1 .. SPDX-License-Identifier: GFDL-1.1-no-invari 1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
2 2
3 .. _yuv-formats: 3 .. _yuv-formats:
4 4
5 *********** 5 ***********
6 YUV Formats 6 YUV Formats
7 *********** 7 ***********
8 8
9 YUV is the format native to TV broadcast and c 9 YUV is the format native to TV broadcast and composite video signals. It
10 separates the brightness information (Y) from 10 separates the brightness information (Y) from the color information (U
11 and V or Cb and Cr). The color information con 11 and V or Cb and Cr). The color information consists of red and blue
12 *color difference* signals, this way the green 12 *color difference* signals, this way the green component can be
13 reconstructed by subtracting from the brightne 13 reconstructed by subtracting from the brightness component. See
14 :ref:`colorspaces` for conversion examples. YU 14 :ref:`colorspaces` for conversion examples. YUV was chosen because
15 early television would only transmit brightnes 15 early television would only transmit brightness information. To add
16 color in a way compatible with existing receiv 16 color in a way compatible with existing receivers a new signal carrier
17 was added to transmit the color difference sig 17 was added to transmit the color difference signals.
18 18
19 19
20 Subsampling 20 Subsampling
21 =========== 21 ===========
22 22
23 YUV formats commonly encode images with a lowe 23 YUV formats commonly encode images with a lower resolution for the chroma
24 components than for the luma component. This c 24 components than for the luma component. This compression technique, taking
25 advantage of the human eye being more sensitiv 25 advantage of the human eye being more sensitive to luminance than color
26 differences, is called chroma subsampling. 26 differences, is called chroma subsampling.
27 27
28 While many combinations of subsampling factors 28 While many combinations of subsampling factors in the horizontal and vertical
29 direction are possible, common factors are 1 ( 29 direction are possible, common factors are 1 (no subsampling), 2 and 4, with
30 horizontal subsampling always larger than or e 30 horizontal subsampling always larger than or equal to vertical subsampling.
31 Common combinations are named as follows. 31 Common combinations are named as follows.
32 32
33 - `4:4:4`: No subsampling 33 - `4:4:4`: No subsampling
34 - `4:2:2`: Horizontal subsampling by 2, no ver 34 - `4:2:2`: Horizontal subsampling by 2, no vertical subsampling
35 - `4:2:0`: Horizontal subsampling by 2, vertic 35 - `4:2:0`: Horizontal subsampling by 2, vertical subsampling by 2
36 - `4:1:1`: Horizontal subsampling by 4, no ver 36 - `4:1:1`: Horizontal subsampling by 4, no vertical subsampling
37 - `4:1:0`: Horizontal subsampling by 4, vertic 37 - `4:1:0`: Horizontal subsampling by 4, vertical subsampling by 4
38 38
39 Subsampling the chroma component effectively c 39 Subsampling the chroma component effectively creates chroma values that can be
40 located in different spatial locations: 40 located in different spatial locations:
41 41
42 - .. _yuv-chroma-centered: 42 - .. _yuv-chroma-centered:
43 43
44 The subsampled chroma value may be calculate 44 The subsampled chroma value may be calculated by simply averaging the chroma
45 value of two consecutive pixels. It effectiv 45 value of two consecutive pixels. It effectively models the chroma of a pixel
46 sited between the two original pixels. This 46 sited between the two original pixels. This is referred to as centered or
47 interstitially sited chroma. 47 interstitially sited chroma.
48 48
49 - .. _yuv-chroma-cosited: 49 - .. _yuv-chroma-cosited:
50 50
51 The other option is to subsample chroma valu 51 The other option is to subsample chroma values in a way that place them in
52 the same spatial sites as the pixels. This m 52 the same spatial sites as the pixels. This may be performed by skipping every
53 other chroma sample (creating aliasing artif 53 other chroma sample (creating aliasing artifacts), or with filters using an
54 odd number of taps. This is referred to as c 54 odd number of taps. This is referred to as co-sited chroma.
55 55
56 The following examples show different combinat 56 The following examples show different combination of chroma siting in a 4x4
57 image. 57 image.
