1 .. SPDX-License-Identifier: GPL-2.0 1 .. SPDX-License-Identifier: GPL-2.0
2 2
3 The Virtual Stateless Decoder Driver (visl) 3 The Virtual Stateless Decoder Driver (visl)
4 =========================================== 4 ===========================================
5 5
6 A virtual stateless decoder device for statele 6 A virtual stateless decoder device for stateless uAPI development
7 purposes. 7 purposes.
8 8
9 This tool's objective is to help the developme 9 This tool's objective is to help the development and testing of
10 userspace applications that use the V4L2 state 10 userspace applications that use the V4L2 stateless API to decode media.
11 11
12 A userspace implementation can use visl to run 12 A userspace implementation can use visl to run a decoding loop even when
13 no hardware is available or when the kernel uA 13 no hardware is available or when the kernel uAPI for the codec has not
14 been upstreamed yet. This can reveal bugs at a 14 been upstreamed yet. This can reveal bugs at an early stage.
15 15
16 This driver can also trace the contents of the 16 This driver can also trace the contents of the V4L2 controls submitted
17 to it. It can also dump the contents of the v 17 to it. It can also dump the contents of the vb2 buffers through a
18 debugfs interface. This is in many ways simila 18 debugfs interface. This is in many ways similar to the tracing
19 infrastructure available for other popular enc 19 infrastructure available for other popular encode/decode APIs out there
20 and can help develop a userspace application b 20 and can help develop a userspace application by using another (working)
21 one as a reference. 21 one as a reference.
22 22
23 .. note:: 23 .. note::
24 24
25 No actual decoding of video frames is 25 No actual decoding of video frames is performed by visl. The
26 V4L2 test pattern generator is used to 26 V4L2 test pattern generator is used to write various debug information
27 to the capture buffers instead. 27 to the capture buffers instead.
28 28
29 Module parameters 29 Module parameters
30 ----------------- 30 -----------------
31 31
32 - visl_debug: Activates debug info, printing v 32 - visl_debug: Activates debug info, printing various debug messages through
33 dprintk. Also controls whether per-frame deb 33 dprintk. Also controls whether per-frame debug info is shown. Defaults to off.
34 Note that enabling this feature can result i 34 Note that enabling this feature can result in slow performance through serial.
35 35
36 - visl_transtime_ms: Simulated process time in 36 - visl_transtime_ms: Simulated process time in milliseconds. Slowing down the
37 decoding speed can be useful for debugging. 37 decoding speed can be useful for debugging.
38 38
39 - visl_dprintk_frame_start, visl_dprintk_frame 39 - visl_dprintk_frame_start, visl_dprintk_frame_nframes: Dictates a range of
40 frames where dprintk is activated. This only 40 frames where dprintk is activated. This only controls the dprintk tracing on a
41 per-frame basis. Note that printing a lot of 41 per-frame basis. Note that printing a lot of data can be slow through serial.
42 42
43 - keep_bitstream_buffers: Controls whether bit 43 - keep_bitstream_buffers: Controls whether bitstream (i.e. OUTPUT) buffers are
44 kept after a decoding session. Defaults to f 44 kept after a decoding session. Defaults to false so as to reduce the amount of
45 clutter. keep_bitstream_buffers == false wor 45 clutter. keep_bitstream_buffers == false works well when live debugging the
46 client program with GDB. 46 client program with GDB.
47 47
48 - bitstream_trace_frame_start, bitstream_trace 48 - bitstream_trace_frame_start, bitstream_trace_nframes: Similar to
49 visl_dprintk_frame_start, visl_dprintk_nfram 49 visl_dprintk_frame_start, visl_dprintk_nframes, but controls the dumping of
50 buffer data through debugfs instead. 50 buffer data through debugfs instead.
51 51
52 - tpg_verbose: Write extra information on each <<
53 the API. When set to true, the output frames <<
54 as some information like pointers or queue s <<
55 <<
56 What is the default use case for this driver? 52 What is the default use case for this driver?
57 --------------------------------------------- 53 ---------------------------------------------
58 54
59 This driver can be used as a way to compare di 55 This driver can be used as a way to compare different userspace implementations.
60 This assumes that a working client is run agai 56 This assumes that a working client is run against visl and that the ftrace and
61 OUTPUT buffer data is subsequently used to deb 57 OUTPUT buffer data is subsequently used to debug a work-in-progress
62 implementation. 58 implementation.
63 59
64 Even though no video decoding is actually done !! 60 Information on reference frames, their timestamps, the status of the OUTPUT and
65 against a reference for a given input, except !! 61 CAPTURE queues and more can be read directly from the CAPTURE buffers.
