libavcodec/bmvaudio.c

   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 "codec_internal.h"
  27 #include "decode.h"
  28
  29 static const int bmv_aud_mults[16] = {
  30     16512, 8256, 4128, 2064, 1032, 516, 258, 192, 129, 88, 64, 56, 48, 40, 36, 32
  31 };
  32
  33 static av_cold int bmv_aud_decode_init(AVCodecContext *avctx)
  34 {
  35     av_channel_layout_uninit(&avctx->ch_layout);
  36     avctx->ch_layout      = (AVChannelLayout)AV_CHANNEL_LAYOUT_STEREO;
  37     avctx->sample_fmt     = AV_SAMPLE_FMT_S16;
  38
  39     return 0;
  40 }
  41
  42 static int bmv_aud_decode_frame(AVCodecContext *avctx, AVFrame *frame,
  43                                 int *got_frame_ptr, AVPacket *avpkt)
  44 {
  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 const FFCodec ff_bmv_audio_decoder = {
  82     .p.name         = "bmv_audio",
  83     CODEC_LONG_NAME("Discworld II BMV audio"),
  84     .p.type         = AVMEDIA_TYPE_AUDIO,
  85     .p.id           = AV_CODEC_ID_BMV_AUDIO,
  86     .init           = bmv_aud_decode_init,
  87     FF_CODEC_DECODE_CB(bmv_aud_decode_frame),
  88     .p.capabilities = AV_CODEC_CAP_DR1 | AV_CODEC_CAP_CHANNEL_CONF,
  89 };