avs.c

Go to the documentation of this file.

/*
 * AVS video decoder.
 * Copyright (c) 2006  Aurelien Jacobs <aurel@gnuage.org>
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * 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.
 *
 * FFmpeg is distributed in the hope that it will be useful,
 * 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
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */
 
#include "avcodec.h"
#include "codec_internal.h"
#include "decode.h"
#include "get_bits.h"
#include "libavutil/attributes.h"
 
typedef struct AvsContext {
    AVFrame *frame;
} AvsContext;
 
typedef enum {
    AVS_VIDEO     = 0x01,
    AVS_AUDIO     = 0x02,
    AVS_PALETTE   = 0x03,
    AVS_GAME_DATA = 0x04,
} AvsBlockType;
 
typedef enum {
    AVS_I_FRAME     = 0x00,
    AVS_P_FRAME_3X3 = 0x01,
    AVS_P_FRAME_2X2 = 0x02,
    AVS_P_FRAME_2X3 = 0x03,
} AvsVideoSubType;
 
 
static int avs_decode_frame(AVCodecContext * avctx, AVFrame *picture,
                            int *got_frame, AVPacket *avpkt)
{
    const uint8_t *buf = avpkt->data;
    const uint8_t *buf_end = avpkt->data + avpkt->size;
    int buf_size = avpkt->size;
    AvsContext *const avs = avctx->priv_data;
    AVFrame *const p =  avs->frame;
    const uint8_t *table, *vect;
    uint8_t *out;
    int i, j, x, y, stride, ret, vect_w = 3, vect_h = 3;
    AvsVideoSubType sub_type;
    AvsBlockType type;
    GetBitContext change_map = {0}; //init to silence warning
 
    if ((ret = ff_reget_buffer(avctx, p, 0)) < 0)
        return ret;
    p->pict_type = AV_PICTURE_TYPE_P;
    p->flags &= ~AV_FRAME_FLAG_KEY;
 
    out    = p->data[0];
    stride = p->linesize[0];
 
    if (buf_end - buf < 4)
        return AVERROR_INVALIDDATA;
    sub_type = buf[0];
    type = buf[1];
    buf += 4;
 
    if (type == AVS_PALETTE) {
        int first, last;
        uint32_t *pal = (uint32_t *) p->data[1];
 
        first = AV_RL16(buf);
        last = first + AV_RL16(buf + 2);
        if (first >= 256 || last > 256 || buf_end - buf < 4 + 4 + 3 * (last - first))
            return AVERROR_INVALIDDATA;
        buf += 4;
        for (i=first; i<last; i++, buf+=3) {
            pal[i] = (buf[0] << 18) | (buf[1] << 10) | (buf[2] << 2);
            pal[i] |= 0xFFU << 24 | (pal[i] >> 6) & 0x30303;
        }
 
        sub_type = buf[0];
        type = buf[1];
        buf += 4;
    }
 
    if (type != AVS_VIDEO)
        return AVERROR_INVALIDDATA;
 
    switch (sub_type) {
    case AVS_I_FRAME:
        p->pict_type = AV_PICTURE_TYPE_I;
        p->flags |= AV_FRAME_FLAG_KEY;
        av_fallthrough;
    case AVS_P_FRAME_3X3:
        vect_w = 3;
        vect_h = 3;
        break;
 
    case AVS_P_FRAME_2X2:
        vect_w = 2;
        vect_h = 2;
        break;
 
    case AVS_P_FRAME_2X3:
        vect_w = 2;
        vect_h = 3;
        break;
 
    default:
      return AVERROR_INVALIDDATA;
    }
 
    if (buf_end - buf < 256 * vect_w * vect_h)
        return AVERROR_INVALIDDATA;
    table = buf + (256 * vect_w * vect_h);
    if (sub_type != AVS_I_FRAME) {
        int map_size = ((318 / vect_w + 7) / 8) * (198 / vect_h);
        if (buf_end - table < map_size)
            return AVERROR_INVALIDDATA;
        init_get_bits(&change_map, table, map_size * 8);
        table += map_size;
    }
 
    for (y=0; y<198; y+=vect_h) {
        for (x=0; x<318; x+=vect_w) {
            if (sub_type == AVS_I_FRAME || get_bits1(&change_map)) {
                if (buf_end - table < 1)
                    return AVERROR_INVALIDDATA;
                vect = &buf[*table++ * (vect_w * vect_h)];
                for (j=0; j<vect_w; j++) {
                    out[(y + 0) * stride + x + j] = vect[(0 * vect_w) + j];
                    out[(y + 1) * stride + x + j] = vect[(1 * vect_w) + j];
                    if (vect_h == 3)
                        out[(y + 2) * stride + x + j] =
                            vect[(2 * vect_w) + j];
                }
            }
        }
        if (sub_type != AVS_I_FRAME)
            align_get_bits(&change_map);
    }
 
    if ((ret = av_frame_ref(picture, p)) < 0)
        return ret;
    *got_frame = 1;
 
    return buf_size;
}
 
static av_cold int avs_decode_init(AVCodecContext * avctx)
{
    AvsContext *s = avctx->priv_data;
 
    s->frame = av_frame_alloc();
    if (!s->frame)
        return AVERROR(ENOMEM);
 
    avctx->pix_fmt = AV_PIX_FMT_PAL8;
 
    return ff_set_dimensions(avctx, 318, 198);
}
 
static av_cold int avs_decode_end(AVCodecContext *avctx)
{
    AvsContext *s = avctx->priv_data;
    av_frame_free(&s->frame);
    return 0;
}
 
 
const FFCodec ff_avs_decoder = {
    .p.name         = "avs",
    CODEC_LONG_NAME("AVS (Audio Video Standard) video"),
    .p.type         = AVMEDIA_TYPE_VIDEO,
    .p.id           = AV_CODEC_ID_AVS,
    .priv_data_size = sizeof(AvsContext),
    .init           = avs_decode_init,
    FF_CODEC_DECODE_CB(avs_decode_frame),
    .close          = avs_decode_end,
    .p.capabilities = AV_CODEC_CAP_DR1,
};