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
  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 {
  40     ParseContext pc;
  41     uint64_t cumulated_size;
  42     uint64_t block_count;
  43     int current_channel;
  44     int remaining;
  45 } AMRParseContext;
  46
  47 static av_cold int amr_parse_init(AVCodecParserContext *s1)
  48 {
  49     AMRParseContext *s = s1->priv_data;
  50     s->remaining = -1;
  51     return 0;
  52 }
  53
  54 static int amr_parse(AVCodecParserContext *s1,
  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) {
  67         av_channel_layout_uninit(&avctx->ch_layout);
  68         avctx->ch_layout      = (AVChannelLayout)AV_CHANNEL_LAYOUT_MONO;
  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
 125 const AVCodecParser ff_amr_parser = {
 126     .codec_ids      = { AV_CODEC_ID_AMR_NB, AV_CODEC_ID_AMR_WB },
 127     .priv_data_size = sizeof(AMRParseContext),
 128     .parser_init    = amr_parse_init,
 129     .parser_parse   = amr_parse,
 130     .parser_close   = ff_parse_close,
 131 };