccec7e148cd7f8e8666b4e7a4cd Mon Sep 17 00:00:00 2001
>>>> From: Mateusz <mateuszb at poczta.onet.pl>
>>>> Date: Tue, 5 Sep 2017 16:09:28 +0200
>>>> Subject: [PATCH] fix DITHER_COPY macro to avoid make images darker
>>>>
>>>> ---
>>>> libswscale/swscale_unscaled.c | 44 +++++++++++++------------------------------
>>>> 1 file changed, 13 insertions(+), 31 deletions(-)
>>>>
>>>> diff --git a/libswscale/swscale_unscaled.c b/libswscale/swscale_unscaled.c
>>>> index ef36aec..3b7a5a9 100644
>>>> --- a/libswscale/swscale_unscaled.c
>>>> +++ b/libswscale/swscale_unscaled.c
>>>> @@ -110,24 +110,6 @@ DECLARE_ALIGNED(8, static const uint8_t, dithers)[8][8][8]={
>>>> { 112, 16,104, 8,118, 22,110, 14,},
>>>> }};
>>>>
>>>> -static const uint16_t dither_scale[15][16]={
>>>> -{ 2, 3, 3, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,},
>>>> -{ 2, 3, 7, 7, 13, 13, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,},
>>>> -{ 3, 3, 4, 15, 15, 29, 57, 57, 57, 113, 113, 113, 113, 113, 113, 113,},
>>>> -{ 3, 4, 4, 5, 31, 31, 61, 121, 241, 241, 241, 241, 481, 481, 481, 481,},
>>>> -{ 3, 4, 5, 5, 6, 63, 63, 125, 249, 497, 993, 993, 993, 993, 993, 1985,},
>>>> -{ 3, 5, 6, 6, 6, 7, 127, 127, 253, 505, 1009, 2017, 4033, 4033, 4033, 4033,},
>>>> -{ 3, 5, 6, 7, 7, 7, 8, 255, 255, 509, 1017, 2033, 4065, 8129,16257,16257,},
>>>> -{ 3, 5, 6, 8, 8, 8, 8, 9, 511, 511, 1021, 2041, 4081, 8161,16321,32641,},
>>>> -{ 3, 5, 7, 8, 9, 9, 9, 9, 10, 1023, 1023, 2045, 4089, 8177,16353,32705,},
>>>> -{ 3, 5, 7, 8, 10, 10, 10, 10, 10, 11, 2047, 2047, 4093, 8185,16369,32737,},
>>>> -{ 3, 5, 7, 8, 10, 11, 11, 11, 11, 11, 12, 4095, 4095, 8189,16377,32753,},
>>>> -{ 3, 5, 7, 9, 10, 12, 12, 12, 12, 12, 12, 13, 8191, 8191,16381,32761,},
>>>> -{ 3, 5, 7, 9, 10, 12, 13, 13, 13, 13, 13, 13, 14,16383,16383,32765,},
>>>> -{ 3, 5, 7, 9, 10, 12, 14, 14, 14, 14, 14, 14, 14, 15,32767,32767,},
>>>> -{ 3, 5, 7, 9, 11, 12, 14, 15, 15, 15, 15, 15, 15, 15, 16,65535,},
>>>> -};
>>>> -
>>>>
>>>> static void fillPlane(uint8_t *plane, int stride, int width, int height, int y,
>>>> uint8_t val)
>>>> @@ -1502,22 +1484,22 @@ static int packedCopyWrapper(SwsContext *c, const uint8_t *src[],
>>>> }
>>>>
>>>> #define DITHER_COPY(dst, dstStride, src, srcStride, bswap, dbswap)\
>>>> - uint16_t scale= dither_scale[dst_depth-1][src_depth-1];\
>>>> - int shift= src_depth-dst_depth + dither_scale[src_depth-2][dst_depth-1];\
>>>> + unsigned shift= src_depth-dst_depth, tmp;\
>>>> for (i = 0; i < height; i++) {\
>>>> - const uint8_t *dither= dithers[src_depth-9][i&7];\
>>>> + const uint8_t *dither= dithers[shift-1][i&7];\
>>>> for (j = 0; j < length-7; j+=8){\
>>>> - dst[j+0] = dbswap((bswap(src[j+0]) + dither[0])*scale>>shift);\
>>>> - dst[j+1] = dbswap((bswap(src[j+1]) + dither[1])*scale>>shift);\
>>>> - dst[j+2] = dbswap((bswap(src[j+2]) + dither[2])*scale>>shift);\
>>>> - dst[j+3] = dbswap((bswap(src[j+3]) + dither[3])*scale>>shift);\
>>>> - dst[j+4] = dbswap((bswap(src[j+4]) + dither[4])*scale>>shift);\
