s302m.c
Go to the documentation of this file.
1 /*
2  * SMPTE 302M decoder
3  * Copyright (c) 2008 Laurent Aimar <fenrir@videolan.org>
4  * Copyright (c) 2009 Baptiste Coudurier <baptiste.coudurier@gmail.com>
5  *
6  * This file is part of Libav.
7  *
8  * Libav is free software; you can redistribute it and/or
9  * modify it under the terms of the GNU Lesser General Public
10  * License as published by the Free Software Foundation; either
11  * version 2.1 of the License, or (at your option) any later version.
12  *
13  * Libav is distributed in the hope that it will be useful,
14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16  * Lesser General Public License for more details.
17  *
18  * You should have received a copy of the GNU Lesser General Public
19  * License along with Libav; if not, write to the Free Software
20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21  */
22 
23 #include "libavutil/intreadwrite.h"
24 #include "avcodec.h"
25 
26 #define AES3_HEADER_LEN 4
27 
28 typedef struct S302MDecodeContext {
31 
32 static int s302m_parse_frame_header(AVCodecContext *avctx, const uint8_t *buf,
33  int buf_size)
34 {
35  uint32_t h;
36  int frame_size, channels, bits;
37 
38  if (buf_size <= AES3_HEADER_LEN) {
39  av_log(avctx, AV_LOG_ERROR, "frame is too short\n");
40  return AVERROR_INVALIDDATA;
41  }
42 
43  /*
44  * AES3 header :
45  * size: 16
46  * number channels 2
47  * channel_id 8
48  * bits per samples 2
49  * alignments 4
50  */
51 
52  h = AV_RB32(buf);
53  frame_size = (h >> 16) & 0xffff;
54  channels = ((h >> 14) & 0x0003) * 2 + 2;
55  bits = ((h >> 4) & 0x0003) * 4 + 16;
56 
57  if (AES3_HEADER_LEN + frame_size != buf_size || bits > 24) {
58  av_log(avctx, AV_LOG_ERROR, "frame has invalid header\n");
59  return AVERROR_INVALIDDATA;
60  }
61 
62  /* Set output properties */
63  avctx->bits_per_coded_sample = bits;
64  if (bits > 16)
66  else
68 
69  avctx->channels = channels;
70  avctx->sample_rate = 48000;
71  avctx->bit_rate = 48000 * avctx->channels * (avctx->bits_per_coded_sample + 4) +
72  32 * (48000 / (buf_size * 8 /
73  (avctx->channels *
74  (avctx->bits_per_coded_sample + 4))));
75 
76  return frame_size;
77 }
78 
79 static int s302m_decode_frame(AVCodecContext *avctx, void *data,
80  int *got_frame_ptr, AVPacket *avpkt)
81 {
82  S302MDecodeContext *s = avctx->priv_data;
83  const uint8_t *buf = avpkt->data;
84  int buf_size = avpkt->size;
85  int block_size, ret;
86 
87  int frame_size = s302m_parse_frame_header(avctx, buf, buf_size);
88  if (frame_size < 0)
89  return frame_size;
90 
91  buf_size -= AES3_HEADER_LEN;
92  buf += AES3_HEADER_LEN;
93 
94  /* get output buffer */
95  block_size = (avctx->bits_per_coded_sample + 4) / 4;
96  s->frame.nb_samples = 2 * (buf_size / block_size) / avctx->channels;
97  if ((ret = avctx->get_buffer(avctx, &s->frame)) < 0) {
98  av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
99  return ret;
100  }
101 
102  buf_size = (s->frame.nb_samples * avctx->channels / 2) * block_size;
103 
104  if (avctx->bits_per_coded_sample == 24) {
105  uint32_t *o = (uint32_t *)s->frame.data[0];
106  for (; buf_size > 6; buf_size -= 7) {
107  *o++ = (av_reverse[buf[2]] << 24) |
108  (av_reverse[buf[1]] << 16) |
109  (av_reverse[buf[0]] << 8);
110  *o++ = (av_reverse[buf[6] & 0xf0] << 28) |
111  (av_reverse[buf[5]] << 20) |
112  (av_reverse[buf[4]] << 12) |
113  (av_reverse[buf[3] & 0x0f] << 4);
114  buf += 7;
115  }
116  } else if (avctx->bits_per_coded_sample == 20) {
117  uint32_t *o = (uint32_t *)s->frame.data[0];
118  for (; buf_size > 5; buf_size -= 6) {
119  *o++ = (av_reverse[buf[2] & 0xf0] << 28) |
120  (av_reverse[buf[1]] << 20) |
121  (av_reverse[buf[0]] << 12);
122  *o++ = (av_reverse[buf[5] & 0xf0] << 28) |
123  (av_reverse[buf[4]] << 20) |
124  (av_reverse[buf[3]] << 12);
125  buf += 6;
126  }
127  } else {
128  uint16_t *o = (uint16_t *)s->frame.data[0];
129  for (; buf_size > 4; buf_size -= 5) {
130  *o++ = (av_reverse[buf[1]] << 8) |
131  av_reverse[buf[0]];
132  *o++ = (av_reverse[buf[4] & 0xf0] << 12) |
133  (av_reverse[buf[3]] << 4) |
134  (av_reverse[buf[2]] >> 4);
135  buf += 5;
136  }
137  }
138 
139  *got_frame_ptr = 1;
140  *(AVFrame *)data = s->frame;
141 
142  return avpkt->size;
143 }
144 
146 {
147  S302MDecodeContext *s = avctx->priv_data;
148 
150  avctx->coded_frame = &s->frame;
151 
152  return 0;
153 }
154 
155 
157  .name = "s302m",
158  .type = AVMEDIA_TYPE_AUDIO,
159  .id = CODEC_ID_S302M,
160  .priv_data_size = sizeof(S302MDecodeContext),
163  .capabilities = CODEC_CAP_DR1,
164  .long_name = NULL_IF_CONFIG_SMALL("SMPTE 302M"),
165 };