FFmpeg
vf_cas.c
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1 /*
2  * This file is part of FFmpeg.
3  *
4  * FFmpeg is free software; you can redistribute it and/or
5  * modify it under the terms of the GNU Lesser General Public
6  * License as published by the Free Software Foundation; either
7  * version 2.1 of the License, or (at your option) any later version.
8  *
9  * FFmpeg is distributed in the hope that it will be useful,
10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12  * Lesser General Public License for more details.
13  *
14  * You should have received a copy of the GNU Lesser General Public
15  * License along with FFmpeg; if not, write to the Free Software
16  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
17  */
18 
19 #include "libavutil/opt.h"
20 #include "libavutil/imgutils.h"
21 #include "avfilter.h"
22 #include "formats.h"
23 #include "internal.h"
24 #include "video.h"
25 
26 typedef struct CASContext {
27  const AVClass *class;
28 
29  float strength;
30  int planes;
31  int nb_planes;
32 
33  int depth;
34  int planeheight[4];
35  int planewidth[4];
36 
38 
40  int jobnr, int nb_jobs);
41 } CASContext;
42 
43 static inline float lerpf(float v0, float v1, float f)
44 {
45  return v0 + (v1 - v0) * f;
46 }
47 
48 static int cas_slice8(AVFilterContext *avctx, void *arg, int jobnr, int nb_jobs)
49 {
50  CASContext *s = avctx->priv;
51  const float strength = -lerpf(16.f, 4.01f, s->strength);
52  AVFrame *out = arg;
53  AVFrame *in = s->in;
54 
55  for (int p = 0; p < s->nb_planes; p++) {
56  const int slice_start = (s->planeheight[p] * jobnr) / nb_jobs;
57  const int slice_end = (s->planeheight[p] * (jobnr+1)) / nb_jobs;
58  const int linesize = out->linesize[p];
59  const int in_linesize = in->linesize[p];
60  const int w = s->planewidth[p];
61  const int w1 = w - 1;
62  const int h = s->planeheight[p];
63  const int h1 = h - 1;
64  uint8_t *dst = out->data[p] + slice_start * linesize;
65  const uint8_t *src = in->data[p];
66 
67  if (!((1 << p) & s->planes)) {
68  av_image_copy_plane(dst, linesize, src + slice_start * linesize, in_linesize,
69  w, slice_end - slice_start);
70  continue;
71  }
72 
73  for (int y = slice_start; y < slice_end; y++) {
74  const int y0 = FFMAX(y - 1, 0);
75  const int y1 = FFMIN(y + 1, h1);
76  for (int x = 0; x < w; x++) {
77  const int x0 = FFMAX(x - 1, 0);
78  const int x1 = FFMIN(x + 1, w1);
79  int a = src[y0 * in_linesize + x0];
80  int b = src[y0 * in_linesize + x];
81  int c = src[y0 * in_linesize + x1];
82  int d = src[y * in_linesize + x0];
83  int e = src[y * in_linesize + x];
84  int f = src[y * in_linesize + x1];
85  int g = src[y1 * in_linesize + x0];
86  int h = src[y1 * in_linesize + x];
87  int i = src[y1 * in_linesize + x1];
88  int mn, mn2, mx, mx2;
89  float amp, weight;
90 
91  mn = FFMIN3(FFMIN3( d, e, f), b, h);
92  mn2 = FFMIN3(FFMIN3(mn, a, c), g, i);
93 
94  mn = mn + mn2;
95 
96  mx = FFMAX3(FFMAX3( d, e, f), b, h);
97  mx2 = FFMAX3(FFMAX3(mx, a, c), g, i);
98 
99  mx = mx + mx2;
100 
101  amp = sqrtf(av_clipf(FFMIN(mn, 511 - mx) / (float)mx, 0.f, 1.f));
102 
103  weight = amp / strength;
104 
105  dst[x] = av_clip_uint8(((b + d + f + h) * weight + e) / (1.f + 4.f * weight));
106  }
107  dst += linesize;
108  }
109  }
110 
111  return 0;
112 }
113 
114 static int cas_slice16(AVFilterContext *avctx, void *arg, int jobnr, int nb_jobs)
