qtrle.c

ffmpeg的完整源代码和作者自己写的文档。不但有在Linux的工程哦

/*
 * Quicktime Animation (RLE) Video Decoder
 * Copyright (C) 2004 the ffmpeg project
 *
 * 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 qtrle.c
 * QT RLE Video Decoder by Mike Melanson ([e-mail])
 * For more information about the QT RLE format, visit:
 *   http://www.pcisys.net/~melanson/codecs/
 *
 * The QT RLE decoder has seven modes of operation:
 * 1, 2, 4, 8, 16, 24, and 32 bits per pixel. For modes 1, 2, 4, and 8
 * the decoder outputs PAL8 colorspace data. 16-bit data yields RGB555
 * data. 24-bit data is RGB24 and 32-bit data is RGB32.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "avcodec.h"
#include "dsputil.h"

typedef struct QtrleContext {

    AVCodecContext *avctx;
    DSPContext dsp;
    AVFrame frame;

    unsigned char *buf;
    int size;

} QtrleContext;

#define CHECK_STREAM_PTR(n) \
  if ((stream_ptr + n) > s->size) { \
    av_log (s->avctx, AV_LOG_INFO, "Problem: stream_ptr out of bounds (%d >= %d)\n", \
      stream_ptr + n, s->size); \
    return; \
  }

#define CHECK_PIXEL_PTR(n) \
  if ((pixel_ptr + n > pixel_limit) || (pixel_ptr + n < 0)) { \
    av_log (s->avctx, AV_LOG_INFO, "Problem: pixel_ptr = %d, pixel_limit = %d\n", \
      pixel_ptr + n, pixel_limit); \
    return; \
  } \

static void qtrle_decode_1bpp(QtrleContext *s)
{
}

static void qtrle_decode_2bpp(QtrleContext *s)
{
}

static void qtrle_decode_4bpp(QtrleContext *s)
{
    int stream_ptr;
    int header;
    int start_line;
    int lines_to_change;
    int rle_code;
    int row_ptr, pixel_ptr;
    int row_inc = s->frame.linesize[0];
    unsigned char pi1, pi2, pi3, pi4, pi5, pi6, pi7, pi8;  /* 8 palette indices */
    unsigned char *rgb = s->frame.data[0];
    int pixel_limit = s->frame.linesize[0] * s->avctx->height;

    /* check if this frame is even supposed to change */
    if (s->size < 8)
        return;

    /* start after the chunk size */
    stream_ptr = 4;

    /* fetch the header */
    CHECK_STREAM_PTR(2);
    header = AV_RB16(&s->buf[stream_ptr]);
    stream_ptr += 2;

    /* if a header is present, fetch additional decoding parameters */
    if (header & 0x0008) {
        CHECK_STREAM_PTR(8);
        start_line = AV_RB16(&s->buf[stream_ptr]);
        stream_ptr += 4;
        lines_to_change = AV_RB16(&s->buf[stream_ptr]);
        stream_ptr += 4;
    } else {
        start_line = 0;
        lines_to_change = s->avctx->height;
    }

    row_ptr = row_inc * start_line;
    while (lines_to_change--) {
        CHECK_STREAM_PTR(2);
        pixel_ptr = row_ptr + (8 * (s->buf[stream_ptr++] - 1));

        while ((rle_code = (signed char)s->buf[stream_ptr++]) != -1) {
            if (rle_code == 0) {
                /* there's another skip code in the stream */
                CHECK_STREAM_PTR(1);
                pixel_ptr += (8 * (s->buf[stream_ptr++] - 1));
                CHECK_PIXEL_PTR(0);  /* make sure pixel_ptr is positive */
            } else if (rle_code < 0) {
                /* decode the run length code */
                rle_code = -rle_code;
                /* get the next 4 bytes from the stream, treat them as palette
                 * indices, and output them rle_code times */
                CHECK_STREAM_PTR(4);
                pi1 = ((s->buf[stream_ptr]) >> 4) & 0x0f;
                pi2 = (s->buf[stream_ptr++]) & 0x0f;
                pi3 = ((s->buf[stream_ptr]) >> 4) & 0x0f;
                pi4 = (s->buf[stream_ptr++]) & 0x0f;
                pi5 = ((s->buf[stream_ptr]) >> 4) & 0x0f;
                pi6 = (s->buf[stream_ptr++]) & 0x0f;
                pi7 = ((s->buf[stream_ptr]) >> 4) & 0x0f;
                pi8 = (s->buf[stream_ptr++]) & 0x0f;

