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