115 {
116  CASContext *s = avctx->priv;
117  const float strength = -lerpf(16.f, 4.01f, s->strength);
118  const int max = 2 * (1 << s->depth) - 1;
119  AVFrame *out = arg;
120  AVFrame *in = s->in;
121 
122  for (int p = 0; p < s->nb_planes; p++) {
123  const int slice_start = (s->planeheight[p] * jobnr) / nb_jobs;
124  const int slice_end = (s->planeheight[p] * (jobnr+1)) / nb_jobs;
125  const int linesize = out->linesize[p] / 2;
126  const int in_linesize = in->linesize[p] / 2;
127  const int w = s->planewidth[p];
128  const int w1 = w - 1;
129  const int h = s->planeheight[p];
130  const int h1 = h - 1;
131  uint16_t *dst = (uint16_t *)out->data[p] + slice_start * linesize;
132  const uint16_t *src = (const uint16_t *)in->data[p];
133 
134  if (!((1 << p) & s->planes)) {
135  av_image_copy_plane((uint8_t *)dst, linesize, (uint8_t *)(src + slice_start * linesize),
136  in_linesize, w * 2, slice_end - slice_start);
137  continue;
138  }
139 
140  for (int y = slice_start; y < slice_end; y++) {
141  const int y0 = FFMAX(y - 1, 0);
142  const int y1 = FFMIN(y + 1, h1);
143  for (int x = 0; x < w; x++) {
144  const int x0 = FFMAX(x - 1, 0);
145  const int x1 = FFMIN(x + 1, w1);
146  int a = src[y0 * in_linesize + x0];
147  int b = src[y0 * in_linesize + x];
148  int c = src[y0 * in_linesize + x1];
149  int d = src[y * in_linesize + x0];
150  int e = src[y * in_linesize + x];
151  int f = src[y * in_linesize + x1];
152  int g = src[y1 * in_linesize + x0];
153  int h = src[y1 * in_linesize + x];
154  int i = src[y1 * in_linesize + x1];
155  int mn, mn2, mx, mx2;
156  float amp, weight;
157 
158  mn = FFMIN3(FFMIN3( d, e, f), b, h);
159  mn2 = FFMIN3(FFMIN3(mn, a, c), g, i);
160 
161  mn = mn + mn2;
162 
163  mx = FFMAX3(FFMAX3( d, e, f), b, h);
164  mx2 = FFMAX3(FFMAX3(mx, a, c), g, i);
165 
166  mx = mx + mx2;
167 
168  amp = sqrtf(av_clipf(FFMIN(mn, max - mx) / (float)mx, 0.f, 1.f));
169 
170  weight = amp / strength;
171 
172  dst[x] = av_clip_uintp2_c(((b + d + f + h) * weight + e) / (1.f + 4.f * weight), s->depth);
173  }
174  dst += linesize;
175  }
176  }
177 
178  return 0;
179 }
180 
182 {
183  AVFilterContext *ctx = inlink->dst;
184  AVFilterLink *outlink = ctx->outputs[0];
185  CASContext *s = ctx->priv;
186  AVFrame *out;
187 
188  out = ff_get_video_buffer(outlink, outlink->w, outlink->h);
189  if (!out) {
190  av_frame_free(&in);
191  return AVERROR(ENOMEM);
192  }
193  av_frame_copy_props(out, in);
194 
195  s->in = in;
196  ctx->internal->execute(ctx, s->do_slice, out, NULL,
198  av_frame_free(&in);
199  s->in = NULL;
200 
201  return ff_filter_frame(ctx->outputs[0], out);
202 }
203 
205 {
206  static const enum AVPixelFormat pixel_fmts[] = {
231  };
232 
234 
235  formats = ff_make_format_list(pixel_fmts);
236  if (!formats)
237  return AVERROR(ENOMEM);
238 
239  return ff_set_common_formats(avctx, formats);
240 }
241 
243 {
244  AVFilterContext *avctx = inlink->dst;
245  CASContext *s = avctx->priv;
247 
248  s->planeheight[1] = s->planeheight[2] = AV_CEIL_RSHIFT(inlink->h, desc->log2_chroma_h);
249  s->planeheight[0] = s->planeheight[3] = inlink->h;
250  s->planewidth[1] = s->planewidth[2] = AV_CEIL_RSHIFT(inlink->w, desc->log2_chroma_w);
251  s->planewidth[0] = s->planewidth[3] = inlink->w;
252 
253  s->depth = desc->comp[0].depth;
254  s->nb_planes = desc->nb_components;