58 58
59 .. flat-table:: 4:2:2 subsampling, interstitia 59 .. flat-table:: 4:2:2 subsampling, interstitially sited
60 :header-rows: 1 60 :header-rows: 1
61 :stub-columns: 1 61 :stub-columns: 1
62 62
63 * - 63 * -
64 - 0 64 - 0
65 - 65 -
66 - 1 66 - 1
67 - 67 -
68 - 2 68 - 2
69 - 69 -
70 - 3 70 - 3
71 * - 0 71 * - 0
72 - Y 72 - Y
73 - C 73 - C
74 - Y 74 - Y
75 - 75 -
76 - Y 76 - Y
77 - C 77 - C
78 - Y 78 - Y
79 * - 1 79 * - 1
80 - Y 80 - Y
81 - C 81 - C
82 - Y 82 - Y
83 - 83 -
84 - Y 84 - Y
85 - C 85 - C
86 - Y 86 - Y
87 * - 2 87 * - 2
88 - Y 88 - Y
89 - C 89 - C
90 - Y 90 - Y
91 - 91 -
92 - Y 92 - Y
93 - C 93 - C
94 - Y 94 - Y
95 * - 3 95 * - 3
96 - Y 96 - Y
97 - C 97 - C
98 - Y 98 - Y
99 - 99 -
100 - Y 100 - Y
101 - C 101 - C
102 - Y 102 - Y
103 103
104 .. flat-table:: 4:2:2 subsampling, co-sited 104 .. flat-table:: 4:2:2 subsampling, co-sited
105 :header-rows: 1 105 :header-rows: 1
106 :stub-columns: 1 106 :stub-columns: 1
107 107
108 * - 108 * -
109 - 0 109 - 0
110 - 110 -
111 - 1 111 - 1
112 - 112 -
113 - 2 113 - 2
114 - 114 -
115 - 3 115 - 3
116 * - 0 116 * - 0
117 - Y/C 117 - Y/C
118 - 118 -
119 - Y 119 - Y
120 - 120 -
121 - Y/C 121 - Y/C
122 - 122 -
123 - Y 123 - Y
124 * - 1 124 * - 1
125 - Y/C 125 - Y/C
126 - 126 -
127 - Y 127 - Y
128 - 128 -
129 - Y/C 129 - Y/C
130 - 130 -
131 - Y 131 - Y
132 * - 2 132 * - 2
133 - Y/C 133 - Y/C
134 - 134 -
135 - Y 135 - Y
136 - 136 -
137 - Y/C 137 - Y/C
138 - 138 -
139 - Y 139 - Y
140 * - 3 140 * - 3
141 - Y/C 141 - Y/C
142 - 142 -
143 - Y 143 - Y
144 - 144 -
145 - Y/C 145 - Y/C
146 - 146 -
147 - Y 147 - Y
148 148
149 .. flat-table:: 4:2:0 subsampling, horizontall 149 .. flat-table:: 4:2:0 subsampling, horizontally interstitially sited, vertically co-sited
150 :header-rows: 1 150 :header-rows: 1
151 :stub-columns: 1 151 :stub-columns: 1
152 152
153 * - 153 * -
154 - 0 154 - 0
155 - 155 -
156 - 1 156 - 1
157 - 157 -
158 - 2 158 - 2
159 - 159 -
160 - 3 160 - 3
161 * - 0 161 * - 0
162 - Y 162 - Y
163 - C 163 - C
164 - Y 164 - Y
165 - 165 -
166 - Y 166 - Y
167 - C 167 - C
168 - Y 168 - Y
169 * - 1 169 * - 1
170 - Y 170 - Y
171 - 171 -
172 - Y 172 - Y
173 - 173 -
174 - Y 174 - Y
175 - 175 -
176 - Y 176 - Y
177 * - 2 177 * - 2
178 - Y 178 - Y
179 - C 179 - C
180 - Y 180 - Y
181 - 181 -
182 - Y 182 - Y
183 - C 183 - C
184 - Y 184 - Y
185 * - 3 185 * - 3
186 - Y 186 - Y
187 - 187 -
188 - Y 188 - Y
189 - 189 -
190 - Y 190 - Y
191 - 191 -
192 - Y 192 - Y
193 193
194 .. flat-table:: 4:1:0 subsampling, horizontall 194 .. flat-table:: 4:1:0 subsampling, horizontally and vertically interstitially sited
195 :header-rows: 1 195 :header-rows: 1
196 :stub-columns: 1 196 :stub-columns: 1
197 197
198 * - 198 * -
199 - 0 199 - 0
200 - 200 -
201 - 1 201 - 1
202 - 202 -
203 - 2 203 - 2
204 - 204 -
205 - 3 205 - 3
206 * - 0 206 * - 0
207 - Y 207 - Y
208 - 208 -
209 - Y 209 - Y
210 - 210 -
211 - Y 211 - Y
212 - 212 -
213 - Y 213 - Y
214 * - 214 * -
215 - 215 -
216 - 216 -
217 - 217 -
218 - 218 -
219 - 219 -
220 - 220 -
221 - 221 -
222 * - 1 222 * - 1
223 - Y 223 - Y
224 - 224 -
225 - Y 225 - Y
226 - 226 -
227 - Y 227 - Y
228 - 228 -
229 - Y 229 - Y
230 * - 230 * -
231 - 231 -
232 - 232 -
233 - 233 -
234 - C 234 - C
235 - 235 -
236 - 236 -
237 - 237 -
238 * - 2 238 * - 2
239 - Y 239 - Y
240 - 240 -
241 - Y 241 - Y
242 - 242 -
243 - Y 243 - Y
244 - 244 -
245 - Y 245 - Y
246 * - 246 * -
247 - 247 -
248 - 248 -
249 - 249 -
250 - 250 -
251 - 251 -
252 - 252 -
253 - 253 -
254 * - 3 254 * - 3
255 - Y 255 - Y
256 - 256 -
257 - Y 257 - Y
258 - 258 -
259 - Y 259 - Y
260 - 260 -
261 - Y 261 - Y
262 262
263 263
264 .. toctree:: 264 .. toctree::
265 :maxdepth: 1 265 :maxdepth: 1
266 266
267 pixfmt-packed-yuv 267 pixfmt-packed-yuv
268 pixfmt-yuv-planar 268 pixfmt-yuv-planar
269 pixfmt-yuv-luma 269 pixfmt-yuv-luma
270 pixfmt-y8i 270 pixfmt-y8i
271 pixfmt-y12i 271 pixfmt-y12i
272 pixfmt-uv8 272 pixfmt-uv8
273 pixfmt-m420 273 pixfmt-m420
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