1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  *  TW5864 driver - H.264 headers generation functions
4  *
5  *  Copyright (C) 2016 Bluecherry, LLC <maintainers@bluecherrydvr.com>
6  */
7 
8 #include <linux/log2.h>
9 
10 #include "tw5864.h"
11 
12 static u8 marker[] = { 0x00, 0x00, 0x00, 0x01 };
13 
14 /*
15  * Exponential-Golomb coding functions
16  *
17  * These functions are used for generation of H.264 bitstream headers.
18  *
19  * This code is derived from tw5864 reference driver by manufacturers, which
20  * itself apparently was derived from x264 project.
21  */
22 
23 /* Bitstream writing context */
24 struct bs {
25 	u8 *buf; /* pointer to buffer beginning */
26 	u8 *buf_end; /* pointer to buffer end */
27 	u8 *ptr; /* pointer to current byte in buffer */
28 	unsigned int bits_left; /* number of available bits in current byte */
29 };
30 
31 static void bs_init(struct bs *s, void *buf, int size)
32 {
33 	s->buf = buf;
34 	s->ptr = buf;
35 	s->buf_end = s->ptr + size;
36 	s->bits_left = 8;
37 }
38 
39 static int bs_len(struct bs *s)
40 {
41 	return s->ptr - s->buf;
42 }
43 
44 static void bs_write(struct bs *s, int count, u32 bits)
45 {
46 	if (s->ptr >= s->buf_end - 4)
47 		return;
48 	while (count > 0) {
49 		if (count < 32)
50 			bits &= (1 << count) - 1;
51 		if (count < s->bits_left) {
52 			*s->ptr = (*s->ptr << count) | bits;
53 			s->bits_left -= count;
54 			break;
55 		}
56 		*s->ptr = (*s->ptr << s->bits_left) |
57 			(bits >> (count - s->bits_left));
58 		count -= s->bits_left;
59 		s->ptr++;
60 		s->bits_left = 8;
61 	}
62 }
63 
64 static void bs_write1(struct bs *s, u32 bit)
65 {
66 	if (s->ptr < s->buf_end) {
67 		*s->ptr <<= 1;
68 		*s->ptr |= bit;
69 		s->bits_left--;
70 		if (s->bits_left == 0) {
71 			s->ptr++;
72 			s->bits_left = 8;
73 		}
74 	}
75 }
76 
77 static void bs_write_ue(struct bs *s, u32 val)
78 {
79 	if (val == 0) {
80 		bs_write1(s, 1);
81 	} else {
82 		val++;
83 		bs_write(s, 2 * fls(val) - 1, val);
84 	}
85 }
86 
87 static void bs_write_se(struct bs *s, int val)
88 {
89 	bs_write_ue(s, val <= 0 ? -val * 2 : val * 2 - 1);
90 }
91 
92 static void bs_rbsp_trailing(struct bs *s)
93 {
94 	bs_write1(s, 1);
95 	if (s->bits_left != 8)
96 		bs_write(s, s->bits_left, 0x00);
97 }
98 
99 /* H.264 headers generation functions */
100 
101 static int tw5864_h264_gen_sps_rbsp(u8 *buf, size_t size, int width, int height)
102 {
103 	struct bs bs, *s;
104 
105 	s = &bs;
106 	bs_init(s, buf, size);
107 	bs_write(s, 8, 0x42); /* profile_idc, baseline */
108 	bs_write(s, 1, 1); /* constraint_set0_flag */
109 	bs_write(s, 1, 1); /* constraint_set1_flag */
110 	bs_write(s, 1, 0); /* constraint_set2_flag */
111 	bs_write(s, 5, 0); /* reserved_zero_5bits */
112 	bs_write(s, 8, 0x1e); /* level_idc */
113 	bs_write_ue(s, 0); /* seq_parameter_set_id */
114 	bs_write_ue(s, ilog2(MAX_GOP_SIZE) - 4); /* log2_max_frame_num_minus4 */
115 	bs_write_ue(s, 0); /* pic_order_cnt_type */
116 	/* log2_max_pic_order_cnt_lsb_minus4 */
117 	bs_write_ue(s, ilog2(MAX_GOP_SIZE) - 4);
118 	bs_write_ue(s, 1); /* num_ref_frames */
119 	bs_write(s, 1, 0); /* gaps_in_frame_num_value_allowed_flag */
120 	bs_write_ue(s, width / 16 - 1); /* pic_width_in_mbs_minus1 */
121 	bs_write_ue(s, height / 16 - 1); /* pic_height_in_map_units_minus1 */
122 	bs_write(s, 1, 1); /* frame_mbs_only_flag */
123 	bs_write(s, 1, 0); /* direct_8x8_inference_flag */
124 	bs_write(s, 1, 0); /* frame_cropping_flag */
125 	bs_write(s, 1, 0); /* vui_parameters_present_flag */
126 	bs_rbsp_trailing(s);
127 	return bs_len(s);
128 }
129 
130 static int tw5864_h264_gen_pps_rbsp(u8 *buf, size_t size, int qp)
131 {