255  s->do_slice = s->depth <= 8 ? cas_slice8 : cas_slice16;
256 
257  return 0;
258 }
259 
260 static const AVFilterPad cas_inputs[] = {
261  {
262  .name = "default",
263  .type = AVMEDIA_TYPE_VIDEO,
264  .filter_frame = filter_frame,
265  .config_props = config_input,
266  },
267  { NULL }
268 };
269 
270 static const AVFilterPad cas_outputs[] = {
271  {
272  .name = "default",
273  .type = AVMEDIA_TYPE_VIDEO,
274  },
275  { NULL }
276 };
277 
278 #define OFFSET(x) offsetof(CASContext, x)
279 #define VF AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM|AV_OPT_FLAG_RUNTIME_PARAM
280 
281 static const AVOption cas_options[] = {
282  { "strength", "set the sharpening strength", OFFSET(strength), AV_OPT_TYPE_FLOAT, {.dbl=0}, 0, 1, VF },
283  { "planes", "set what planes to filter", OFFSET(planes), AV_OPT_TYPE_FLAGS, {.i64=7}, 0, 15, VF },
284  { NULL }
285 };
286 
288 
290  .name = "cas",
291  .description = NULL_IF_CONFIG_SMALL("Contrast Adaptive Sharpen."),
292  .priv_size = sizeof(CASContext),
293  .priv_class = &cas_class,
295  .inputs = cas_inputs,
296  .outputs = cas_outputs,
299 };
#define NULL
Definition: coverity.c:32
AVFILTER_DEFINE_CLASS(cas)
#define AV_PIX_FMT_YUVA422P16
Definition: pixfmt.h:442
#define VF
Definition: vf_cas.c:279
#define AV_PIX_FMT_YUV440P10
Definition: pixfmt.h:401
#define AV_PIX_FMT_YUVA422P9
Definition: pixfmt.h:434
const AVPixFmtDescriptor * av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
Definition: pixdesc.c:2573
This structure describes decoded (raw) audio or video data.
Definition: frame.h:308
AVOption.
Definition: opt.h:248
#define AV_PIX_FMT_YUVA420P10
Definition: pixfmt.h:436
#define AV_PIX_FMT_YUV444P14
Definition: pixfmt.h:409
#define AV_PIX_FMT_GBRAP10
Definition: pixfmt.h:419
static const AVFilterPad cas_inputs[]
Definition: vf_cas.c:260
#define AV_PIX_FMT_YUVA422P10
Definition: pixfmt.h:437
const char * desc
Definition: libsvtav1.c:79
planar YUV 4:4:4, 24bpp, (1 Cr & Cb sample per 1x1 Y samples)
Definition: pixfmt.h:71
misc image utilities
Main libavfilter public API header.
const char * g
Definition: vf_curves.c:115
planar GBR 4:4:4 24bpp
Definition: pixfmt.h:168
#define AV_PIX_FMT_GBRP10
Definition: pixfmt.h:415
The reader does not expect b to be semantically here and if the code is changed by maybe adding a a division or other the signedness will almost certainly be mistaken To avoid this confusion a new type was SUINT is the C unsigned type but it holds a signed int to use the same example SUINT a
Definition: undefined.txt:36
#define AV_PIX_FMT_GRAY9
Definition: pixfmt.h:379
#define AV_PIX_FMT_YUV420P12
Definition: pixfmt.h:403
GLfloat v0
Definition: opengl_enc.c:106
AVFrame * ff_get_video_buffer(AVFilterLink *link, int w, int h)
Request a picture buffer with a specific set of permissions.
Definition: video.c:99
uint8_t log2_chroma_w
Amount to shift the luma width right to find the chroma width.
Definition: pixdesc.h:92
AVFilterFormats * ff_make_format_list(const int *fmts)
Create a list of supported formats.
Definition: formats.c:283
#define AV_PIX_FMT_GRAY10
Definition: pixfmt.h:380
static av_cold int config_input(AVFilterLink *inlink)
Definition: vf_cas.c:242
#define AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC
Some filters support a generic "enable" expression option that can be used to enable or disable a fil...
