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ffmpeg / libavcodec / wnv1.c @ a8a15e9d

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/*
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 * Winnov WNV1 codec
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 * Copyright (c) 2005 Konstantin Shishkov
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 *
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 * This library 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 of the License, or (at your option) any later version.
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 *
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 * This library 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 this library; if not, write to the Free Software
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 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
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 *
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 */
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/**
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 * @file wnv1.c
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 * Winnov WNV1 codec.
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 */
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#include "avcodec.h"
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#include "common.h"
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typedef struct WNV1Context{
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    AVCodecContext *avctx;
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    AVFrame pic;
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    int shift;
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    /* bit buffer */
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    unsigned long bitbuf;
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    int bits;
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    uint8_t *buf;
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} WNV1Context;
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/* returns modified base_value */
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static inline int wnv1_get_code(WNV1Context *w, int base_value)
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{
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    int v = 0;
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    if (w->bits < 16) { /* need to fill bit buffer */
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        w->bitbuf |= LE_16(w->buf) << w->bits;
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        w->buf += 2;
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        w->bits += 16;
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    }
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    /* escape code */
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    if ((w->bitbuf & 0xFF) == 0xFF) {
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        w->bitbuf >>= 8;
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        w->bits -= 8;
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        if (w->bits < 16) { /* need to fill bit buffer */
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            w->bitbuf |= LE_16(w->buf) << w->bits;
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            w->buf += 2;
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            w->bits += 16;
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        }
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        v = w->bitbuf & (0xFF >> w->shift);
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        w->bitbuf >>= 8 - w->shift;
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        w->bits -= 8 - w->shift;
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        return v << w->shift;
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    }
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    /* zero code */
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    if (!(w->bitbuf & 1)) {
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        w->bitbuf >>= 1;
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        w->bits--;
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        return base_value;
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    }
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    /* reversed unary code and sign */
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    while (w->bits && w->bitbuf & 1) {
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        w->bitbuf >>= 1;
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        w->bits--;
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        v++;
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    }
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    w->bitbuf >>= 1;
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    w->bits--;
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    if(w->bitbuf & 1)
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        v = -v;
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    w->bitbuf >>= 1;
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    w->bits--;
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    v <<= w->shift;
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    return base_value + v;
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}
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static int decode_frame(AVCodecContext *avctx, 
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                        void *data, int *data_size,
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                        uint8_t *buf, int buf_size)
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{
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    WNV1Context * const l = avctx->priv_data;
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    AVFrame * const p= (AVFrame*)&l->pic;
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    unsigned char *Y,*U,*V;
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    int i, j;
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    int prev_y = 0, prev_u = 0, prev_v = 0;
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    if(p->data[0])
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        avctx->release_buffer(avctx, p);
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    p->reference = 0;
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    if(avctx->get_buffer(avctx, p) < 0){
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        av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
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        return -1;
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    }
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    p->key_frame = 1;
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    l->bitbuf = 0;
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    l->bits = 0;
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    l->buf = buf + 8;
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    if (buf[2] >> 4 == 6)
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        l->shift = 2;
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    else {
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        l->shift = 8 - (buf[2] >> 4);
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        if (l->shift > 4) {
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            av_log(avctx, AV_LOG_ERROR, "Unknown WNV1 frame header value %i, please upload file for study\n", buf[2] >> 4);
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            l->shift = 4;
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        }
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        if (l->shift < 1) {
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            av_log(avctx, AV_LOG_ERROR, "Unknown WNV1 frame header value %i, please upload file for study\n", buf[2] >> 4);
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            l->shift = 1;
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        }
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    }
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    Y = p->data[0];
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    U = p->data[1];
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    V = p->data[2];
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    for (j = 0; j < avctx->height; j++) {
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        for (i = 0; i < avctx->width / 2; i++) {
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            Y[i * 2] = wnv1_get_code(l, prev_y);
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            prev_u = U[i] = wnv1_get_code(l, prev_u);
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            prev_y = Y[(i * 2) + 1] = wnv1_get_code(l, Y[i * 2]);
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            prev_v = V[i] = wnv1_get_code(l, prev_v);
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        }
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        Y += p->linesize[0];
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        U += p->linesize[1];
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        V += p->linesize[2];
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    }
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    *data_size = sizeof(AVFrame);
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    *(AVFrame*)data = l->pic;
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    return buf_size;
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}
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static int decode_init(AVCodecContext *avctx){
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    WNV1Context * const l = avctx->priv_data;
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    l->avctx = avctx;
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    avctx->pix_fmt = PIX_FMT_YUV422P;
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    return 0;
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}
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AVCodec wnv1_decoder = {
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    "wnv1",
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    CODEC_TYPE_VIDEO,
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    CODEC_ID_WNV1,
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    sizeof(WNV1Context),
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    decode_init,
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    NULL,
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    NULL,
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    decode_frame,
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    CODEC_CAP_DR1,
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};