>>>> - dst[j+5] = dbswap((bswap(src[j+5]) + dither[5])*scale>>shift);\
>>>> - dst[j+6] = dbswap((bswap(src[j+6]) + dither[6])*scale>>shift);\
>>>> - dst[j+7] = dbswap((bswap(src[j+7]) + dither[7])*scale>>shift);\
>>>> + tmp = (bswap(src[j+0]) + dither[0])>>shift; dst[j+0] = dbswap(tmp - (tmp>>dst_depth));\
>>>> + tmp = (bswap(src[j+1]) + dither[1])>>shift; dst[j+1] = dbswap(tmp - (tmp>>dst_depth));\
>>>> + tmp = (bswap(src[j+2]) + dither[2])>>shift; dst[j+2] = dbswap(tmp - (tmp>>dst_depth));\
>>>> + tmp = (bswap(src[j+3]) + dither[3])>>shift; dst[j+3] = dbswap(tmp - (tmp>>dst_depth));\
>>>> + tmp = (bswap(src[j+4]) + dither[4])>>shift; dst[j+4] = dbswap(tmp - (tmp>>dst_depth));\
>>>> + tmp = (bswap(src[j+5]) + dither[5])>>shift; dst[j+5] = dbswap(tmp - (tmp>>dst_depth));\
>>>> + tmp = (bswap(src[j+6]) + dither[6])>>shift; dst[j+6] = dbswap(tmp - (tmp>>dst_depth));\
>>>> + tmp = (bswap(src[j+7]) + dither[7])>>shift; dst[j+7] = dbswap(tmp - (tmp>>dst_depth));\
>>>
>>> This does not look correct
>>>
>>> flat black should be mapped to flat black (ok)
>>> flat white should be mapped to flat white (ok)
>>> black+1 should not be mapped to flat black but to a dithered pattern mixing black with the next brighter color (ok)
>>> white-1 should not be mapped to flat white but to a dithered pattern mixing white with the next darker color (not ok)
>>>
>>> example if you take 9 bit to 7 bit
>>> 511 + {0..3} = {511..514}
>>> {511..514} >> 2 = {127,128}
>>> {127,128} - ({127,128} >> 7) = 127
>>>
>>> 510 + {0..3} = {510..513}
>>> {510..513} >> 2 = {127,128}
>>> {127,128} - ({127,128} >> 7) = 127
>>>
>>> Thus multiple of the brigher colors all get mapped to the same output,
>>> that way the brightest shades become indistingishable and this is not
>>> correct.
>>>
>>> above is based on code review not testing so i might have missed
>>> something
>>>
>>> [...]
>>
>> Yes, you are right.
>>
>> There is one more rule, that is important and (partially) in contradiction to white-1 to not flat white rule:
>
>> if you convert 7-bit source to 9-bit and next resulting 9-bit to 7-bit, it should be the same picture as original.
>
> this would be desirable
>
>
>> if we convert 7 bit white (or max value at plane) == 127, we have 127 << 2 == 508
>> now 508 goes always to 127
>
> This would only be the case if 508 was the white point and not 511
> otherwise
> If you convert 7bit to 9bit, 127 is converted to 511, this would be a
> requirement to maintain white.
> if you use fewer bits it becomes more obvious
> 2 bits to 4 bits
> 3 -> 15 not 3 -> 12
>
> whereever the white and black points are in the input and output
> colorspace they must get converted correctly.
>
>
> [...]
line #1538 in file libswscale/swscale_unscaled.c
int shiftonly = plane == 1 || plane == 2 || (!c->srcRange && plane == 0);
line #421 in file libswscale/swscale_internal.h
int srcRange; ///< 0 = MPG YUV range, 1 = JPG YUV range (source image).
For movies (without special options) ffmpeg always upscale bit-depth by simple shift (127 to 508).
