1 .. SPDX-License-Identifier: GPL-2.0+ 1 .. SPDX-License-Identifier: GPL-2.0+
2 2
3 =================================== 3 ===================================
4 Arm Framebuffer Compression (AFBC) 4 Arm Framebuffer Compression (AFBC)
5 =================================== 5 ===================================
6 6
7 AFBC is a proprietary lossless image compressi 7 AFBC is a proprietary lossless image compression protocol and format.
8 It provides fine-grained random access and min 8 It provides fine-grained random access and minimizes the amount of
9 data transferred between IP blocks. 9 data transferred between IP blocks.
10 10
11 AFBC can be enabled on drivers which support i 11 AFBC can be enabled on drivers which support it via use of the AFBC
12 format modifiers defined in drm_fourcc.h. See 12 format modifiers defined in drm_fourcc.h. See DRM_FORMAT_MOD_ARM_AFBC(*).
13 13
14 All users of the AFBC modifiers must follow th 14 All users of the AFBC modifiers must follow the usage guidelines laid
15 out in this document, to ensure compatibility 15 out in this document, to ensure compatibility across different AFBC
16 producers and consumers. 16 producers and consumers.
17 17
18 Components and Ordering 18 Components and Ordering
19 ======================= 19 =======================
20 20
21 AFBC streams can contain several components - 21 AFBC streams can contain several components - where a component
22 corresponds to a color channel (i.e. R, G, B, 22 corresponds to a color channel (i.e. R, G, B, X, A, Y, Cb, Cr).
23 The assignment of input/output color channels 23 The assignment of input/output color channels must be consistent
24 between the encoder and the decoder for correc 24 between the encoder and the decoder for correct operation, otherwise
25 the consumer will interpret the decoded data i 25 the consumer will interpret the decoded data incorrectly.
26 26
27 Furthermore, when the lossless colorspace tran 27 Furthermore, when the lossless colorspace transform is used
28 (AFBC_FORMAT_MOD_YTR, which should be enabled 28 (AFBC_FORMAT_MOD_YTR, which should be enabled for RGB buffers for
29 maximum compression efficiency), the component 29 maximum compression efficiency), the component order must be:
30 30
31 * Component 0: R 31 * Component 0: R
32 * Component 1: G 32 * Component 1: G
33 * Component 2: B 33 * Component 2: B
34 34
35 The component ordering is communicated via the 35 The component ordering is communicated via the fourcc code in the
36 fourcc:modifier pair. In general, component '0 36 fourcc:modifier pair. In general, component '0' is considered to
37 reside in the least-significant bits of the co 37 reside in the least-significant bits of the corresponding linear
38 format. For example, COMP(bits): 38 format. For example, COMP(bits):
39 39
40 * DRM_FORMAT_ABGR8888 40 * DRM_FORMAT_ABGR8888
41 41
42 * Component 0: R(8) 42 * Component 0: R(8)
43 * Component 1: G(8) 43 * Component 1: G(8)
44 * Component 2: B(8) 44 * Component 2: B(8)
45 * Component 3: A(8) 45 * Component 3: A(8)
46 46
47 * DRM_FORMAT_BGR888 47 * DRM_FORMAT_BGR888
48 48
49 * Component 0: R(8) 49 * Component 0: R(8)
50 * Component 1: G(8) 50 * Component 1: G(8)
51 * Component 2: B(8) 51 * Component 2: B(8)
52 52
53 * DRM_FORMAT_YUYV 53 * DRM_FORMAT_YUYV
54 54
55 * Component 0: Y(8) 55 * Component 0: Y(8)
56 * Component 1: Cb(8, 2x1 subsampled) 56 * Component 1: Cb(8, 2x1 subsampled)
57 * Component 2: Cr(8, 2x1 subsampled) 57 * Component 2: Cr(8, 2x1 subsampled)
58 58
59 In AFBC, 'X' components are not treated any di 59 In AFBC, 'X' components are not treated any differently from any other
60 component. Therefore, an AFBC buffer with four 60 component. Therefore, an AFBC buffer with fourcc DRM_FORMAT_XBGR8888
61 encodes with 4 components, like so: 61 encodes with 4 components, like so:
62 62
63 * DRM_FORMAT_XBGR8888 63 * DRM_FORMAT_XBGR8888
64 64
65 * Component 0: R(8) 65 * Component 0: R(8)
66 * Component 1: G(8) 66 * Component 1: G(8)
67 * Component 2: B(8) 67 * Component 2: B(8)
68 * Component 3: X(8) 68 * Component 3: X(8)
69 69
70 Please note, however, that the inclusion of a 70 Please note, however, that the inclusion of a "wasted" 'X' channel is
71 bad for compression efficiency, and so it's re 71 bad for compression efficiency, and so it's recommended to avoid
72 formats containing 'X' bits. If a fourth compo 72 formats containing 'X' bits. If a fourth component is
73 required/expected by the encoder/decoder, then 73 required/expected by the encoder/decoder, then it is recommended to
74 instead use an equivalent format with alpha, s 74 instead use an equivalent format with alpha, setting all alpha bits to
75 '1'. If there is no requirement for a fourth c 75 '1'. If there is no requirement for a fourth component, then a format
76 which doesn't include alpha can be used, e.g. 76 which doesn't include alpha can be used, e.g. DRM_FORMAT_BGR888.