Definition: avfilter.h:125
const char * name
Pad name.
Definition: internal.h:60
#define AV_PIX_FMT_GRAY12
Definition: pixfmt.h:381
int ff_filter_frame(AVFilterLink *link, AVFrame *frame)
Send a frame of data to the next filter.
Definition: avfilter.c:1091
static int filter_frame(AVFilterLink *inlink, AVFrame *in)
Definition: vf_cas.c:181
planar YUV 4:2:0, 20bpp, (1 Cr & Cb sample per 2x2 Y & A samples)
Definition: pixfmt.h:101
AVComponentDescriptor comp[4]
Parameters that describe how pixels are packed.
Definition: pixdesc.h:117
uint8_t
int planewidth[4]
Definition: vf_cas.c:35
#define av_cold
Definition: attributes.h:88
AVOptions.
#define f(width, name)
Definition: cbs_vp9.c:255
Undefined Behavior In the C some operations are like signed integer dereferencing freed accessing outside allocated Undefined Behavior must not occur in a C it is not safe even if the output of undefined operations is unused The unsafety may seem nit picking but Optimizing compilers have in fact optimized code on the assumption that no undefined Behavior occurs Optimizing code based on wrong assumptions can and has in some cases lead to effects beyond the output of computations The signed integer overflow problem in speed critical code Code which is highly optimized and works with signed integers sometimes has the problem that often the output of the computation does not c
Definition: undefined.txt:32
#define AV_PIX_FMT_YUVA420P9
Definition: pixfmt.h:433
#define AV_PIX_FMT_GBRP9
Definition: pixfmt.h:414
planar YUV 4:4:0 full scale (JPEG), deprecated in favor of AV_PIX_FMT_YUV440P and setting color_range...
Definition: pixfmt.h:100
#define FFMIN3(a, b, c)
Definition: common.h:97
planar YUV 4:2:2, 16bpp, full scale (JPEG), deprecated in favor of AV_PIX_FMT_YUV422P and setting col...
Definition: pixfmt.h:79
#define AV_PIX_FMT_YUV444P16
Definition: pixfmt.h:412
#define max(a, b)
Definition: cuda_runtime.h:33
#define AV_PIX_FMT_YUV422P12
Definition: pixfmt.h:404
#define AV_PIX_FMT_YUVA420P16
Definition: pixfmt.h:441
A filter pad used for either input or output.
Definition: internal.h:54
#define src
Definition: vp8dsp.c:254
planar YUV 4:2:2 24bpp, (1 Cr & Cb sample per 2x1 Y & A samples)
Definition: pixfmt.h:176
int ff_set_common_formats(AVFilterContext *ctx, AVFilterFormats *formats)
A helper for query_formats() which sets all links to the same list of formats.
Definition: formats.c:600
uint8_t log2_chroma_h
Amount to shift the luma height right to find the chroma height.
Definition: pixdesc.h:101
#define OFFSET(x)
Definition: vf_cas.c:278
static float lerpf(float v0, float v1, float f)
Definition: vf_cas.c:43
void av_frame_free(AVFrame **frame)
Free the frame and any dynamically allocated objects in it, e.g.
Definition: frame.c:203
#define NULL_IF_CONFIG_SMALL(x)
Return NULL if CONFIG_SMALL is true, otherwise the argument without modification. ...
Definition: internal.h:153
int nb_planes
Definition: vf_cas.c:31
int ff_filter_process_command(AVFilterContext *ctx, const char *cmd, const char *arg, char *res, int res_len, int flags)
Generic processing of user supplied commands that are set in the same way as the filter options...
Definition: avfilter.c:885
void * priv
private data for use by the filter
Definition: avfilter.h:353
#define AVFILTER_FLAG_SLICE_THREADS
The filter supports multithreading by splitting frames into multiple parts and processing them concur...
