1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * Coda multi-standard codec IP - MPEG-2 helper functions
4  *
5  * Copyright (C) 2019 Pengutronix, Philipp Zabel
6  */
7 
8 #include <linux/kernel.h>
9 #include <linux/videodev2.h>
10 #include "coda.h"
11 
12 int coda_mpeg2_profile(int profile_idc)
13 {
14 	switch (profile_idc) {
15 	case 5:
16 		return V4L2_MPEG_VIDEO_MPEG2_PROFILE_SIMPLE;
17 	case 4:
18 		return V4L2_MPEG_VIDEO_MPEG2_PROFILE_MAIN;
19 	case 3:
20 		return V4L2_MPEG_VIDEO_MPEG2_PROFILE_SNR_SCALABLE;
21 	case 2:
22 		return V4L2_MPEG_VIDEO_MPEG2_PROFILE_SPATIALLY_SCALABLE;
23 	case 1:
24 		return V4L2_MPEG_VIDEO_MPEG2_PROFILE_HIGH;
25 	default:
26 		return -EINVAL;
27 	}
28 }
29 
30 int coda_mpeg2_level(int level_idc)
31 {
32 	switch (level_idc) {
33 	case 10:
34 		return V4L2_MPEG_VIDEO_MPEG2_LEVEL_LOW;
35 	case 8:
36 		return V4L2_MPEG_VIDEO_MPEG2_LEVEL_MAIN;
37 	case 6:
38 		return V4L2_MPEG_VIDEO_MPEG2_LEVEL_HIGH_1440;
39 	case 4:
40 		return V4L2_MPEG_VIDEO_MPEG2_LEVEL_HIGH;
41 	default:
42 		return -EINVAL;
43 	}
44 }
45 
46 /*
47  * Check if the buffer starts with the MPEG-2 sequence header (with or without
48  * quantization matrix) and extension header, for example:
49  *
50  *   00 00 01 b3 2d 01 e0 34 08 8b a3 81
51  *               10 11 11 12 12 12 13 13 13 13 14 14 14 14 14 15
52  *               15 15 15 15 15 16 16 16 16 16 16 16 17 17 17 17
53  *               17 17 17 17 18 18 18 19 18 18 18 19 1a 1a 1a 1a
54  *               19 1b 1b 1b 1b 1b 1c 1c 1c 1c 1e 1e 1e 1f 1f 21
55  *   00 00 01 b5 14 8a 00 01 00 00
56  *
57  * or:
58  *
59  *   00 00 01 b3 08 00 40 15 ff ff e0 28
60  *   00 00 01 b5 14 8a 00 01 00 00
61  *
62  * Returns the detected header size in bytes or 0.
63  */
64 u32 coda_mpeg2_parse_headers(struct coda_ctx *ctx, u8 *buf, u32 size)
65 {
66 	static const u8 sequence_header_start[4] = { 0x00, 0x00, 0x01, 0xb3 };
67 	static const union {
68 		u8 extension_start[4];
69 		u8 start_code_prefix[3];
70 	} u = { { 0x00, 0x00, 0x01, 0xb5 } };
71 
72 	if (size < 22 ||
73 	    memcmp(buf, sequence_header_start, 4) != 0)
74 		return 0;
75 
76 	if ((size == 22 ||
77 	     (size >= 25 && memcmp(buf + 22, u.start_code_prefix, 3) == 0)) &&
78 	    memcmp(buf + 12, u.extension_start, 4) == 0)
79 		return 22;
80 
81 	if ((size == 86 ||
82 	     (size > 89 && memcmp(buf + 86, u.start_code_prefix, 3) == 0)) &&
83 	    memcmp(buf + 76, u.extension_start, 4) == 0)
84 		return 86;
85 
86 	return 0;
87 }
88