132 	struct bs bs, *s;
133 
134 	s = &bs;
135 	bs_init(s, buf, size);
136 	bs_write_ue(s, 0); /* pic_parameter_set_id */
137 	bs_write_ue(s, 0); /* seq_parameter_set_id */
138 	bs_write(s, 1, 0); /* entropy_coding_mode_flag */
139 	bs_write(s, 1, 0); /* pic_order_present_flag */
140 	bs_write_ue(s, 0); /* num_slice_groups_minus1 */
141 	bs_write_ue(s, 0); /* i_num_ref_idx_l0_active_minus1 */
142 	bs_write_ue(s, 0); /* i_num_ref_idx_l1_active_minus1 */
143 	bs_write(s, 1, 0); /* weighted_pred_flag */
144 	bs_write(s, 2, 0); /* weighted_bipred_idc */
145 	bs_write_se(s, qp - 26); /* pic_init_qp_minus26 */
146 	bs_write_se(s, qp - 26); /* pic_init_qs_minus26 */
147 	bs_write_se(s, 0); /* chroma_qp_index_offset */
148 	bs_write(s, 1, 0); /* deblocking_filter_control_present_flag */
149 	bs_write(s, 1, 0); /* constrained_intra_pred_flag */
150 	bs_write(s, 1, 0); /* redundant_pic_cnt_present_flag */
151 	bs_rbsp_trailing(s);
152 	return bs_len(s);
153 }
154 
155 static int tw5864_h264_gen_slice_head(u8 *buf, size_t size,
156 				      unsigned int idr_pic_id,
157 				      unsigned int frame_gop_seqno,
158 				      int *tail_nb_bits, u8 *tail)
159 {
160 	struct bs bs, *s;
161 	int is_i_frame = frame_gop_seqno == 0;
162 
163 	s = &bs;
164 	bs_init(s, buf, size);
165 	bs_write_ue(s, 0); /* first_mb_in_slice */
166 	bs_write_ue(s, is_i_frame ? 2 : 5); /* slice_type - I or P */
167 	bs_write_ue(s, 0); /* pic_parameter_set_id */
168 	bs_write(s, ilog2(MAX_GOP_SIZE), frame_gop_seqno); /* frame_num */
169 	if (is_i_frame)
170 		bs_write_ue(s, idr_pic_id);
171 
172 	/* pic_order_cnt_lsb */
173 	bs_write(s, ilog2(MAX_GOP_SIZE), frame_gop_seqno);
174 
175 	if (is_i_frame) {
176 		bs_write1(s, 0); /* no_output_of_prior_pics_flag */
177 		bs_write1(s, 0); /* long_term_reference_flag */
178 	} else {
179 		bs_write1(s, 0); /* num_ref_idx_active_override_flag */
180 		bs_write1(s, 0); /* ref_pic_list_reordering_flag_l0 */
181 		bs_write1(s, 0); /* adaptive_ref_pic_marking_mode_flag */
182 	}
183 
184 	bs_write_se(s, 0); /* slice_qp_delta */
185 
186 	if (s->bits_left != 8) {
187 		*tail = ((s->ptr[0]) << s->bits_left);
188 		*tail_nb_bits = 8 - s->bits_left;
189 	} else {
190 		*tail = 0;
191 		*tail_nb_bits = 0;
192 	}
193 
194 	return bs_len(s);
195 }
196 
197 void tw5864_h264_put_stream_header(u8 **buf, size_t *space_left, int qp,
198 				   int width, int height)
199 {
200 	int nal_len;
201 
202 	/* SPS */
203 	memcpy(*buf, marker, sizeof(marker));
204 	*buf += 4;
205 	*space_left -= 4;
206 
207 	**buf = 0x67; /* SPS NAL header */
208 	*buf += 1;
209 	*space_left -= 1;
210 
211 	nal_len = tw5864_h264_gen_sps_rbsp(*buf, *space_left, width, height);
212 	*buf += nal_len;
213 	*space_left -= nal_len;
214 
215 	/* PPS */
216 	memcpy(*buf, marker, sizeof(marker));
217 	*buf += 4;
218 	*space_left -= 4;
219 
220 	**buf = 0x68; /* PPS NAL header */
221 	*buf += 1;
222 	*space_left -= 1;
223 
224 	nal_len = tw5864_h264_gen_pps_rbsp(*buf, *space_left, qp);
225 	*buf += nal_len;
226 	*space_left -= nal_len;
227 }
228 
229 void tw5864_h264_put_slice_header(u8 **buf, size_t *space_left,
230 				  unsigned int idr_pic_id,
231 				  unsigned int frame_gop_seqno,
232 				  int *tail_nb_bits, u8 *tail)
233 {
234 	int nal_len;
235 
236 	memcpy(*buf, marker, sizeof(marker));
237 	*buf += 4;
238 	*space_left -= 4;
239 
240 	/* Frame NAL header */
241 	**buf = (frame_gop_seqno == 0) ? 0x25 : 0x21;
242 	*buf += 1;
243 	*space_left -= 1;
244 
245 	nal_len = tw5864_h264_gen_slice_head(*buf, *space_left, idr_pic_id,
246 					     frame_gop_seqno, tail_nb_bits,
247 					     tail);
248 	*buf += nal_len;
249 	*space_left -= nal_len;
250 }
251