Only for plane 0 and srcRange == 1 (full range) ffmpeg upscale 127 to 511.
For me it is impossible to make DITHER_COPY macro that works OK for both cases, so I attached new version that check shiftonly state and works optimal according to the shiftonly state.
Now in both cases it is original picture after upscale bit-depth -> downscale bit-depth sequence.
Please review.
Mateusz
-------------- next part --------------
From fd9e271ea531d25bc5a708d0dfeb1be5415b90d0 Mon Sep 17 00:00:00 2001
From: Mateusz <mateuszb at poczta.onet.pl>
Date: Wed, 6 Sep 2017 09:05:02 +0200
Subject: [PATCH] fix DITHER_COPY macro according to shiftonly state
---
libswscale/swscale_unscaled.c | 73 ++++++++++++++++++++++---------------------
1 file changed, 38 insertions(+), 35 deletions(-)
diff --git a/libswscale/swscale_unscaled.c b/libswscale/swscale_unscaled.c
index ef36aec..e3e375a 100644
--- a/libswscale/swscale_unscaled.c
+++ b/libswscale/swscale_unscaled.c
@@ -110,24 +110,6 @@ DECLARE_ALIGNED(8, static const uint8_t, dithers)[8][8][8]={
{ 112, 16,104, 8,118, 22,110, 14,},
}};
-static const uint16_t dither_scale[15][16]={
-{ 2, 3, 3, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,},
-{ 2, 3, 7, 7, 13, 13, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,},
-{ 3, 3, 4, 15, 15, 29, 57, 57, 57, 113, 113, 113, 113, 113, 113, 113,},
-{ 3, 4, 4, 5, 31, 31, 61, 121, 241, 241, 241, 241, 481, 481, 481, 481,},
-{ 3, 4, 5, 5, 6, 63, 63, 125, 249, 497, 993, 993, 993, 993, 993, 1985,},
-{ 3, 5, 6, 6, 6, 7, 127, 127, 253, 505, 1009, 2017, 4033, 4033, 4033, 4033,},
-{ 3, 5, 6, 7, 7, 7, 8, 255, 255, 509, 1017, 2033, 4065, 8129,16257,16257,},
-{ 3, 5, 6, 8, 8, 8, 8, 9, 511, 511, 1021, 2041, 4081, 8161,16321,32641,},
-{ 3, 5, 7, 8, 9, 9, 9, 9, 10, 1023, 1023, 2045, 4089, 8177,16353,32705,},
-{ 3, 5, 7, 8, 10, 10, 10, 10, 10, 11, 2047, 2047, 4093, 8185,16369,32737,},
-{ 3, 5, 7, 8, 10, 11, 11, 11, 11, 11, 12, 4095, 4095, 8189,16377,32753,},
-{ 3, 5, 7, 9, 10, 12, 12, 12, 12, 12, 12, 13, 8191, 8191,16381,32761,},
-{ 3, 5, 7, 9, 10, 12, 13, 13, 13, 13, 13, 13, 14,16383,16383,32765,},
-{ 3, 5, 7, 9, 10, 12, 14, 14, 14, 14, 14, 14, 14, 15,32767,32767,},
-{ 3, 5, 7, 9, 11, 12, 14, 15, 15, 15, 15, 15, 15, 15, 16,65535,},
-};
-
static void fillPlane(uint8_t *plane, int stride, int width, int height, int y,
uint8_t val)
@@ -1502,24 +1484,45 @@ static int packedCopyWrapper(SwsContext *c, const uint8_t *src[],
}
#define DITHER_COPY(dst, dstStride, src, srcStride, bswap, dbswap)\
- uint16_t scale= dither_scale[dst_depth-1][src_depth-1];\
- int shift= src_depth-dst_depth + dither_scale[src_depth-2][dst_depth-1];\
- for (i = 0; i < height; i++) {\
- const uint8_t *dither= dithers[src_depth-9][i&7];\
- for (j = 0; j < length-7; j+=8){\
- dst[j+0] = dbswap((bswap(src[j+0]) + dither[0])*scale>>shift);\