77 77
78 Number of Planes 78 Number of Planes
79 ================ 79 ================
80 80
81 Formats which are typically multi-planar in li 81 Formats which are typically multi-planar in linear layouts (e.g. YUV
82 420), can be encoded into one, or multiple, AF 82 420), can be encoded into one, or multiple, AFBC planes. As with
83 component order, the encoder and decoder must 83 component order, the encoder and decoder must agree about the number
84 of planes in order to correctly decode the buf 84 of planes in order to correctly decode the buffer. The fourcc code is
85 used to determine the number of encoded planes 85 used to determine the number of encoded planes in an AFBC buffer,
86 matching the number of planes for the linear ( 86 matching the number of planes for the linear (unmodified) format.
87 Within each plane, the component ordering also 87 Within each plane, the component ordering also follows the fourcc
88 code: 88 code:
89 89
90 For example: 90 For example:
91 91
92 * DRM_FORMAT_YUYV: nplanes = 1 92 * DRM_FORMAT_YUYV: nplanes = 1
93 93
94 * Plane 0: 94 * Plane 0:
95 95
96 * Component 0: Y(8) 96 * Component 0: Y(8)
97 * Component 1: Cb(8, 2x1 subsampled) 97 * Component 1: Cb(8, 2x1 subsampled)
98 * Component 2: Cr(8, 2x1 subsampled) 98 * Component 2: Cr(8, 2x1 subsampled)
99 99
100 * DRM_FORMAT_NV12: nplanes = 2 100 * DRM_FORMAT_NV12: nplanes = 2
101 101
102 * Plane 0: 102 * Plane 0:
103 103
104 * Component 0: Y(8) 104 * Component 0: Y(8)
105 105
106 * Plane 1: 106 * Plane 1:
107 107
108 * Component 0: Cb(8, 2x1 subsampled) 108 * Component 0: Cb(8, 2x1 subsampled)
109 * Component 1: Cr(8, 2x1 subsampled) 109 * Component 1: Cr(8, 2x1 subsampled)
110 110
111 Cross-device interoperability 111 Cross-device interoperability
112 ============================= 112 =============================
113 113
114 For maximum compatibility across devices, the 114 For maximum compatibility across devices, the table below defines
115 canonical formats for use between AFBC-enabled 115 canonical formats for use between AFBC-enabled devices. Formats which
116 are listed here must be used exactly as specif 116 are listed here must be used exactly as specified when using the AFBC
117 modifiers. Formats which are not listed should 117 modifiers. Formats which are not listed should be avoided.