66 <<
67 Depending on the tpg_verbose parameter value, <<
68 their timestamps, the status of the OUTPUT and <<
69 read directly from the CAPTURE buffers. <<
70 62
71 Supported codecs 63 Supported codecs
72 ---------------- 64 ----------------
73 65
74 The following codecs are supported: 66 The following codecs are supported:
75 67
76 - FWHT 68 - FWHT
77 - MPEG2 69 - MPEG2
78 - VP8 70 - VP8
79 - VP9 71 - VP9
80 - H.264 72 - H.264
81 - HEVC 73 - HEVC
82 - AV1 74 - AV1
83 75
84 visl trace events 76 visl trace events
85 ----------------- 77 -----------------
86 The trace events are defined on a per-codec ba 78 The trace events are defined on a per-codec basis, e.g.:
87 79
88 .. code-block:: bash 80 .. code-block:: bash
89 81
90 $ ls /sys/kernel/tracing/events/ | gre 82 $ ls /sys/kernel/tracing/events/ | grep visl
91 visl_av1_controls 83 visl_av1_controls
92 visl_fwht_controls 84 visl_fwht_controls
93 visl_h264_controls 85 visl_h264_controls
94 visl_hevc_controls 86 visl_hevc_controls
95 visl_mpeg2_controls 87 visl_mpeg2_controls
96 visl_vp8_controls 88 visl_vp8_controls
97 visl_vp9_controls 89 visl_vp9_controls
98 90
99 For example, in order to dump HEVC SPS data: 91 For example, in order to dump HEVC SPS data:
100 92
101 .. code-block:: bash 93 .. code-block:: bash
102 94
103 $ echo 1 > /sys/kernel/tracing/events 95 $ echo 1 > /sys/kernel/tracing/events/visl_hevc_controls/v4l2_ctrl_hevc_sps/enable
104 96
105 The SPS data will be dumped to the trace buffe 97 The SPS data will be dumped to the trace buffer, i.e.:
106 98
107 .. code-block:: bash 99 .. code-block:: bash
108 100
109 $ cat /sys/kernel/tracing/trace 101 $ cat /sys/kernel/tracing/trace
110 video_parameter_set_id 0 102 video_parameter_set_id 0
111 seq_parameter_set_id 0 103 seq_parameter_set_id 0
112 pic_width_in_luma_samples 1920 104 pic_width_in_luma_samples 1920
113 pic_height_in_luma_samples 1080 105 pic_height_in_luma_samples 1080
114 bit_depth_luma_minus8 0 106 bit_depth_luma_minus8 0
115 bit_depth_chroma_minus8 0 107 bit_depth_chroma_minus8 0
116 log2_max_pic_order_cnt_lsb_minus4 4 108 log2_max_pic_order_cnt_lsb_minus4 4
117 sps_max_dec_pic_buffering_minus1 6 109 sps_max_dec_pic_buffering_minus1 6
118 sps_max_num_reorder_pics 2 110 sps_max_num_reorder_pics 2
119 sps_max_latency_increase_plus1 0 111 sps_max_latency_increase_plus1 0
120 log2_min_luma_coding_block_size_minus3 112 log2_min_luma_coding_block_size_minus3 0
121 log2_diff_max_min_luma_coding_block_si 113 log2_diff_max_min_luma_coding_block_size 3
122 log2_min_luma_transform_block_size_min 114 log2_min_luma_transform_block_size_minus2 0
123 log2_diff_max_min_luma_transform_block 115 log2_diff_max_min_luma_transform_block_size 3
124 max_transform_hierarchy_depth_inter 2 116 max_transform_hierarchy_depth_inter 2
125 max_transform_hierarchy_depth_intra 2 117 max_transform_hierarchy_depth_intra 2
126 pcm_sample_bit_depth_luma_minus1 0 118 pcm_sample_bit_depth_luma_minus1 0
127 pcm_sample_bit_depth_chroma_minus1 0 119 pcm_sample_bit_depth_chroma_minus1 0
128 log2_min_pcm_luma_coding_block_size_mi 120 log2_min_pcm_luma_coding_block_size_minus3 0
129 log2_diff_max_min_pcm_luma_coding_bloc 121 log2_diff_max_min_pcm_luma_coding_block_size 0
130 num_short_term_ref_pic_sets 0 122 num_short_term_ref_pic_sets 0
131 num_long_term_ref_pics_sps 0 123 num_long_term_ref_pics_sps 0
132 chroma_format_idc 1 124 chroma_format_idc 1
133 sps_max_sub_layers_minus1 0 125 sps_max_sub_layers_minus1 0
134 flags AMP_ENABLED|SAMPLE_ADAPTIVE_OFFS 126 flags AMP_ENABLED|SAMPLE_ADAPTIVE_OFFSET|TEMPORAL_MVP_ENABLED|STRONG_INTRA_SMOOTHING_ENABLED
135 127
136 128
137 Dumping OUTPUT buffer data through debugfs 129 Dumping OUTPUT buffer data through debugfs
138 ------------------------------------------ 130 ------------------------------------------
139 131
140 If the **VISL_DEBUGFS** Kconfig is enabled, vi 132 If the **VISL_DEBUGFS** Kconfig is enabled, visl will populate
141 **/sys/kernel/debug/visl/bitstream** with OUTP 133 **/sys/kernel/debug/visl/bitstream** with OUTPUT buffer data according to the
142 values of bitstream_trace_frame_start and bits 134 values of bitstream_trace_frame_start and bitstream_trace_nframes. This can
143 highlight errors as broken clients may fail to 135 highlight errors as broken clients may fail to fill the buffers properly.
