blob: 3820f58d69e253eea3db7a1a4bf83915f8e9c7dc
1 | /* |
2 | * copyright (c) 2008 Paul Kendall <paul@kcbbs.gen.nz> |
3 | * |
4 | * This file is part of FFmpeg. |
5 | * |
6 | * FFmpeg is free software; you can redistribute it and/or |
7 | * modify it under the terms of the GNU Lesser General Public |
8 | * License as published by the Free Software Foundation; either |
9 | * version 2.1 of the License, or (at your option) any later version. |
10 | * |
11 | * FFmpeg is distributed in the hope that it will be useful, |
12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
14 | * Lesser General Public License for more details. |
15 | * |
16 | * You should have received a copy of the GNU Lesser General Public |
17 | * License along with FFmpeg; if not, write to the Free Software |
18 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
19 | */ |
20 | |
21 | /** |
22 | * @file |
23 | * AAC LATM parser |
24 | */ |
25 | |
26 | #include <stdint.h> |
27 | #include "parser.h" |
28 | |
29 | #define LATM_HEADER 0x56e000 // 0x2b7 (11 bits) |
30 | #define LATM_MASK 0xFFE000 // top 11 bits |
31 | #define LATM_SIZE_MASK 0x001FFF // bottom 13 bits |
32 | |
33 | typedef struct LATMParseContext{ |
34 | ParseContext pc; |
35 | int count; |
36 | } LATMParseContext; |
37 | |
38 | /** |
39 | * Find the end of the current frame in the bitstream. |
40 | * @return the position of the first byte of the next frame, or -1 |
41 | */ |
42 | static int latm_find_frame_end(AVCodecParserContext *s1, const uint8_t *buf, |
43 | int buf_size) |
44 | { |
45 | LATMParseContext *s = s1->priv_data; |
46 | ParseContext *pc = &s->pc; |
47 | int pic_found, i; |
48 | uint32_t state; |
49 | |
50 | pic_found = pc->frame_start_found; |
51 | state = pc->state; |
52 | |
53 | if (!pic_found) { |
54 | for (i = 0; i < buf_size; i++) { |
55 | state = (state<<8) | buf[i]; |
56 | if ((state & LATM_MASK) == LATM_HEADER) { |
57 | i++; |
58 | s->count = -i; |
59 | pic_found = 1; |
60 | break; |
61 | } |
62 | } |
63 | } |
64 | |
65 | if (pic_found) { |
66 | /* EOF considered as end of frame */ |
67 | if (buf_size == 0) |
68 | return 0; |
69 | if ((state & LATM_SIZE_MASK) - s->count <= buf_size) { |
70 | pc->frame_start_found = 0; |
71 | pc->state = -1; |
72 | return (state & LATM_SIZE_MASK) - s->count; |
73 | } |
74 | } |
75 | |
76 | s->count += buf_size; |
77 | pc->frame_start_found = pic_found; |
78 | pc->state = state; |
79 | |
80 | return END_NOT_FOUND; |
81 | } |
82 | |
83 | static int latm_parse(AVCodecParserContext *s1, AVCodecContext *avctx, |
84 | const uint8_t **poutbuf, int *poutbuf_size, |
85 | const uint8_t *buf, int buf_size) |
86 | { |
87 | LATMParseContext *s = s1->priv_data; |
88 | ParseContext *pc = &s->pc; |
89 | int next; |
90 | |
91 | if (s1->flags & PARSER_FLAG_COMPLETE_FRAMES) { |
92 | next = buf_size; |
93 | } else { |
94 | next = latm_find_frame_end(s1, buf, buf_size); |
95 | |
96 | if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) { |
97 | *poutbuf = NULL; |
98 | *poutbuf_size = 0; |
99 | return buf_size; |
100 | } |
101 | } |
102 | *poutbuf = buf; |
103 | *poutbuf_size = buf_size; |
104 | return next; |
105 | } |
106 | |
107 | AVCodecParser ff_aac_latm_parser = { |
108 | .codec_ids = { AV_CODEC_ID_AAC_LATM }, |
109 | .priv_data_size = sizeof(LATMParseContext), |
110 | .parser_parse = latm_parse, |
111 | .parser_close = ff_parse_close |
112 | }; |
113 |