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ffmpeg / libavcodec / kgv1dec.c @ 72415b2a

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/*
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 * Kega Game Video (KGV1) decoder
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 * Copyright (c) 2010 Daniel Verkamp
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 *
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 * This file is part of FFmpeg.
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 *
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 * FFmpeg is free software; you can redistribute it and/or
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 * modify it under the terms of the GNU Lesser General Public
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 * License as published by the Free Software Foundation; either
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 * version 2.1 of the License, or (at your option) any later version.
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 *
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 * FFmpeg is distributed in the hope that it will be useful,
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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 * Lesser General Public License for more details.
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 *
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 * You should have received a copy of the GNU Lesser General Public
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 * License along with FFmpeg; if not, write to the Free Software
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 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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 */
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/**
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 * @file libavcodec/kgv1dec.c
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 * Kega Game Video decoder
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 */
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#include "libavutil/intreadwrite.h"
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#include "avcodec.h"
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typedef struct {
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    AVCodecContext *avctx;
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    AVFrame pic;
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    uint16_t *prev, *cur;
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} KgvContext;
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static int decode_frame(AVCodecContext *avctx, void *data, int *data_size, AVPacket *avpkt)
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{
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    const uint8_t *buf = avpkt->data;
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    const uint8_t *buf_end = buf + avpkt->size;
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    KgvContext * const c = avctx->priv_data;
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    int offsets[7];
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    uint16_t *out, *prev;
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    int outcnt = 0, maxcnt;
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    int w, h, i;
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    if (avpkt->size < 2)
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        return -1;
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    w = (buf[0] + 1) * 8;
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    h = (buf[1] + 1) * 8;
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    buf += 2;
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    if (avcodec_check_dimensions(avctx, w, h))
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        return -1;
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    if (w != avctx->width || h != avctx->height)
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        avcodec_set_dimensions(avctx, w, h);
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    maxcnt = w * h;
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    out = av_realloc(c->cur, w * h * 2);
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    if (!out)
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        return -1;
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    c->cur = out;
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    prev = av_realloc(c->prev, w * h * 2);
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    if (!prev)
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        return -1;
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    c->prev = prev;
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    for (i = 0; i < 7; i++)
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        offsets[i] = -1;
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    while (outcnt < maxcnt && buf_end - 2 > buf) {
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        int code = AV_RL16(buf);
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        buf += 2;
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        if (!(code & 0x8000)) {
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            out[outcnt++] = code; // rgb555 pixel coded directly
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        } else {
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            int count;
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            uint16_t *inp;
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            if ((code & 0x6000) == 0x6000) {
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                // copy from previous frame
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                int oidx = (code >> 10) & 7;
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                int start;
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                count = (code & 0x3FF) + 3;
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                if (offsets[oidx] < 0) {
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                    if (buf_end - 3 < buf)
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                        break;
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                    offsets[oidx] = AV_RL24(buf);
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                    buf += 3;
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                }
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                start = (outcnt + offsets[oidx]) % maxcnt;
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                if (maxcnt - start < count)
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                    break;
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                inp = prev + start;
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            } else {
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                // copy from earlier in this frame
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                int offset = (code & 0x1FFF) + 1;
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                if (!(code & 0x6000)) {
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                    count = 2;
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                } else if ((code & 0x6000) == 0x2000) {
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                    count = 3;
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                } else {
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                    if (buf_end - 1 < buf)
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                        break;
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                    count = 4 + *buf++;
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                }
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                if (outcnt < offset)
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                    break;
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                inp = out + outcnt - offset;
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            }
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            if (maxcnt - outcnt < count)
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                break;
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            for (i = 0; i < count; i++)
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                out[outcnt++] = inp[i];
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        }
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    }
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    if (outcnt - maxcnt)
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        av_log(avctx, AV_LOG_DEBUG, "frame finished with %d diff\n", outcnt - maxcnt);
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    c->pic.data[0]     = (uint8_t *)c->cur;
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    c->pic.linesize[0] = w * 2;
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    *data_size = sizeof(AVFrame);
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    *(AVFrame*)data = c->pic;
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    FFSWAP(uint16_t *, c->cur, c->prev);
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    return avpkt->size;
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}
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static av_cold int decode_init(AVCodecContext *avctx)
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{
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    KgvContext * const c = avctx->priv_data;
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    c->avctx = avctx;
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    avctx->pix_fmt = PIX_FMT_RGB555;
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    return 0;
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}
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static av_cold int decode_end(AVCodecContext *avctx)
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{
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    KgvContext * const c = avctx->priv_data;
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    av_freep(&c->cur);
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    av_freep(&c->prev);
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    return 0;
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}
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AVCodec kgv1_decoder = {
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    "kgv1",
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    AVMEDIA_TYPE_VIDEO,
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    CODEC_ID_KGV1,
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    sizeof(KgvContext),
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    decode_init,
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    NULL,
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    decode_end,
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    decode_frame,
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    .long_name = NULL_IF_CONFIG_SMALL("Kega Game Video"),
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};