144 136
145 A single file is created for each processed OU 137 A single file is created for each processed OUTPUT buffer. Its name contains an
146 integer that denotes the buffer sequence, i.e. 138 integer that denotes the buffer sequence, i.e.:
147 139
148 .. code-block:: c 140 .. code-block:: c
149 141
150 snprintf(name, 32, "bitstream%d", run- 142 snprintf(name, 32, "bitstream%d", run->src->sequence);
151 143
152 Dumping the values is simply a matter of readi 144 Dumping the values is simply a matter of reading from the file, i.e.:
153 145
154 For the buffer with sequence == 0: 146 For the buffer with sequence == 0:
155 147
156 .. code-block:: bash 148 .. code-block:: bash
157 149
158 $ xxd /sys/kernel/debug/visl/bitstream 150 $ xxd /sys/kernel/debug/visl/bitstream/bitstream0
159 00000000: 2601 af04 d088 bc25 a173 0e4 151 00000000: 2601 af04 d088 bc25 a173 0e41 a4f2 3274 &......%.s.A..2t
160 00000010: c668 cb28 e775 b4ac f53a ba6 152 00000010: c668 cb28 e775 b4ac f53a ba60 f8fd 3aa1 .h.(.u...:.`..:.
161 00000020: 46b4 bcfc 506c e227 2372 e5f 153 00000020: 46b4 bcfc 506c e227 2372 e5f5 d7ea 579f F...Pl.'#r....W.
162 00000030: 6371 5eb5 0eb8 23b5 ca6a 5de 154 00000030: 6371 5eb5 0eb8 23b5 ca6a 5de5 983a 19e4 cq^...#..j]..:..
163 00000040: e8c3 4320 b4ba a226 cbc1 413 155 00000040: e8c3 4320 b4ba a226 cbc1 4138 3a12 32d6 ..C ...&..A8:.2.
164 00000050: fef3 247b 3523 4e90 9682 ac8 156 00000050: fef3 247b 3523 4e90 9682 ac8e eb0c a389 ..${5#N.........
165 00000060: ddd0 6cfc 0187 0e20 7aae b15 157 00000060: ddd0 6cfc 0187 0e20 7aae b15b 1812 3d33 ..l.... z..[..=3
166 00000070: e1c5 f425 a83a 00b7 4f18 812 158 00000070: e1c5 f425 a83a 00b7 4f18 8127 3c4c aefb ...%.:..O..'<L..
167 159
168 For the buffer with sequence == 1: 160 For the buffer with sequence == 1:
169 161
170 .. code-block:: bash 162 .. code-block:: bash
171 163
172 $ xxd /sys/kernel/debug/visl/bitstream 164 $ xxd /sys/kernel/debug/visl/bitstream/bitstream1
173 00000000: 0201 d021 49e1 0c40 aa11 144 165 00000000: 0201 d021 49e1 0c40 aa11 1449 14a6 01dc ...!I..@...I....
174 00000010: 7023 889a c8cd 2cd0 13b4 dab 166 00000010: 7023 889a c8cd 2cd0 13b4 dab0 e8ca 21fe p#....,.......!.
175 00000020: c4c8 ab4c 486e 4e2f b0df 96c 167 00000020: c4c8 ab4c 486e 4e2f b0df 96cc c74e 8dde ...LHnN/.....N..
176 00000030: 8ce7 ee36 d880 4095 4d64 30a 168 00000030: 8ce7 ee36 d880 4095 4d64 30a0 ff4f 0c5e ...6..@.Md0..O.^
177 00000040: f16b a6a1 d806 ca2a 0ece a67 169 00000040: f16b a6a1 d806 ca2a 0ece a673 7bea 1f37 .k.....*...s{..7
178 00000050: 370f 5bb9 1dc4 ba21 6434 bc5 170 00000050: 370f 5bb9 1dc4 ba21 6434 bc53 0173 cba0 7.[....!d4.S.s..
179 00000060: dfe6 bc99 01ea b6e0 346b 92b 171 00000060: dfe6 bc99 01ea b6e0 346b 92b5 c8de 9f5d ........4k.....]
180 00000070: e7cc 3484 1769 fef2 a693 a94 172 00000070: e7cc 3484 1769 fef2 a693 a945 2c8b 31da ..4..i.....E,.1.
181 173
182 And so on. 174 And so on.
183 175
184 By default, the files are removed during STREA 176 By default, the files are removed during STREAMOFF. This is to reduce the amount
185 of clutter. 177 of clutter.
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