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 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
  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 av_cold 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     .long_name = "id RoQ DPCM",
 178 };