bmvaudio.c 2.82 KB
Newer Older
1 2 3 4
/*
 * Discworld II BMV audio decoder
 * Copyright (c) 2011 Konstantin Shishkov
 *
5
 * This file is part of FFmpeg.
6
 *
7
 * FFmpeg is free software; you can redistribute it and/or
8 9 10 11
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
12
 * FFmpeg is distributed in the hope that it will be useful,
13 14 15 16 17
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * 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 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include "libavutil/channel_layout.h"
#include "libavutil/common.h"

#include "avcodec.h"
#include "internal.h"

static const int bmv_aud_mults[16] = {
    16512, 8256, 4128, 2064, 1032, 516, 258, 192, 129, 88, 64, 56, 48, 40, 36, 32
};

static av_cold int bmv_aud_decode_init(AVCodecContext *avctx)
{
    avctx->channels       = 2;
    avctx->channel_layout = AV_CH_LAYOUT_STEREO;
    avctx->sample_fmt     = AV_SAMPLE_FMT_S16;

    return 0;
}

static int bmv_aud_decode_frame(AVCodecContext *avctx, void *data,
                                int *got_frame_ptr, AVPacket *avpkt)
{
    AVFrame *frame     = data;
    const uint8_t *buf = avpkt->data;
    int buf_size = avpkt->size;
    int blocks = 0, total_blocks, i;
    int ret;
    int16_t *output_samples;
    int scale[2];

    total_blocks = *buf++;
    if (buf_size < total_blocks * 65 + 1) {
        av_log(avctx, AV_LOG_ERROR, "expected %d bytes, got %d\n",
               total_blocks * 65 + 1, buf_size);
        return AVERROR_INVALIDDATA;
    }

    /* get output buffer */
    frame->nb_samples = total_blocks * 32;
61
    if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87
        return ret;
    output_samples = (int16_t *)frame->data[0];

    for (blocks = 0; blocks < total_blocks; blocks++) {
        uint8_t code = *buf++;
        code = (code >> 1) | (code << 7);
        scale[0] = bmv_aud_mults[code & 0xF];
        scale[1] = bmv_aud_mults[code >> 4];
        for (i = 0; i < 32; i++) {
            *output_samples++ = av_clip_int16((scale[0] * (int8_t)*buf++) >> 5);
            *output_samples++ = av_clip_int16((scale[1] * (int8_t)*buf++) >> 5);
        }
    }

    *got_frame_ptr = 1;

    return buf_size;
}

AVCodec ff_bmv_audio_decoder = {
    .name           = "bmv_audio",
    .long_name      = NULL_IF_CONFIG_SMALL("Discworld II BMV audio"),
    .type           = AVMEDIA_TYPE_AUDIO,
    .id             = AV_CODEC_ID_BMV_AUDIO,
    .init           = bmv_aud_decode_init,
    .decode         = bmv_aud_decode_frame,
88
    .capabilities   = AV_CODEC_CAP_DR1,
89
};