RoQ audio encoder
[libav.git] / libavcodec / roqaudioenc.c
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 FFmpeg.
8 *
9 * FFmpeg 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 * FFmpeg 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 FFmpeg; if not, write to the Free Software
21 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
22 */
23
24 #include "avcodec.h"
25 #include "bytestream.h"
26
27 #define ROQ_FIRST_FRAME_SIZE (735*8)
28 #define ROQ_FRAME_SIZE 735
29
30
31 #define MAX_DPCM (127*127)
32 static unsigned char dpcmValues[MAX_DPCM];
33
34
35 typedef struct
36 {
37 short lastSample[2];
38 } ROQDPCMContext_t;
39
40 static void roq_dpcm_table_init(void)
41 {
42 int i;
43
44 /* Create a table of quick DPCM values */
45 for (i=0; i<MAX_DPCM; i++) {
46 int s= ff_sqrt(i);
47 int mid= s*s + s;
48 dpcmValues[i]= s + (i>mid);
49 }
50 }
51
52 static int roq_dpcm_encode_init(AVCodecContext *avctx)
53 {
54 ROQDPCMContext_t *context = avctx->priv_data;
55
56 if (avctx->channels > 2) {
57 av_log(avctx, AV_LOG_ERROR, "Audio must be mono or stereo\n");
58 return -1;
59 }
60 if (avctx->sample_rate != 22050) {
61 av_log(avctx, AV_LOG_ERROR, "Audio must be 22050 Hz\n");
62 return -1;
63 }
64 if (avctx->sample_fmt != SAMPLE_FMT_S16) {
65 av_log(avctx, AV_LOG_ERROR, "Audio must be signed 16-bit\n");
66 return -1;
67 }
68
69 roq_dpcm_table_init();
70
71 avctx->frame_size = ROQ_FIRST_FRAME_SIZE;
72
73 context->lastSample[0] = context->lastSample[1] = 0;
74
75 avctx->coded_frame= avcodec_alloc_frame();
76 avctx->coded_frame->key_frame= 1;
77
78 return 0;
79 }
80
81 static unsigned char dpcm_predict(short *previous, short current)
82 {
83 int diff;
84 int negative;
85 int result;
86 int predicted;
87
88 diff = current - *previous;
89
90 negative = diff<0;
91 diff = FFABS(diff);
92
93 if (diff >= MAX_DPCM)
94 result = 127;
95 else
96 result = dpcmValues[diff];
97
98 /* See if this overflows */
99 retry:
100 diff = result*result;
101 if (negative)
102 diff = -diff;
103 predicted = *previous + diff;
104
105 /* If it overflows, back off a step */
106 if (predicted > 32767 || predicted < -32768) {
107 result--;
108 goto retry;
109 }
110
111 /* Add the sign bit */
112 result |= negative << 7; //if (negative) result |= 128;
113
114 *previous = predicted;
115
116 return result;
117 }
118
119 static int roq_dpcm_encode_frame(AVCodecContext *avctx,
120 unsigned char *frame, int buf_size, void *data)
121 {
122 int i, samples, stereo, ch;
123 short *in;
124 unsigned char *out;
125
126 ROQDPCMContext_t *context = avctx->priv_data;
127
128 stereo = (avctx->channels == 2);
129
130 if (stereo) {
131 context->lastSample[0] &= 0xFF00;
132 context->lastSample[1] &= 0xFF00;
133 }
134
135 out = frame;
136 in = data;
137
138 bytestream_put_byte(&out, stereo ? 0x21 : 0x20);
139 bytestream_put_byte(&out, 0x10);
140 bytestream_put_le32(&out, avctx->frame_size*avctx->channels);
141
142 if (stereo) {
143 bytestream_put_byte(&out, (context->lastSample[1])>>8);
144 bytestream_put_byte(&out, (context->lastSample[0])>>8);
145 } else
146 bytestream_put_le16(&out, context->lastSample[0]);
147
148 /* Write the actual samples */
149 samples = avctx->frame_size;
150 for (i=0; i<samples; i++)
151 for (ch=0; ch<avctx->channels; ch++)
152 *out++ = dpcm_predict(&context->lastSample[ch], *in++);
153
154 /* Use smaller frames from now on */
155 avctx->frame_size = ROQ_FRAME_SIZE;
156
157 /* Return the result size */
158 return out - frame;
159 }
160
161 static int roq_dpcm_encode_close(AVCodecContext *avctx)
162 {
163 av_freep(&avctx->coded_frame);
164
165 return 0;
166 }
167
168 AVCodec roq_dpcm_encoder = {
169 "roq_dpcm",
170 CODEC_TYPE_AUDIO,
171 CODEC_ID_ROQ_DPCM,
172 sizeof(ROQDPCMContext_t),
173 roq_dpcm_encode_init,
174 roq_dpcm_encode_frame,
175 roq_dpcm_encode_close,
176 NULL,
177 };