Definition: avfilter.h:116
#define AV_PIX_FMT_YUVA444P16
Definition: pixfmt.h:443
AVFilter ff_vf_cas
Definition: vf_cas.c:289
const char * arg
Definition: jacosubdec.c:66
#define AV_PIX_FMT_GBRAP12
Definition: pixfmt.h:420
#define AV_PIX_FMT_YUV444P10
Definition: pixfmt.h:402
#define FFMAX(a, b)
Definition: common.h:94
#define AV_PIX_FMT_GBRAP16
Definition: pixfmt.h:421
planar YUV 4:2:2, 16bpp, (1 Cr & Cb sample per 2x1 Y samples)
Definition: pixfmt.h:70
#define AV_PIX_FMT_YUV422P9
Definition: pixfmt.h:397
uint8_t nb_components
The number of components each pixel has, (1-4)
Definition: pixdesc.h:83
#define b
Definition: input.c:41
#define AV_PIX_FMT_GBRP16
Definition: pixfmt.h:418
int ff_filter_get_nb_threads(AVFilterContext *ctx)
Get number of threads for current filter instance.
Definition: avfilter.c:800
#define AV_PIX_FMT_GRAY16
Definition: pixfmt.h:383
#define FFMIN(a, b)
Definition: common.h:96
planar YUV 4:2:0, 12bpp, full scale (JPEG), deprecated in favor of AV_PIX_FMT_YUV420P and setting col...
Definition: pixfmt.h:78
#define AV_PIX_FMT_YUVA444P12
Definition: pixfmt.h:440
uint8_t w
Definition: llviddspenc.c:38
static int cas_slice16(AVFilterContext *avctx, void *arg, int jobnr, int nb_jobs)
Definition: vf_cas.c:114
AVFormatContext * ctx
Definition: movenc.c:48
#define s(width, name)
Definition: cbs_vp9.c:257
#define AV_PIX_FMT_YUVA444P10
Definition: pixfmt.h:438
static const AVOption cas_options[]
Definition: vf_cas.c:281
#define AV_PIX_FMT_YUV444P9
Definition: pixfmt.h:398
#define AV_PIX_FMT_GBRP14
Definition: pixfmt.h:417
static const AVFilterPad outputs[]
Definition: af_acontrast.c:203
int depth
Definition: vf_cas.c:33
static av_cold int query_formats(AVFilterContext *avctx)
Definition: vf_cas.c:204
#define AV_PIX_FMT_YUV420P16
Definition: pixfmt.h:410
#define AV_PIX_FMT_YUV420P14
Definition: pixfmt.h:407
int linesize[AV_NUM_DATA_POINTERS]
For video, size in bytes of each picture line.
Definition: frame.h:339
planar YUV 4:4:4 32bpp, (1 Cr & Cb sample per 1x1 Y & A samples)
Definition: pixfmt.h:177
Descriptor that unambiguously describes how the bits of a pixel are stored in the up to 4 data planes...
Definition: pixdesc.h:81
#define AV_PIX_FMT_GRAY14
Definition: pixfmt.h:382
static int cas_slice8(AVFilterContext *avctx, void *arg, int jobnr, int nb_jobs)
Definition: vf_cas.c:48
int planes
Definition: vf_cas.c:30
these buffered frames must be flushed immediately if a new input produces new the filter must not call request_frame to get more It must just process the frame or queue it The task of requesting more frames is left to the filter s request_frame method or the application If a filter has several inputs
#define AV_PIX_FMT_YUV420P10
Definition: pixfmt.h:399
planar YUV 4:1:0, 9bpp, (1 Cr & Cb sample per 4x4 Y samples)
Definition: pixfmt.h:72
Describe the class of an AVClass context structure.
Definition: log.h:67
static const AVFilterPad cas_outputs[]
Definition: vf_cas.c:270
Filter definition.
Definition: avfilter.h:144
const char * name
Filter name.
Definition: avfilter.h:148
#define AV_PIX_FMT_YUV440P12
Definition: pixfmt.h:405
#define AV_PIX_FMT_YUV420P9
Definition: pixfmt.h:396
AVFilterLink ** outputs
array of pointers to output links
Definition: avfilter.h:350
static int weight(int i, int blen, int offset)
Definition: diracdec.c:1560
#define AV_PIX_FMT_YUV422P14
Definition: pixfmt.h:408
#define AV_PIX_FMT_GBRP12
Definition: pixfmt.h:416
#define flags(name, subs,...)
