roqaudioenc.c
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1 /*
2  * RoQ audio encoder
3  *
4  * Copyright (c) 2005 Eric Lasota
5  * Based on RoQ specs (c)2001 Tim Ferguson
6  *
7  * This file is part of Libav.
8  *
9  * Libav is free software; you can redistribute it and/or
10  * modify it under the terms of the GNU Lesser General Public
11  * License as published by the Free Software Foundation; either
12  * version 2.1 of the License, or (at your option) any later version.
13  *
14  * Libav is distributed in the hope that it will be useful,
15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17  * Lesser General Public License for more details.
18  *
19  * You should have received a copy of the GNU Lesser General Public
20  * License along with Libav; if not, write to the Free Software
21  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
22  */
23 
24 #include "libavutil/intmath.h"
25 #include "avcodec.h"
26 #include "bytestream.h"
27 
28 #define ROQ_FIRST_FRAME_SIZE (735*8)
29 #define ROQ_FRAME_SIZE 735
30 
31 
32 #define MAX_DPCM (127*127)
33 
34 
35 typedef struct
36 {
37  short lastSample[2];
39 
41 {
42  ROQDPCMContext *context = avctx->priv_data;
43 
44  if (avctx->channels > 2) {
45  av_log(avctx, AV_LOG_ERROR, "Audio must be mono or stereo\n");
46  return -1;
47  }
48  if (avctx->sample_rate != 22050) {
49  av_log(avctx, AV_LOG_ERROR, "Audio must be 22050 Hz\n");
50  return -1;
51  }
52  if (avctx->sample_fmt != AV_SAMPLE_FMT_S16) {
53  av_log(avctx, AV_LOG_ERROR, "Audio must be signed 16-bit\n");
54  return -1;
55  }
56 
58 
59  context->lastSample[0] = context->lastSample[1] = 0;
60 
62  avctx->coded_frame->key_frame= 1;
63 
64  return 0;
65 }
66 
67 static unsigned char dpcm_predict(short *previous, short current)
68 {
69  int diff;
70  int negative;
71  int result;
72  int predicted;
73 
74  diff = current - *previous;
75 
76  negative = diff<0;
77  diff = FFABS(diff);
78 
79  if (diff >= MAX_DPCM)
80  result = 127;
81  else {
82  result = ff_sqrt(diff);
83  result += diff > result*result+result;
84  }
85 
86  /* See if this overflows */
87  retry:
88  diff = result*result;
89  if (negative)
90  diff = -diff;
91  predicted = *previous + diff;
92 
93  /* If it overflows, back off a step */
94  if (predicted > 32767 || predicted < -32768) {
95  result--;
96  goto retry;
97  }
98 
99  /* Add the sign bit */
100  result |= negative << 7; //if (negative) result |= 128;
101 
102  *previous = predicted;
103 
104  return result;
105 }
106 
108  unsigned char *frame, int buf_size, void *data)
109 {
110  int i, samples, stereo, ch;
111  const short *in;
112  unsigned char *out;
113 
114  ROQDPCMContext *context = avctx->priv_data;
115 
116  stereo = (avctx->channels == 2);
117 
118  if (stereo) {
119  context->lastSample[0] &= 0xFF00;
120  context->lastSample[1] &= 0xFF00;
121  }
122 
123  out = frame;
124  in = data;
125 
126  bytestream_put_byte(&out, stereo ? 0x21 : 0x20);
127  bytestream_put_byte(&out, 0x10);
128  bytestream_put_le32(&out, avctx->frame_size*avctx->channels);
129 
130  if (stereo) {
131  bytestream_put_byte(&out, (context->lastSample[1])>>8);
132  bytestream_put_byte(&out, (context->lastSample[0])>>8);
133  } else
134  bytestream_put_le16(&out, context->lastSample[0]);
135 
136  /* Write the actual samples */
137  samples = avctx->frame_size;
138  for (i=0; i<samples; i++)
139  for (ch=0; ch<avctx->channels; ch++)
140  *out++ = dpcm_predict(&context->lastSample[ch], *in++);
141 
142  /* Use smaller frames from now on */
143  avctx->frame_size = ROQ_FRAME_SIZE;
144 
145  /* Return the result size */
146  return out - frame;
147 }
148 
150 {
151  av_freep(&avctx->coded_frame);
152 
153  return 0;
154 }
155 
157  .name = "roq_dpcm",
158  .type = AVMEDIA_TYPE_AUDIO,
159  .id = CODEC_ID_ROQ_DPCM,
160  .priv_data_size = sizeof(ROQDPCMContext),
162  .encode = roq_dpcm_encode_frame,
164  .sample_fmts = (const enum AVSampleFormat[]){AV_SAMPLE_FMT_S16,AV_SAMPLE_FMT_NONE},
165  .long_name = NULL_IF_CONFIG_SMALL("id RoQ DPCM"),
166 };
static short * samples
Definition: ffmpeg.c:233
AVFrame * coded_frame
the picture in the bitstream
Definition: avcodec.h:2000
signed 16 bits
Definition: samplefmt.h:30
AVCodec.
Definition: avcodec.h:3189
short lastSample[2]
Definition: roqaudioenc.c:37
void av_freep(void *arg)
Free a memory block which has been allocated with av_malloc(z)() or av_realloc() and set the pointer ...
Definition: mem.c:147
static av_const unsigned int ff_sqrt(unsigned int a)
Definition: intmath.h:64
enum AVSampleFormat sample_fmt
audio sample format
Definition: avcodec.h:1464
#define av_cold
Definition: attributes.h:71
static av_cold int roq_dpcm_encode_close(AVCodecContext *avctx)
Definition: roqaudioenc.c:149
const char data[16]
Definition: mxf.c:60
static int init(AVCodecParserContext *s)
Definition: h264_parser.c:336
#define NULL_IF_CONFIG_SMALL(x)
Return NULL if CONFIG_SMALL is true, otherwise the argument without modification. ...
Definition: internal.h:191
void av_log(void *avcl, int level, const char *fmt,...)
Definition: log.c:140
const char * name
Name of the codec implementation.
Definition: avcodec.h:3196
AVFrame * avcodec_alloc_frame(void)
Allocate an AVFrame and set its fields to default values.
Definition: utils.c:618
#define ROQ_FIRST_FRAME_SIZE
Definition: roqaudioenc.c:28
#define FFABS(a)
Definition: common.h:50
static av_cold int roq_dpcm_encode_init(AVCodecContext *avctx)
Definition: roqaudioenc.c:40
int frame_size
Samples per packet, initialized when calling 'init'.
Definition: avcodec.h:1470
external API header
static int roq_dpcm_encode_frame(AVCodecContext *avctx, unsigned char *frame, int buf_size, void *data)
Definition: roqaudioenc.c:107
int sample_rate
samples per second
Definition: avcodec.h:1456
main external API structure.
Definition: avcodec.h:1329
static void close(AVCodecParserContext *s)
Definition: h264_parser.c:327
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:111
static unsigned char dpcm_predict(short *previous, short current)
Definition: roqaudioenc.c:67
AVSampleFormat
all in native-endian format
Definition: samplefmt.h:27
void * priv_data
Definition: avcodec.h:1531
int channels
number of audio channels
Definition: avcodec.h:1457
int key_frame
1 -> keyframe, 0-> not
Definition: avcodec.h:1022
#define ROQ_FRAME_SIZE
Definition: roqaudioenc.c:29
AVCodec ff_roq_dpcm_encoder
Definition: roqaudioenc.c:156
#define MAX_DPCM
Definition: roqaudioenc.c:32