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)
32static unsigned char dpcmValues[MAX_DPCM];
33
34
35typedef struct
36{
37    short lastSample[2];
38} ROQDPCMContext;
39
40static av_cold 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
52static av_cold int roq_dpcm_encode_init(AVCodecContext *avctx)
53{
54    ROQDPCMContext *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
81static 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
119static 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 *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
161static av_cold int roq_dpcm_encode_close(AVCodecContext *avctx)
162{
163    av_freep(&avctx->coded_frame);
164
165    return 0;
166}
167
168AVCodec roq_dpcm_encoder = {
169    "roq_dpcm",
170    CODEC_TYPE_AUDIO,
171    CODEC_ID_ROQ_DPCM,
172    sizeof(ROQDPCMContext),
173    roq_dpcm_encode_init,
174    roq_dpcm_encode_frame,
175    roq_dpcm_encode_close,
176    NULL,
177    .sample_fmts = (enum SampleFormat[]){SAMPLE_FMT_S16,SAMPLE_FMT_NONE},
178    .long_name = NULL_IF_CONFIG_SMALL("id RoQ DPCM"),
179};
180