FFmpeg/libavcodec/wnv1.c

/*
 * Winnov WNV1 codec
 * Copyright (c) 2005 Konstantin Shishkov
 *
 * This library 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 of the License, or (at your option) any later version.
 *
 * This library 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 this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 */
 
/**
 * @file wnv1.c
 * Winnov WNV1 codec.
 */
 
#include "avcodec.h"
#include "common.h"


typedef struct WNV1Context{
    AVCodecContext *avctx;
    AVFrame pic;

    int shift;
    /* bit buffer */
    unsigned long bitbuf;
    int bits;
    uint8_t *buf;
} WNV1Context;

/* returns modified base_value */
static inline int wnv1_get_code(WNV1Context *w, int base_value)
{
    int v = 0;
            
    if (w->bits < 16) { /* need to fill bit buffer */
        w->bitbuf |= LE_16(w->buf) << w->bits;
        w->buf += 2;
        w->bits += 16;
    }

    /* escape code */
    if ((w->bitbuf & 0xFF) == 0xFF) {
        w->bitbuf >>= 8;
        w->bits -= 8;
        if (w->bits < 16) { /* need to fill bit buffer */
            w->bitbuf |= LE_16(w->buf) << w->bits;
            w->buf += 2;
            w->bits += 16;
        }
        v = w->bitbuf & (0xFF >> w->shift);
        w->bitbuf >>= 8 - w->shift;
        w->bits -= 8 - w->shift;
        return v << w->shift;
    }

    /* zero code */
    if (!(w->bitbuf & 1)) {
        w->bitbuf >>= 1;
        w->bits--;
        return base_value;
    }
    
    /* reversed unary code and sign */
    while (w->bits && w->bitbuf & 1) {
        w->bitbuf >>= 1;
        w->bits--;
        v++;
    }
    w->bitbuf >>= 1;
    w->bits--;
    if(w->bitbuf & 1)
        v = -v;
    w->bitbuf >>= 1;
    w->bits--;
    v <<= w->shift;
    return base_value + v;
}

static int decode_frame(AVCodecContext *avctx, 
                        void *data, int *data_size,
                        uint8_t *buf, int buf_size)
{
    WNV1Context * const l = avctx->priv_data;
    AVFrame * const p= (AVFrame*)&l->pic;
    unsigned char *Y,*U,*V;
    int i, j;
    int prev_y = 0, prev_u = 0, prev_v = 0;

    if(p->data[0])
        avctx->release_buffer(avctx, p);

    p->reference = 0;
    if(avctx->get_buffer(avctx, p) < 0){
        av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
        return -1;
    }
    p->key_frame = 1;
    
    l->bitbuf = 0;
    l->bits = 0;
    l->buf = buf + 8;
    
    if (buf[2] >> 4 == 6)
        l->shift = 2;
    else {
        l->shift = 8 - (buf[2] >> 4);
        if (l->shift > 4) {
            av_log(avctx, AV_LOG_ERROR, "Unknown WNV1 frame header value %i, please upload file for study\n", buf[2] >> 4);
            l->shift = 4;
        }
        if (l->shift < 1) {
            av_log(avctx, AV_LOG_ERROR, "Unknown WNV1 frame header value %i, please upload file for study\n", buf[2] >> 4);
            l->shift = 1;
        }
    }
    
    Y = p->data[0];
    U = p->data[1];
    V = p->data[2];
    for (j = 0; j < avctx->height; j++) {
        for (i = 0; i < avctx->width / 2; i++) {
            Y[i * 2] = wnv1_get_code(l, prev_y);
            prev_u = U[i] = wnv1_get_code(l, prev_u);
            prev_y = Y[(i * 2) + 1] = wnv1_get_code(l, Y[i * 2]);
            prev_v = V[i] = wnv1_get_code(l, prev_v);
        }
        Y += p->linesize[0];
        U += p->linesize[1];
        V += p->linesize[2];
    }

    
    *data_size = sizeof(AVFrame);
    *(AVFrame*)data = l->pic;
    
    return buf_size;
}

static int decode_init(AVCodecContext *avctx){
    WNV1Context * const l = avctx->priv_data;

    l->avctx = avctx;
    avctx->pix_fmt = PIX_FMT_YUV422P;

    return 0;
}

AVCodec wnv1_decoder = {
    "wnv1",
    CODEC_TYPE_VIDEO,
    CODEC_ID_WNV1,
    sizeof(WNV1Context),
    decode_init,
    NULL,
    NULL,
    decode_frame,
    CODEC_CAP_DR1,
};