118 118
119 .. flat-table:: AFBC formats 119 .. flat-table:: AFBC formats
120 120
121 * - Fourcc code 121 * - Fourcc code
122 - Description 122 - Description
123 - Planes/Components 123 - Planes/Components
124 124
125 * - DRM_FORMAT_ABGR2101010 125 * - DRM_FORMAT_ABGR2101010
126 - 10-bit per component RGB, with 2-bit al 126 - 10-bit per component RGB, with 2-bit alpha
127 - Plane 0: 4 components 127 - Plane 0: 4 components
128 * Component 0: R(10) 128 * Component 0: R(10)
129 * Component 1: G(10) 129 * Component 1: G(10)
130 * Component 2: B(10) 130 * Component 2: B(10)
131 * Component 3: A(2) 131 * Component 3: A(2)
132 132
133 * - DRM_FORMAT_ABGR8888 133 * - DRM_FORMAT_ABGR8888
134 - 8-bit per component RGB, with 8-bit alp 134 - 8-bit per component RGB, with 8-bit alpha
135 - Plane 0: 4 components 135 - Plane 0: 4 components
136 * Component 0: R(8) 136 * Component 0: R(8)
137 * Component 1: G(8) 137 * Component 1: G(8)
138 * Component 2: B(8) 138 * Component 2: B(8)
139 * Component 3: A(8) 139 * Component 3: A(8)
140 140
141 * - DRM_FORMAT_BGR888 141 * - DRM_FORMAT_BGR888
142 - 8-bit per component RGB 142 - 8-bit per component RGB
143 - Plane 0: 3 components 143 - Plane 0: 3 components
144 * Component 0: R(8) 144 * Component 0: R(8)
145 * Component 1: G(8) 145 * Component 1: G(8)
146 * Component 2: B(8) 146 * Component 2: B(8)
147 147
148 * - DRM_FORMAT_BGR565 148 * - DRM_FORMAT_BGR565
149 - 5/6-bit per component RGB 149 - 5/6-bit per component RGB
150 - Plane 0: 3 components 150 - Plane 0: 3 components
151 * Component 0: R(5) 151 * Component 0: R(5)
152 * Component 1: G(6) 152 * Component 1: G(6)
153 * Component 2: B(5) 153 * Component 2: B(5)
154 154
155 * - DRM_FORMAT_ABGR1555 155 * - DRM_FORMAT_ABGR1555
156 - 5-bit per component RGB, with 1-bit alp 156 - 5-bit per component RGB, with 1-bit alpha
157 - Plane 0: 4 components 157 - Plane 0: 4 components
158 * Component 0: R(5) 158 * Component 0: R(5)
159 * Component 1: G(5) 159 * Component 1: G(5)
160 * Component 2: B(5) 160 * Component 2: B(5)
161 * Component 3: A(1) 161 * Component 3: A(1)
162 162
163 * - DRM_FORMAT_VUY888 163 * - DRM_FORMAT_VUY888
164 - 8-bit per component YCbCr 444, single p 164 - 8-bit per component YCbCr 444, single plane
165 - Plane 0: 3 components 165 - Plane 0: 3 components
166 * Component 0: Y(8) 166 * Component 0: Y(8)
167 * Component 1: Cb(8) 167 * Component 1: Cb(8)
168 * Component 2: Cr(8) 168 * Component 2: Cr(8)
169 169
170 * - DRM_FORMAT_VUY101010 170 * - DRM_FORMAT_VUY101010
171 - 10-bit per component YCbCr 444, single 171 - 10-bit per component YCbCr 444, single plane
172 - Plane 0: 3 components 172 - Plane 0: 3 components
173 * Component 0: Y(10) 173 * Component 0: Y(10)
174 * Component 1: Cb(10) 174 * Component 1: Cb(10)
175 * Component 2: Cr(10) 175 * Component 2: Cr(10)
176 176
177 * - DRM_FORMAT_YUYV 177 * - DRM_FORMAT_YUYV
178 - 8-bit per component YCbCr 422, single p 178 - 8-bit per component YCbCr 422, single plane
179 - Plane 0: 3 components 179 - Plane 0: 3 components
180 * Component 0: Y(8) 180 * Component 0: Y(8)
181 * Component 1: Cb(8, 2x1 subsamp 181 * Component 1: Cb(8, 2x1 subsampled)
182 * Component 2: Cr(8, 2x1 subsamp 182 * Component 2: Cr(8, 2x1 subsampled)
