libavcodec/amr_parser.c

   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
  28 #include "libavutil/channel_layout.h"
  29 #include "libavutil/intreadwrite.h"
  30 #include "parser.h"
  31 #include "parser_internal.h"
  32
  33 static const uint8_t amrnb_packed_size[16] = {
  34     13, 14, 16, 18, 20, 21, 27, 32, 6, 1, 1, 1, 1, 1, 1, 1
  35 };
  36 static const uint8_t amrwb_packed_size[16] = {
  37     18, 24, 33, 37, 41, 47, 51, 59, 61, 6, 1, 1, 1, 1, 1, 1
  38 };
  39
  40 typedef struct AMRParseContext {
  41     ParseContext pc;
  42     uint64_t cumulated_size;
  43     uint64_t block_count;
  44     int current_channel;
  45     int remaining;
  46 } AMRParseContext;
  47
  48 static av_cold int amr_parse_init(AVCodecParserContext *s1)
  49 {
  50     AMRParseContext *s = s1->priv_data;
  51     s->remaining = -1;
  52     return 0;
  53 }
  54
  55 static int amr_parse(AVCodecParserContext *s1,
  56                      AVCodecContext *avctx,
  57                      const uint8_t **poutbuf, int *poutbuf_size,
  58                      const uint8_t *buf, int buf_size)
  59 {
  60     AMRParseContext *s = s1->priv_data;
  61     ParseContext *pc = &s->pc;
  62     int next = END_NOT_FOUND;
  63
  64     *poutbuf_size = 0;
  65     *poutbuf = NULL;
  66
  67     if (!avctx->ch_layout.nb_channels) {
  68         av_channel_layout_uninit(&avctx->ch_layout);
  69         avctx->ch_layout      = (AVChannelLayout)AV_CHANNEL_LAYOUT_MONO;
  70     }
  71
  72     if (s1->flags & PARSER_FLAG_COMPLETE_FRAMES) {
  73         next = buf_size;
  74     } else {
  75         int ch, offset = 0;
  76
  77         for (ch = s->current_channel; ch < avctx->ch_layout.nb_channels; ch++) {
  78             if (s->remaining >= 0) {
  79                 next = s->remaining;
  80             } else {
  81                 int mode = (buf[offset] >> 3) & 0x0F;
  82
  83                 if (avctx->codec_id == AV_CODEC_ID_AMR_NB) {
  84                     next = amrnb_packed_size[mode];
  85                 } else if (avctx->codec_id == AV_CODEC_ID_AMR_WB) {
  86                     next = amrwb_packed_size[mode];
  87                 }
  88             }
  89
  90             offset += next;
  91             if (offset >= buf_size) {
  92                 s->remaining = offset - buf_size;
  93                 next = END_NOT_FOUND;
  94                 break;
  95             } else {
  96                 s->remaining = -1;
  97             }
  98         }
  99
 100         s->current_channel = ch % avctx->ch_layout.nb_channels;
 101         if (s->remaining < 0)
 102             next = offset;
 103
 104         if (next != END_NOT_FOUND) {
 105             if (s->cumulated_size < UINT64_MAX - next) {
 106                 s->cumulated_size += next;
 107                 /* Both AMR formats have 50 frames per second */
 108                 avctx->bit_rate = s->cumulated_size / ++s->block_count * 8 * 50;
 109             }
 110         }
 111
 112         if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
 113             *poutbuf      = NULL;
 114             *poutbuf_size = 0;
 115             return buf_size;
 116         }
 117     }
 118
 119     s1->duration = avctx->codec_id == AV_CODEC_ID_AMR_NB ? 160 : 320;
 120
 121     *poutbuf = buf;
 122     *poutbuf_size = buf_size;
 123     return next;
 124 }
 125
 126 const FFCodecParser ff_amr_parser = {
 127     PARSER_CODEC_LIST(AV_CODEC_ID_AMR_NB, AV_CODEC_ID_AMR_WB),
 128     .priv_data_size = sizeof(AMRParseContext),
 129     .init           = amr_parse_init,
 130     .parse          = amr_parse,
 131     .close          = ff_parse_close,
 132 };