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  1. /*
  2.  * Discworld II BMV audio decoder
  3.  * Copyright (c) 2011 Konstantin Shishkov
  4.  *
  5.  * This file is part of FFmpeg.
  6.  *
  7.  * FFmpeg is free software; you can redistribute it and/or
  8.  * modify it under the terms of the GNU Lesser General Public
  9.  * License as published by the Free Software Foundation; either
  10.  * version 2.1 of the License, or (at your option) any later version.
  11.  *
  12.  * FFmpeg is distributed in the hope that it will be useful,
  13.  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14.  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15.  * Lesser General Public License for more details.
  16.  *
  17.  * You should have received a copy of the GNU Lesser General Public
  18.  * License along with FFmpeg; if not, write to the Free Software
  19.  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20.  */
  21.  
  22. #include "libavutil/channel_layout.h"
  23. #include "libavutil/common.h"
  24.  
  25. #include "avcodec.h"
  26. #include "internal.h"
  27.  
  28. static const int bmv_aud_mults[16] = {
  29.     16512, 8256, 4128, 2064, 1032, 516, 258, 192, 129, 88, 64, 56, 48, 40, 36, 32
  30. };
  31.  
  32. static av_cold int bmv_aud_decode_init(AVCodecContext *avctx)
  33. {
  34.     avctx->channels       = 2;
  35.     avctx->channel_layout = AV_CH_LAYOUT_STEREO;
  36.     avctx->sample_fmt     = AV_SAMPLE_FMT_S16;
  37.  
  38.     return 0;
  39. }
  40.  
  41. static int bmv_aud_decode_frame(AVCodecContext *avctx, void *data,
  42.                                 int *got_frame_ptr, AVPacket *avpkt)
  43. {
  44.     AVFrame *frame     = data;
  45.     const uint8_t *buf = avpkt->data;
  46.     int buf_size = avpkt->size;
  47.     int blocks = 0, total_blocks, i;
  48.     int ret;
  49.     int16_t *output_samples;
  50.     int scale[2];
  51.  
  52.     total_blocks = *buf++;
  53.     if (buf_size < total_blocks * 65 + 1) {
  54.         av_log(avctx, AV_LOG_ERROR, "expected %d bytes, got %d\n",
  55.                total_blocks * 65 + 1, buf_size);
  56.         return AVERROR_INVALIDDATA;
  57.     }
  58.  
  59.     /* get output buffer */
  60.     frame->nb_samples = total_blocks * 32;
  61.     if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
  62.         return ret;
  63.     output_samples = (int16_t *)frame->data[0];
  64.  
  65.     for (blocks = 0; blocks < total_blocks; blocks++) {
  66.         uint8_t code = *buf++;
  67.         code = (code >> 1) | (code << 7);
  68.         scale[0] = bmv_aud_mults[code & 0xF];
  69.         scale[1] = bmv_aud_mults[code >> 4];
  70.         for (i = 0; i < 32; i++) {
  71.             *output_samples++ = av_clip_int16((scale[0] * (int8_t)*buf++) >> 5);
  72.             *output_samples++ = av_clip_int16((scale[1] * (int8_t)*buf++) >> 5);
  73.         }
  74.     }
  75.  
  76.     *got_frame_ptr = 1;
  77.  
  78.     return buf_size;
  79. }
  80.  
  81. AVCodec ff_bmv_audio_decoder = {
  82.     .name           = "bmv_audio",
  83.     .long_name      = NULL_IF_CONFIG_SMALL("Discworld II BMV audio"),
  84.     .type           = AVMEDIA_TYPE_AUDIO,
  85.     .id             = AV_CODEC_ID_BMV_AUDIO,
  86.     .init           = bmv_aud_decode_init,
  87.     .decode         = bmv_aud_decode_frame,
  88.     .capabilities   = AV_CODEC_CAP_DR1,
  89. };
  90.