Definition: cbs_av1.c:560
AVFilterInternal * internal
An opaque struct for libavfilter internal use.
Definition: avfilter.h:378
#define AV_PIX_FMT_YUV422P10
Definition: pixfmt.h:400
#define AV_PIX_FMT_YUV444P12
Definition: pixfmt.h:406
uint8_t * data[AV_NUM_DATA_POINTERS]
pointer to the picture/channel planes.
Definition: frame.h:322
The exact code depends on how similar the blocks are and how related they are to the and needs to apply these operations to the correct inlink or outlink if there are several Macros are available to factor that when no extra processing is inlink
int planeheight[4]
Definition: vf_cas.c:34
AVFrame * in
Definition: vf_cas.c:37
int
planar YUV 4:2:0, 12bpp, (1 Cr & Cb sample per 2x2 Y samples)
Definition: pixfmt.h:66
Y , 8bpp.
Definition: pixfmt.h:74
planar GBRA 4:4:4:4 32bpp
Definition: pixfmt.h:215
#define AV_PIX_FMT_YUVA444P9
Definition: pixfmt.h:435
planar YUV 4:4:4, 24bpp, full scale (JPEG), deprecated in favor of AV_PIX_FMT_YUV444P and setting col...
Definition: pixfmt.h:80
planar YUV 4:1:1, 12bpp, (1 Cr & Cb sample per 4x1 Y samples)
Definition: pixfmt.h:73
avfilter_execute_func * execute
Definition: internal.h:144
static int slice_end(AVCodecContext *avctx, AVFrame *pict)
Handle slice ends.
Definition: mpeg12dec.c:2039
float strength
Definition: vf_cas.c:29
A list of supported formats for one end of a filter link.
Definition: formats.h:64
planar YUV 4:1:1, 12bpp, (1 Cr & Cb sample per 4x1 Y samples) full scale (JPEG), deprecated in favor ...
Definition: pixfmt.h:258
An instance of a filter.
Definition: avfilter.h:338
int height
Definition: frame.h:366
FILE * out
Definition: movenc.c:54
static int process_command(AVFilterContext *ctx, const char *cmd, const char *args, char *res, int res_len, int flags)
Definition: af_afftdn.c:1374
planar YUV 4:4:0 (1 Cr & Cb sample per 1x2 Y samples)
Definition: pixfmt.h:99
formats
Definition: signature.h:48
void av_image_copy_plane(uint8_t *dst, int dst_linesize, const uint8_t *src, int src_linesize, int bytewidth, int height)
Copy image plane from src to dst.
Definition: imgutils.c:373
internal API functions
Filter the word “frame” indicates either a video frame or a group of audio as stored in an AVFrame structure Format for each input and each output the list of supported formats For video that means pixel format For audio that means channel sample they are references to shared objects When the negotiation mechanism computes the intersection of the formats supported at each end of a all references to both lists are replaced with a reference to the intersection And when a single format is eventually chosen for a link amongst the remaining all references to the list are updated That means that if a filter requires that its input and output have the same format amongst a supported all it has to do is use a reference to the same list of formats query_formats can leave some formats unset and return AVERROR(EAGAIN) to cause the negotiation mechanism toagain later.That can be used by filters with complex requirements to use the format negotiated on one link to set the formats supported on another.Frame references ownership and permissions
int depth
Number of bits in the component.
Definition: pixdesc.h:58
AVPixelFormat
Pixel format.
Definition: pixfmt.h:64
int(* do_slice)(AVFilterContext *s, void *arg, int jobnr, int nb_jobs)
Definition: vf_cas.c:39
#define AV_PIX_FMT_YUV422P16
Definition: pixfmt.h:411
int av_frame_copy_props(AVFrame *dst, const AVFrame *src)
Copy only "metadata" fields from src to dst.
Definition: frame.c:671
int i
Definition: input.c:407
#define FFMAX3(a, b, c)
Definition: common.h:95
#define AV_PIX_FMT_YUVA422P12
Definition: pixfmt.h:439
#define AV_CEIL_RSHIFT(a, b)
Definition: common.h:58
static av_always_inline av_const unsigned av_clip_uintp2_c(int a, int p)
Clip a signed integer to an unsigned power of two range.
Definition: common.h:229