lscrdec.c

Go to the documentation of this file.

/*
 * Copyright (c) 2019 Paul B Mahol
 *
 * 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 <stdint.h>
#include <zlib.h>
 
#include "libavutil/frame.h"
#include "libavutil/error.h"
#include "libavutil/log.h"
 
#include "avcodec.h"
#include "bytestream.h"
#include "codec.h"
#include "internal.h"
#include "packet.h"
#include "png.h"
#include "pngdsp.h"
 
typedef struct LSCRContext {
    PNGDSPContext   dsp;
    AVCodecContext *avctx;
 
    AVFrame        *last_picture;
    uint8_t        *buffer;
    int             buffer_size;
    uint8_t        *crow_buf;
    int             crow_size;
    uint8_t        *last_row;
    unsigned int    last_row_size;
 
    GetByteContext  gb;
    uint8_t        *image_buf;
    int             image_linesize;
    int             row_size;
    int             cur_h;
    int             y;
 
    z_stream        zstream;
} LSCRContext;
 
static void handle_row(LSCRContext *s)
{
    uint8_t *ptr, *last_row;
 
    ptr = s->image_buf + s->image_linesize * s->y;
    if (s->y == 0)
        last_row = s->last_row;
    else
        last_row = ptr - s->image_linesize;
 
    ff_png_filter_row(&s->dsp, ptr, s->crow_buf[0], s->crow_buf + 1,
                      last_row, s->row_size, 3);
 
    s->y++;
}
 
static int decode_idat(LSCRContext *s, int length)
{
    int ret;
    s->zstream.avail_in = FFMIN(length, bytestream2_get_bytes_left(&s->gb));
    s->zstream.next_in  = s->gb.buffer;
 
    if (length <= 0)
        return AVERROR_INVALIDDATA;
 
    bytestream2_skip(&s->gb, length);
 
    /* decode one line if possible */
    while (s->zstream.avail_in > 0) {
        ret = inflate(&s->zstream, Z_PARTIAL_FLUSH);
        if (ret != Z_OK && ret != Z_STREAM_END) {
            av_log(s->avctx, AV_LOG_ERROR, "inflate returned error %d\n", ret);
            return AVERROR_EXTERNAL;
        }
        if (s->zstream.avail_out == 0) {
            if (s->y < s->cur_h) {
                handle_row(s);
            }
            s->zstream.avail_out = s->crow_size;
            s->zstream.next_out  = s->crow_buf;
        }
        if (ret == Z_STREAM_END && s->zstream.avail_in > 0) {
            av_log(s->avctx, AV_LOG_WARNING,
                   "%d undecompressed bytes left in buffer\n", s->zstream.avail_in);
            return 0;
        }
    }
    return 0;
}
 
static int decode_frame_lscr(AVCodecContext *avctx,
                             void *data, int *got_frame,
                             AVPacket *avpkt)
{
    LSCRContext *const s = avctx->priv_data;
    GetByteContext *gb = &s->gb;
    AVFrame *frame = s->last_picture;
    int ret, nb_blocks, offset = 0;
 
    if (avpkt->size < 2)
        return AVERROR_INVALIDDATA;
    if (avpkt->size == 2)
        return 0;
 
    bytestream2_init(gb, avpkt->data, avpkt->size);
 
    nb_blocks = bytestream2_get_le16(gb);
    if (bytestream2_get_bytes_left(gb) < 2 + nb_blocks * (12 + 8))
        return AVERROR_INVALIDDATA;
 
    ret = ff_reget_buffer(avctx, frame,
                          nb_blocks ? 0 : FF_REGET_BUFFER_FLAG_READONLY);
    if (ret < 0)
        return ret;
 
    for (int b = 0; b < nb_blocks; b++) {
        int x, y, x2, y2, w, h, left;
        uint32_t csize, size;
 
        s->zstream.zalloc = ff_png_zalloc;
        s->zstream.zfree  = ff_png_zfree;
        s->zstream.opaque = NULL;
 
        if ((ret = inflateInit(&s->zstream)) != Z_OK) {
            av_log(avctx, AV_LOG_ERROR, "inflateInit returned error %d\n", ret);
            ret = AVERROR_EXTERNAL;
            goto end;
        }
 
        bytestream2_seek(gb, 2 + b * 12, SEEK_SET);
 