183 183
184 * - DRM_FORMAT_NV16 184 * - DRM_FORMAT_NV16
185 - 8-bit per component YCbCr 422, two plan 185 - 8-bit per component YCbCr 422, two plane
186 - Plane 0: 1 component 186 - Plane 0: 1 component
187 * Component 0: Y(8) 187 * Component 0: Y(8)
188 Plane 1: 2 components 188 Plane 1: 2 components
189 * Component 0: Cb(8, 2x1 subsamp 189 * Component 0: Cb(8, 2x1 subsampled)
190 * Component 1: Cr(8, 2x1 subsamp 190 * Component 1: Cr(8, 2x1 subsampled)
191 191
192 * - DRM_FORMAT_Y210 192 * - DRM_FORMAT_Y210
193 - 10-bit per component YCbCr 422, single 193 - 10-bit per component YCbCr 422, single plane
194 - Plane 0: 3 components 194 - Plane 0: 3 components
195 * Component 0: Y(10) 195 * Component 0: Y(10)
196 * Component 1: Cb(10, 2x1 subsam 196 * Component 1: Cb(10, 2x1 subsampled)
197 * Component 2: Cr(10, 2x1 subsam 197 * Component 2: Cr(10, 2x1 subsampled)
198 198
199 * - DRM_FORMAT_P210 199 * - DRM_FORMAT_P210
200 - 10-bit per component YCbCr 422, two pla 200 - 10-bit per component YCbCr 422, two plane
201 - Plane 0: 1 component 201 - Plane 0: 1 component
202 * Component 0: Y(10) 202 * Component 0: Y(10)
203 Plane 1: 2 components 203 Plane 1: 2 components
204 * Component 0: Cb(10, 2x1 subsam 204 * Component 0: Cb(10, 2x1 subsampled)
205 * Component 1: Cr(10, 2x1 subsam 205 * Component 1: Cr(10, 2x1 subsampled)
206 206
207 * - DRM_FORMAT_YUV420_8BIT 207 * - DRM_FORMAT_YUV420_8BIT
208 - 8-bit per component YCbCr 420, single p 208 - 8-bit per component YCbCr 420, single plane
209 - Plane 0: 3 components 209 - Plane 0: 3 components
210 * Component 0: Y(8) 210 * Component 0: Y(8)
211 * Component 1: Cb(8, 2x2 subsamp 211 * Component 1: Cb(8, 2x2 subsampled)
212 * Component 2: Cr(8, 2x2 subsamp 212 * Component 2: Cr(8, 2x2 subsampled)
213 213
214 * - DRM_FORMAT_YUV420_10BIT 214 * - DRM_FORMAT_YUV420_10BIT
215 - 10-bit per component YCbCr 420, single 215 - 10-bit per component YCbCr 420, single plane
216 - Plane 0: 3 components 216 - Plane 0: 3 components
217 * Component 0: Y(10) 217 * Component 0: Y(10)
218 * Component 1: Cb(10, 2x2 subsam 218 * Component 1: Cb(10, 2x2 subsampled)
219 * Component 2: Cr(10, 2x2 subsam 219 * Component 2: Cr(10, 2x2 subsampled)
220 220
221 * - DRM_FORMAT_NV12 221 * - DRM_FORMAT_NV12
222 - 8-bit per component YCbCr 420, two plan 222 - 8-bit per component YCbCr 420, two plane
223 - Plane 0: 1 component 223 - Plane 0: 1 component
224 * Component 0: Y(8) 224 * Component 0: Y(8)
225 Plane 1: 2 components 225 Plane 1: 2 components
226 * Component 0: Cb(8, 2x2 subsamp 226 * Component 0: Cb(8, 2x2 subsampled)
227 * Component 1: Cr(8, 2x2 subsamp 227 * Component 1: Cr(8, 2x2 subsampled)
228 228
229 * - DRM_FORMAT_P010 229 * - DRM_FORMAT_P010
230 - 10-bit per component YCbCr 420, two pla 230 - 10-bit per component YCbCr 420, two plane
231 - Plane 0: 1 component 231 - Plane 0: 1 component
232 * Component 0: Y(10) 232 * Component 0: Y(10)
233 Plane 1: 2 components 233 Plane 1: 2 components
234 * Component 0: Cb(10, 2x2 subsam 234 * Component 0: Cb(10, 2x2 subsampled)
235 * Component 1: Cr(10, 2x2 subsam 235 * Component 1: Cr(10, 2x2 subsampled)
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