aliaspixdec.c

/*
 * Alias PIX image decoder
 * Copyright (C) 2014 Vittorio Giovara <vittorio.giovara@gmail.com>
 *
 * 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
 */

#include "libavutil/intreadwrite.h"

#include "avcodec.h"
#include "bytestream.h"
#include "internal.h"

#define ALIAS_HEADER_SIZE 10

static int decode_frame(AVCodecContext *avctx, void *data, int *got_frame,
                        AVPacket *avpkt)
{
    AVFrame *f = data;
    GetByteContext gb;
    int width, height, ret, bits_pixel, pixel;
    uint8_t *out_buf;
    uint8_t count;
    int x, y;

    bytestream2_init(&gb, avpkt->data, avpkt->size);

    if (bytestream2_get_bytes_left(&gb) < ALIAS_HEADER_SIZE) {
        av_log(avctx, AV_LOG_ERROR, "Header too small %d.\n", avpkt->size);
        return AVERROR_INVALIDDATA;
    }

    width  = bytestream2_get_be16u(&gb);
    height = bytestream2_get_be16u(&gb);
    bytestream2_skipu(&gb, 4); // obsolete X, Y offset
    bits_pixel = bytestream2_get_be16u(&gb);

    if (bits_pixel == 24)
        avctx->pix_fmt = AV_PIX_FMT_BGR24;
    else if (bits_pixel == 8)
        avctx->pix_fmt = AV_PIX_FMT_GRAY8;
    else {
        av_log(avctx, AV_LOG_ERROR, "Invalid pixel format.\n");
        return AVERROR_INVALIDDATA;
    }

    ret = ff_set_dimensions(avctx, width, height);
    if (ret < 0)
        return ret;

    if (bytestream2_get_bytes_left(&gb) < width*height / 255)
        return AVERROR_INVALIDDATA;

    ret = ff_get_buffer(avctx, f, 0);
    if (ret < 0)
        return ret;

    f->pict_type = AV_PICTURE_TYPE_I;
    f->key_frame = 1;

    x = 0;
    y = 1;
    out_buf = f->data[0];
    while (bytestream2_get_bytes_left(&gb) > 0) {
        int i;

        /* set buffer at the right position at every new line */
        if (x == avctx->width) {
            x = 0;
            out_buf = f->data[0] + f->linesize[0] * y++;
            if (y > avctx->height) {
                av_log(avctx, AV_LOG_ERROR,
                       "Ended frame decoding with %d bytes left.\n",
                       bytestream2_get_bytes_left(&gb));
                return AVERROR_INVALIDDATA;
            }
        }

        /* read packet and copy data */
        count = bytestream2_get_byteu(&gb);
        if (!count || x + count > avctx->width) {
            av_log(avctx, AV_LOG_ERROR, "Invalid run length %d.\n", count);
            return AVERROR_INVALIDDATA;
        }

        if (avctx->pix_fmt == AV_PIX_FMT_BGR24) {
            pixel = bytestream2_get_be24(&gb);
            for (i = 0; i < count; i++) {
                AV_WB24(out_buf, pixel);
                out_buf += 3;
            }
        } else { // AV_PIX_FMT_GRAY8
            pixel = bytestream2_get_byte(&gb);
            for (i = 0; i < count; i++)
                *out_buf++ = pixel;
        }

        x += i;
    }

    if (x != width || y != height) {
        av_log(avctx, AV_LOG_ERROR, "Picture stopped at %d,%d.\n", x, y);
        return AVERROR_INVALIDDATA;
    }

    *got_frame = 1;
    return avpkt->size;
}

AVCodec ff_alias_pix_decoder = {
    .name         = "alias_pix",
    .long_name    = NULL_IF_CONFIG_SMALL("Alias/Wavefront PIX image"),
    .type         = AVMEDIA_TYPE_VIDEO,
    .id           = AV_CODEC_ID_ALIAS_PIX,
    .decode       = decode_frame,
    .capabilities = AV_CODEC_CAP_DR1,
};