- dst[j+1] = dbswap((bswap(src[j+1]) + dither[1])*scale>>shift);\
- dst[j+2] = dbswap((bswap(src[j+2]) + dither[2])*scale>>shift);\
- dst[j+3] = dbswap((bswap(src[j+3]) + dither[3])*scale>>shift);\
- dst[j+4] = dbswap((bswap(src[j+4]) + dither[4])*scale>>shift);\
- dst[j+5] = dbswap((bswap(src[j+5]) + dither[5])*scale>>shift);\
- dst[j+6] = dbswap((bswap(src[j+6]) + dither[6])*scale>>shift);\
- dst[j+7] = dbswap((bswap(src[j+7]) + dither[7])*scale>>shift);\
+ unsigned shift= src_depth-dst_depth, tmp;\
+ if (shiftonly) {\
+ for (i = 0; i < height; i++) {\
+ const uint8_t *dither= dithers[shift-1][i&7];\
+ for (j = 0; j < length-7; j+=8){\
+ tmp = (bswap(src[j+0]) + dither[0])>>shift; dst[j+0] = dbswap(tmp - (tmp>>dst_depth));\
+ tmp = (bswap(src[j+1]) + dither[1])>>shift; dst[j+1] = dbswap(tmp - (tmp>>dst_depth));\
+ tmp = (bswap(src[j+2]) + dither[2])>>shift; dst[j+2] = dbswap(tmp - (tmp>>dst_depth));\
+ tmp = (bswap(src[j+3]) + dither[3])>>shift; dst[j+3] = dbswap(tmp - (tmp>>dst_depth));\
+ tmp = (bswap(src[j+4]) + dither[4])>>shift; dst[j+4] = dbswap(tmp - (tmp>>dst_depth));\
+ tmp = (bswap(src[j+5]) + dither[5])>>shift; dst[j+5] = dbswap(tmp - (tmp>>dst_depth));\
+ tmp = (bswap(src[j+6]) + dither[6])>>shift; dst[j+6] = dbswap(tmp - (tmp>>dst_depth));\
+ tmp = (bswap(src[j+7]) + dither[7])>>shift; dst[j+7] = dbswap(tmp - (tmp>>dst_depth));\
+ }\
+ for (; j < length; j++){\
+ tmp = (bswap(src[j]) + dither[j&7])>>shift; dst[j] = dbswap(tmp - (tmp>>dst_depth));\
+ }\
+ dst += dstStride;\
+ src += srcStride;\
+ }\
+ } else {\
+ for (i = 0; i < height; i++) {\
+ const uint8_t *dither= dithers[shift-1][i&7];\
+ for (j = 0; j < length-7; j+=8){\
+ tmp = bswap(src[j+0]); dst[j+0] = dbswap((tmp - (tmp>>dst_depth) + dither[0])>>shift);\
+ tmp = bswap(src[j+1]); dst[j+1] = dbswap((tmp - (tmp>>dst_depth) + dither[1])>>shift);\
+ tmp = bswap(src[j+2]); dst[j+2] = dbswap((tmp - (tmp>>dst_depth) + dither[2])>>shift);\
+ tmp = bswap(src[j+3]); dst[j+3] = dbswap((tmp - (tmp>>dst_depth) + dither[3])>>shift);\
+ tmp = bswap(src[j+4]); dst[j+4] = dbswap((tmp - (tmp>>dst_depth) + dither[4])>>shift);\
+ tmp = bswap(src[j+5]); dst[j+5] = dbswap((tmp - (tmp>>dst_depth) + dither[5])>>shift);\
+ tmp = bswap(src[j+6]); dst[j+6] = dbswap((tmp - (tmp>>dst_depth) + dither[6])>>shift);\
+ tmp = bswap(src[j+7]); dst[j+7] = dbswap((tmp - (tmp>>dst_depth) + dither[7])>>shift);\
+ }\
+ for (; j < length; j++){\
+ tmp = bswap(src[j]); dst[j] = dbswap((tmp - (tmp>>dst_depth) + dither[j&7])>>shift);\
+ }\
+ dst += dstStride;\
+ src += srcStride;\
}\
- for (; j < length; j++)\
- dst[j] = dbswap((bswap(src[j]) + dither[j&7])*scale>>shift);\
- dst += dstStride;\
- src += srcStride;\
}
static int planarCopyWrapper(SwsContext *c, const uint8_t *src[],
--
2.7.4
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