annotate ffmpeg/libavcodec/wnv1.c @ 13:844d341cf643 tip

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/*
 * Winnov WNV1 codec
 * Copyright (c) 2005 Konstantin Shishkov
 *
 * 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
 * Winnov WNV1 codec.
 */

#include "avcodec.h"
#include "get_bits.h"
#include "internal.h"
#include "mathops.h"


typedef struct WNV1Context {
    AVCodecContext *avctx;

    int shift;
    GetBitContext gb;
} WNV1Context;

static const uint16_t code_tab[16][2] = {
    { 0x1FD, 9 }, { 0xFD, 8 }, { 0x7D, 7 }, { 0x3D, 6 }, { 0x1D, 5 }, { 0x0D, 4 }, { 0x005, 3 },
    { 0x000, 1 },
    { 0x004, 3 }, { 0x0C, 4 }, { 0x1C, 5 }, { 0x3C, 6 }, { 0x7C, 7 }, { 0xFC, 8 }, { 0x1FC, 9 }, { 0xFF, 8 }
};

#define CODE_VLC_BITS 9
static VLC code_vlc;

/* returns modified base_value */
static inline int wnv1_get_code(WNV1Context *w, int base_value)
{
    int v = get_vlc2(&w->gb, code_vlc.table, CODE_VLC_BITS, 1);

    if (v == 15)
        return ff_reverse[get_bits(&w->gb, 8 - w->shift)];
    else
        return base_value + ((v - 7) << w->shift);
}

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

    if(buf_size<=8) {
        av_log(avctx, AV_LOG_ERROR, "buf_size %d is too small\n", buf_size);
        return AVERROR_INVALIDDATA;
    }

    rbuf = av_malloc(buf_size + FF_INPUT_BUFFER_PADDING_SIZE);
    if (!rbuf) {
        av_log(avctx, AV_LOG_ERROR, "Cannot allocate temporary buffer\n");
        return AVERROR(ENOMEM);
    }

    if ((ret = ff_get_buffer(avctx, p, 0)) < 0) {
        av_free(rbuf);
        return ret;
    }
    p->key_frame = 1;

    for (i = 8; i < buf_size; i++)
        rbuf[i] = ff_reverse[buf[i]];
    init_get_bits(&l->gb, rbuf + 8, (buf_size - 8) * 8);

    if (buf[2] >> 4 == 6)
        l->shift = 2;
    else {
        l->shift = 8 - (buf[2] >> 4);
        if (l->shift > 4) {
            avpriv_request_sample(avctx,
                                  "Unknown WNV1 frame header value %i",
                                  buf[2] >> 4);
            l->shift = 4;
        }
        if (l->shift < 1) {
            avpriv_request_sample(avctx,
                                  "Unknown WNV1 frame header value %i",
                                  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];
    }


    *got_frame      = 1;
    av_free(rbuf);

    return buf_size;
}

static av_cold int decode_init(AVCodecContext *avctx)
{
    WNV1Context * const l = avctx->priv_data;
    static VLC_TYPE code_table[1 << CODE_VLC_BITS][2];

    l->avctx       = avctx;
    avctx->pix_fmt = AV_PIX_FMT_YUV422P;

    code_vlc.table           = code_table;
    code_vlc.table_allocated = 1 << CODE_VLC_BITS;
    init_vlc(&code_vlc, CODE_VLC_BITS, 16,
             &code_tab[0][1], 4, 2,
             &code_tab[0][0], 4, 2, INIT_VLC_USE_NEW_STATIC);

    return 0;
}

AVCodec ff_wnv1_decoder = {
    .name           = "wnv1",
    .type           = AVMEDIA_TYPE_VIDEO,
    .id             = AV_CODEC_ID_WNV1,
    .priv_data_size = sizeof(WNV1Context),
    .init           = decode_init,
    .decode         = decode_frame,
    .capabilities   = CODEC_CAP_DR1,
    .long_name      = NULL_IF_CONFIG_SMALL("Winnov WNV1"),
};