PeerStreamer

/*

 * Kega Game Video (KGV1) decoder

 * Copyright (c) 2010 Daniel Verkamp

 *

 * 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

 */

/**

 * @file

 * Kega Game Video decoder

 */

#include "libavutil/intreadwrite.h"

#include "libavcore/imgutils.h"

#include "avcodec.h"

typedef struct {

    AVCodecContext *avctx;

    AVFrame pic;

    uint16_t *prev, *cur;

} KgvContext;

static int decode_frame(AVCodecContext *avctx, void *data, int *data_size, AVPacket *avpkt)

{

    const uint8_t *buf = avpkt->data;

    const uint8_t *buf_end = buf + avpkt->size;

    KgvContext * const c = avctx->priv_data;

    int offsets[7];

    uint16_t *out, *prev;

    int outcnt = 0, maxcnt;

    int w, h, i;

    if (avpkt->size < 2)

        return -1;

    w = (buf[0] + 1) * 8;

    h = (buf[1] + 1) * 8;

    buf += 2;

    if (av_image_check_size(w, h, 0, avctx))

        return -1;

    if (w != avctx->width || h != avctx->height)

        avcodec_set_dimensions(avctx, w, h);

    maxcnt = w * h;

    out = av_realloc(c->cur, w * h * 2);

    if (!out)

        return -1;

    c->cur = out;

    prev = av_realloc(c->prev, w * h * 2);

    if (!prev)

        return -1;

    c->prev = prev;

    for (i = 0; i < 7; i++)

        offsets[i] = -1;

    while (outcnt < maxcnt && buf_end - 2 > buf) {

        int code = AV_RL16(buf);

        buf += 2;

        if (!(code & 0x8000)) {

            out[outcnt++] = code; // rgb555 pixel coded directly

        } else {

            int count;

            uint16_t *inp;

            if ((code & 0x6000) == 0x6000) {

                // copy from previous frame

                int oidx = (code >> 10) & 7;

                int start;

                count = (code & 0x3FF) + 3;

                if (offsets[oidx] < 0) {

                    if (buf_end - 3 < buf)

                        break;

                    offsets[oidx] = AV_RL24(buf);

                    buf += 3;

                }

                start = (outcnt + offsets[oidx]) % maxcnt;

                if (maxcnt - start < count)

                    break;

                inp = prev + start;

            } else {

                // copy from earlier in this frame

                int offset = (code & 0x1FFF) + 1;

                if (!(code & 0x6000)) {

                    count = 2;

                } else if ((code & 0x6000) == 0x2000) {

                    count = 3;

                } else {

                    if (buf_end - 1 < buf)

                        break;

                    count = 4 + *buf++;

                }

                if (outcnt < offset)

                    break;

                inp = out + outcnt - offset;

            }

            if (maxcnt - outcnt < count)

                break;

            for (i = 0; i < count; i++)

                out[outcnt++] = inp[i];

        }

    }

    if (outcnt - maxcnt)

        av_log(avctx, AV_LOG_DEBUG, "frame finished with %d diff\n", outcnt - maxcnt);

    c->pic.data[0]     = (uint8_t *)c->cur;

    c->pic.linesize[0] = w * 2;

    *data_size = sizeof(AVFrame);

    *(AVFrame*)data = c->pic;

    FFSWAP(uint16_t *, c->cur, c->prev);

    return avpkt->size;

}

static av_cold int decode_init(AVCodecContext *avctx)

{

    KgvContext * const c = avctx->priv_data;

    c->avctx = avctx;

    avctx->pix_fmt = PIX_FMT_RGB555;

    return 0;

}

static av_cold int decode_end(AVCodecContext *avctx)

{

    KgvContext * const c = avctx->priv_data;

    av_freep(&c->cur);

    av_freep(&c->prev);

    return 0;

}

AVCodec ff_kgv1_decoder = {

    "kgv1",

    AVMEDIA_TYPE_VIDEO,

    CODEC_ID_KGV1,

    sizeof(KgvContext),

    decode_init,

    NULL,

    decode_end,

    decode_frame,

    .max_lowres = 1,

    .long_name = NULL_IF_CONFIG_SMALL("Kega Game Video"),

};