        x = bytestream2_get_le16(gb);
        y = bytestream2_get_le16(gb);
        x2 = bytestream2_get_le16(gb);
        y2 = bytestream2_get_le16(gb);
        w = x2-x;
        s->cur_h = h = y2-y;
 
        if (w <= 0 || x < 0 || x >= avctx->width || w + x > avctx->width ||
            h <= 0 || y < 0 || y >= avctx->height || h + y > avctx->height) {
            ret = AVERROR_INVALIDDATA;
            goto end;
        }
 
        size = bytestream2_get_le32(gb);
 
        frame->key_frame = (nb_blocks == 1) &&
                           (w == avctx->width) &&
                           (h == avctx->height) &&
                           (x == 0) && (y == 0);
 
        bytestream2_seek(gb, 2 + nb_blocks * 12 + offset, SEEK_SET);
        csize = bytestream2_get_be32(gb);
        if (bytestream2_get_le32(gb) != MKTAG('I', 'D', 'A', 'T')) {
            ret = AVERROR_INVALIDDATA;
            goto end;
        }
 
        offset += size;
        left = size;
 
        s->y                 = 0;
        s->row_size          = w * 3;
 
        av_fast_padded_malloc(&s->buffer, &s->buffer_size, s->row_size + 16);
        if (!s->buffer) {
            ret = AVERROR(ENOMEM);
            goto end;
        }
 
        av_fast_padded_malloc(&s->last_row, &s->last_row_size, s->row_size);
        if (!s->last_row) {
            ret = AVERROR(ENOMEM);
            goto end;
        }
 
        s->crow_size         = w * 3 + 1;
        s->crow_buf          = s->buffer + 15;
        s->zstream.avail_out = s->crow_size;
        s->zstream.next_out  = s->crow_buf;
        s->image_buf         = frame->data[0] + (avctx->height - y - 1) * frame->linesize[0] + x * 3;
        s->image_linesize    =-frame->linesize[0];
 
        while (left > 16) {
            ret = decode_idat(s, csize);
            if (ret < 0)
                goto end;
            left -= csize + 16;
            if (left > 16) {
                bytestream2_skip(gb, 4);
                csize = bytestream2_get_be32(gb);
                if (bytestream2_get_le32(gb) != MKTAG('I', 'D', 'A', 'T')) {
                    ret = AVERROR_INVALIDDATA;
                    goto end;
                }
            }
        }
 
        inflateEnd(&s->zstream);
    }
 
    frame->pict_type = frame->key_frame ? AV_PICTURE_TYPE_I : AV_PICTURE_TYPE_P;
 
    if ((ret = av_frame_ref(data, frame)) < 0)
        return ret;
 
    *got_frame = 1;
end:
    inflateEnd(&s->zstream);
 
    if (ret < 0)
        return ret;
    return avpkt->size;
}
 
static int lscr_decode_close(AVCodecContext *avctx)
{
    LSCRContext *s = avctx->priv_data;
 
    av_frame_free(&s->last_picture);
    av_freep(&s->buffer);
    av_freep(&s->last_row);
 
    return 0;
}
 
static int lscr_decode_init(AVCodecContext *avctx)
{
    LSCRContext *s = avctx->priv_data;
 
    avctx->color_range = AVCOL_RANGE_JPEG;
    avctx->pix_fmt     = AV_PIX_FMT_BGR24;
 
    s->avctx = avctx;
    s->last_picture = av_frame_alloc();
    if (!s->last_picture)
        return AVERROR(ENOMEM);
 
    ff_pngdsp_init(&s->dsp);
 
    return 0;
}
 
static void lscr_decode_flush(AVCodecContext *avctx)
{
    LSCRContext *s = avctx->priv_data;
    av_frame_unref(s->last_picture);
}
 
AVCodec ff_lscr_decoder = {
    .name           = "lscr",
    .long_name      = NULL_IF_CONFIG_SMALL("LEAD Screen Capture"),
    .type           = AVMEDIA_TYPE_VIDEO,
    .id             = AV_CODEC_ID_LSCR,
    .priv_data_size = sizeof(LSCRContext),
    .init           = lscr_decode_init,
    .close          = lscr_decode_close,
    .decode         = decode_frame_lscr,
    .flush          = lscr_decode_flush,
    .capabilities   = AV_CODEC_CAP_DR1,
    .caps_internal  = FF_CODEC_CAP_INIT_THREADSAFE,
};