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 "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
35typedef struct
36{
37    short lastSample[2];
38} ROQDPCMContext;
39
40static av_cold int roq_dpcm_encode_init(AVCodecContext *avctx)
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 != SAMPLE_FMT_S16) {
53        av_log(avctx, AV_LOG_ERROR, "Audio must be signed 16-bit\n");
54        return -1;
55    }
56
57    avctx->frame_size = ROQ_FIRST_FRAME_SIZE;
58
59    context->lastSample[0] = context->lastSample[1] = 0;
60
61    avctx->coded_frame= avcodec_alloc_frame();
62    avctx->coded_frame->key_frame= 1;
63
64    return 0;
65}
66
67static 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
107static int roq_dpcm_encode_frame(AVCodecContext *avctx,
108                unsigned char *frame, int buf_size, void *data)
109{
110    int i, samples, stereo, ch;
111    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
149static av_cold int roq_dpcm_encode_close(AVCodecContext *avctx)
150{
151    av_freep(&avctx->coded_frame);
152
153    return 0;
154}
155
156AVCodec roq_dpcm_encoder = {
157    "roq_dpcm",
158    AVMEDIA_TYPE_AUDIO,
159    CODEC_ID_ROQ_DPCM,
160    sizeof(ROQDPCMContext),
161    roq_dpcm_encode_init,
162    roq_dpcm_encode_frame,
163    roq_dpcm_encode_close,
164    NULL,
165    .sample_fmts = (const enum SampleFormat[]){SAMPLE_FMT_S16,SAMPLE_FMT_NONE},
166    .long_name = NULL_IF_CONFIG_SMALL("id RoQ DPCM"),
167};
168