FFmpeg
amr_parser.c
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1 /*
2  * Copyright (c) 2021 Paul B Mahol
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  * AMR audio parser
24  *
25  * Splits packets into individual blocks.
26  */
27 
29 #include "libavutil/intreadwrite.h"
30 #include "parser.h"
31 
32 static const uint8_t amrnb_packed_size[16] = {
33  13, 14, 16, 18, 20, 21, 27, 32, 6, 1, 1, 1, 1, 1, 1, 1
34 };
35 static const uint8_t amrwb_packed_size[16] = {
36  18, 24, 33, 37, 41, 47, 51, 59, 61, 6, 1, 1, 1, 1, 1, 1
37 };
38 
39 typedef struct AMRParseContext {
41  uint64_t cumulated_size;
42  uint64_t block_count;
44  int remaining;
46 
48 {
49  AMRParseContext *s = s1->priv_data;
50  s->remaining = -1;
51  return 0;
52 }
53 
55  AVCodecContext *avctx,
56  const uint8_t **poutbuf, int *poutbuf_size,
57  const uint8_t *buf, int buf_size)
58 {
59  AMRParseContext *s = s1->priv_data;
60  ParseContext *pc = &s->pc;
61  int next = END_NOT_FOUND;
62 
63  *poutbuf_size = 0;
64  *poutbuf = NULL;
65 
66  if (!avctx->ch_layout.nb_channels) {
69  }
70 
71  if (s1->flags & PARSER_FLAG_COMPLETE_FRAMES) {
72  next = buf_size;
73  } else {
74  int ch, offset = 0;
75 
76  for (ch = s->current_channel; ch < avctx->ch_layout.nb_channels; ch++) {
77  if (s->remaining >= 0) {
78  next = s->remaining;
79  } else {
80  int mode = (buf[offset] >> 3) & 0x0F;
81 
82  if (avctx->codec_id == AV_CODEC_ID_AMR_NB) {
83  next = amrnb_packed_size[mode];
84  } else if (avctx->codec_id == AV_CODEC_ID_AMR_WB) {
85  next = amrwb_packed_size[mode];
86  }
87  }
88 
89  offset += next;
90  if (offset >= buf_size) {
91  s->remaining = offset - buf_size;
92  next = END_NOT_FOUND;
93  break;
94  } else {
95  s->remaining = -1;
96  }
97  }
98 
99  s->current_channel = ch % avctx->ch_layout.nb_channels;
100  if (s->remaining < 0)
101  next = offset;
102 
103  if (next != END_NOT_FOUND) {
104  if (s->cumulated_size < UINT64_MAX - next) {
105  s->cumulated_size += next;
106  /* Both AMR formats have 50 frames per second */
107  avctx->bit_rate = s->cumulated_size / ++s->block_count * 8 * 50;
108  }
109  }
110 
111  if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
112  *poutbuf = NULL;
113  *poutbuf_size = 0;
114  return buf_size;
115  }
116  }
117 
118  s1->duration = avctx->codec_id == AV_CODEC_ID_AMR_NB ? 160 : 320;
119 
120  *poutbuf = buf;
121  *poutbuf_size = buf_size;
122  return next;
123 }
124 
127  .priv_data_size = sizeof(AMRParseContext),
128  .parser_init = amr_parse_init,
129  .parser_parse = amr_parse,
130  .parser_close = ff_parse_close,
131 };
AMRParseContext::cumulated_size
uint64_t cumulated_size
Definition: amr_parser.c:41
ff_parse_close
void ff_parse_close(AVCodecParserContext *s)
Definition: parser.c:284
amr_parse_init
static av_cold int amr_parse_init(AVCodecParserContext *s1)
Definition: amr_parser.c:47
AV_CHANNEL_LAYOUT_MONO
#define AV_CHANNEL_LAYOUT_MONO
Definition: channel_layout.h:353
AV_CODEC_ID_AMR_NB
@ AV_CODEC_ID_AMR_NB
Definition: codec_id.h:408
AVChannelLayout::nb_channels
int nb_channels
Number of channels in this layout.
Definition: channel_layout.h:300
AV_CODEC_ID_AMR_WB
@ AV_CODEC_ID_AMR_WB
Definition: codec_id.h:409
ParseContext
Definition: parser.h:28
AVCodecContext::ch_layout
AVChannelLayout ch_layout
Audio channel layout.
Definition: avcodec.h:2057
av_cold
#define av_cold
Definition: attributes.h:90
intreadwrite.h
s
#define s(width, name)
Definition: cbs_vp9.c:256
AMRParseContext
Definition: amr_parser.c:39
s1
#define s1
Definition: regdef.h:38
AVCodecContext::codec_id
enum AVCodecID codec_id
Definition: avcodec.h:399
NULL
#define NULL
Definition: coverity.c:32
AMRParseContext::pc
ParseContext pc
Definition: amr_parser.c:40
AVCodecContext::bit_rate
int64_t bit_rate
the average bitrate
Definition: avcodec.h:439
av_channel_layout_uninit
void av_channel_layout_uninit(AVChannelLayout *channel_layout)
Free any allocated data in the channel layout and reset the channel count to 0.
Definition: channel_layout.c:630
amr_parse
static int amr_parse(AVCodecParserContext *s1, AVCodecContext *avctx, const uint8_t **poutbuf, int *poutbuf_size, const uint8_t *buf, int buf_size)
Definition: amr_parser.c:54
AVCodecParser::codec_ids
int codec_ids[7]
Definition: avcodec.h:2950
AVChannelLayout
An AVChannelLayout holds information about the channel layout of audio data.
Definition: channel_layout.h:290
offset
it s the only field you need to keep assuming you have a context There is some magic you don t need to care about around this just let it vf offset
Definition: writing_filters.txt:86
ff_combine_frame
int ff_combine_frame(ParseContext *pc, int next, const uint8_t **buf, int *buf_size)
Combine the (truncated) bitstream to a complete frame.
Definition: parser.c:199
ff_amr_parser
const AVCodecParser ff_amr_parser
Definition: amr_parser.c:125
PARSER_FLAG_COMPLETE_FRAMES
#define PARSER_FLAG_COMPLETE_FRAMES
Definition: avcodec.h:2824
AMRParseContext::remaining
int remaining
Definition: amr_parser.c:44
parser.h
AVCodecParserContext
Definition: avcodec.h:2790
AVCodecContext
main external API structure.
Definition: avcodec.h:389
amrwb_packed_size
static const uint8_t amrwb_packed_size[16]
Definition: amr_parser.c:35
channel_layout.h
mode
mode
Definition: ebur128.h:83
AMRParseContext::block_count
uint64_t block_count
Definition: amr_parser.c:42
AMRParseContext::current_channel
int current_channel
Definition: amr_parser.c:43
END_NOT_FOUND
#define END_NOT_FOUND
Definition: parser.h:40
AVCodecParser
Definition: avcodec.h:2949
amrnb_packed_size
static const uint8_t amrnb_packed_size[16]
Definition: amr_parser.c:32