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

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/*
 * Bethesda VID video decoder
 * Copyright (C) 2007 Nicholas Tung
 *
 * 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
 * @brief Bethesda Softworks VID Video Decoder
 * @author Nicholas Tung [ntung (at. ntung com] (2007-03)
 * @see http://wiki.multimedia.cx/index.php?title=Bethsoft_VID
 * @see http://www.svatopluk.com/andux/docs/dfvid.html
 */

#include "libavutil/common.h"
#include "avcodec.h"
#include "bethsoftvideo.h"
#include "bytestream.h"
#include "internal.h"

typedef struct BethsoftvidContext {
    AVFrame frame;
    GetByteContext g;
} BethsoftvidContext;

static av_cold int bethsoftvid_decode_init(AVCodecContext *avctx)
{
    BethsoftvidContext *vid = avctx->priv_data;
    avcodec_get_frame_defaults(&vid->frame);
    avctx->pix_fmt = AV_PIX_FMT_PAL8;
    return 0;
}

static int set_palette(BethsoftvidContext *ctx)
{
    uint32_t *palette = (uint32_t *)ctx->frame.data[1];
    int a;

    if (bytestream2_get_bytes_left(&ctx->g) < 256*3)
        return AVERROR_INVALIDDATA;

    for(a = 0; a < 256; a++){
        palette[a] = 0xFFU << 24 | bytestream2_get_be24u(&ctx->g) * 4;
        palette[a] |= palette[a] >> 6 & 0x30303;
    }
    ctx->frame.palette_has_changed = 1;
    return 0;
}

static int bethsoftvid_decode_frame(AVCodecContext *avctx,
                              void *data, int *got_frame,
                              AVPacket *avpkt)
{
    BethsoftvidContext * vid = avctx->priv_data;
    char block_type;
    uint8_t * dst;
    uint8_t * frame_end;
    int remaining = avctx->width;          // number of bytes remaining on a line
    int wrap_to_next_line;
    int code, ret;
    int yoffset;

    if ((ret = ff_reget_buffer(avctx, &vid->frame)) < 0)
        return ret;
    wrap_to_next_line = vid->frame.linesize[0] - avctx->width;

    if (avpkt->side_data_elems > 0 &&
        avpkt->side_data[0].type == AV_PKT_DATA_PALETTE) {
        bytestream2_init(&vid->g, avpkt->side_data[0].data,
                         avpkt->side_data[0].size);
        if ((ret = set_palette(vid)) < 0)
            return ret;
    }

    bytestream2_init(&vid->g, avpkt->data, avpkt->size);
    dst = vid->frame.data[0];
    frame_end = vid->frame.data[0] + vid->frame.linesize[0] * avctx->height;

    switch(block_type = bytestream2_get_byte(&vid->g)){
        case PALETTE_BLOCK: {
            *got_frame = 0;
            if ((ret = set_palette(vid)) < 0) {
                av_log(avctx, AV_LOG_ERROR, "error reading palette\n");
                return ret;
            }
            return bytestream2_tell(&vid->g);
        }
        case VIDEO_YOFF_P_FRAME:
            yoffset = bytestream2_get_le16(&vid->g);
            if(yoffset >= avctx->height)
                return AVERROR_INVALIDDATA;
            dst += vid->frame.linesize[0] * yoffset;
    }

    // main code
    while((code = bytestream2_get_byte(&vid->g))){
        int length = code & 0x7f;

        // copy any bytes starting at the current position, and ending at the frame width
        while(length > remaining){
            if(code < 0x80)
                bytestream2_get_buffer(&vid->g, dst, remaining);
            else if(block_type == VIDEO_I_FRAME)
                memset(dst, bytestream2_peek_byte(&vid->g), remaining);
            length -= remaining;      // decrement the number of bytes to be copied
            dst += remaining + wrap_to_next_line;    // skip over extra bytes at end of frame
            remaining = avctx->width;
            if(dst == frame_end)
                goto end;
        }

        // copy any remaining bytes after / if line overflows
        if(code < 0x80)
            bytestream2_get_buffer(&vid->g, dst, length);
        else if(block_type == VIDEO_I_FRAME)
            memset(dst, bytestream2_get_byte(&vid->g), length);
        remaining -= length;
        dst += length;
    }
    end:

    if ((ret = av_frame_ref(data, &vid->frame)) < 0)
        return ret;

    *got_frame = 1;

    return avpkt->size;
}

static av_cold int bethsoftvid_decode_end(AVCodecContext *avctx)
{
    BethsoftvidContext * vid = avctx->priv_data;
    av_frame_unref(&vid->frame);
    return 0;
}

AVCodec ff_bethsoftvid_decoder = {
    .name           = "bethsoftvid",
    .type           = AVMEDIA_TYPE_VIDEO,
    .id             = AV_CODEC_ID_BETHSOFTVID,
    .priv_data_size = sizeof(BethsoftvidContext),
    .init           = bethsoftvid_decode_init,
    .close          = bethsoftvid_decode_end,
    .decode         = bethsoftvid_decode_frame,
    .capabilities   = CODEC_CAP_DR1,
    .long_name      = NULL_IF_CONFIG_SMALL("Bethesda VID video"),
};