                CHECK_PIXEL_PTR(rle_code * 8);

                while (rle_code--) {
                    rgb[pixel_ptr++] = pi1;
                    rgb[pixel_ptr++] = pi2;
                    rgb[pixel_ptr++] = pi3;
                    rgb[pixel_ptr++] = pi4;
                    rgb[pixel_ptr++] = pi5;
                    rgb[pixel_ptr++] = pi6;
                    rgb[pixel_ptr++] = pi7;
                    rgb[pixel_ptr++] = pi8;
                }
            } else {
                /* copy the same pixel directly to output 4 times */
                rle_code *= 4;
                CHECK_STREAM_PTR(rle_code);
                CHECK_PIXEL_PTR(rle_code*2);

                while (rle_code--) {
                    rgb[pixel_ptr++] = ((s->buf[stream_ptr]) >> 4) & 0x0f;
                    rgb[pixel_ptr++] = (s->buf[stream_ptr++]) & 0x0f;
                }
            }
        }
        row_ptr += row_inc;
    }
}

static void qtrle_decode_8bpp(QtrleContext *s)
{
    int stream_ptr;
    int header;
    int start_line;
    int lines_to_change;
    int rle_code;
    int row_ptr, pixel_ptr;
    int row_inc = s->frame.linesize[0];
    unsigned char pi1, pi2, pi3, pi4;  /* 4 palette indices */
    unsigned char *rgb = s->frame.data[0];
    int pixel_limit = s->frame.linesize[0] * s->avctx->height;

    /* check if this frame is even supposed to change */
    if (s->size < 8)
        return;

    /* start after the chunk size */
    stream_ptr = 4;

    /* fetch the header */
    CHECK_STREAM_PTR(2);
    header = AV_RB16(&s->buf[stream_ptr]);
    stream_ptr += 2;

    /* if a header is present, fetch additional decoding parameters */
    if (header & 0x0008) {
        CHECK_STREAM_PTR(8);
        start_line = AV_RB16(&s->buf[stream_ptr]);
        stream_ptr += 4;
        lines_to_change = AV_RB16(&s->buf[stream_ptr]);
        stream_ptr += 4;
    } else {
        start_line = 0;
        lines_to_change = s->avctx->height;
    }

    row_ptr = row_inc * start_line;
    while (lines_to_change--) {
        CHECK_STREAM_PTR(2);
        pixel_ptr = row_ptr + (4 * (s->buf[stream_ptr++] - 1));

        while ((rle_code = (signed char)s->buf[stream_ptr++]) != -1) {
            if (rle_code == 0) {
                /* there's another skip code in the stream */
                CHECK_STREAM_PTR(1);
                pixel_ptr += (4 * (s->buf[stream_ptr++] - 1));
                CHECK_PIXEL_PTR(0);  /* make sure pixel_ptr is positive */
            } else if (rle_code < 0) {
                /* decode the run length code */
                rle_code = -rle_code;
                /* get the next 4 bytes from the stream, treat them as palette
                 * indices, and output them rle_code times */
                CHECK_STREAM_PTR(4);
                pi1 = s->buf[stream_ptr++];
                pi2 = s->buf[stream_ptr++];
                pi3 = s->buf[stream_ptr++];
                pi4 = s->buf[stream_ptr++];

                CHECK_PIXEL_PTR(rle_code * 4);

                while (rle_code--) {
                    rgb[pixel_ptr++] = pi1;
                    rgb[pixel_ptr++] = pi2;
                    rgb[pixel_ptr++] = pi3;
                    rgb[pixel_ptr++] = pi4;
                }
            } else {
                /* copy the same pixel directly to output 4 times */
                rle_code *= 4;
                CHECK_STREAM_PTR(rle_code);
                CHECK_PIXEL_PTR(rle_code);

                while (rle_code--) {
                    rgb[pixel_ptr++] = s->buf[stream_ptr++];
                }
            }
        }
        row_ptr += row_inc;
    }
}

static void qtrle_decode_16bpp(QtrleContext *s)
{
    int stream_ptr;
    int header;
    int start_line;
    int lines_to_change;
    int rle_code;
    int row_ptr, pixel_ptr;
    int row_inc = s->frame.linesize[0];
    unsigned short rgb16;
    unsigned char *rgb = s->frame.data[0];
    int pixel_limit = s->frame.linesize[0] * s->avctx->height;

    /* check if this frame is even supposed to change */
    if (s->size < 8)
        return;

    /* start after the chunk size */
    stream_ptr = 4;

    /* fetch the header */
    CHECK_STREAM_PTR(2);
    header = AV_RB16(&s->buf[stream_ptr]);
    stream_ptr += 2;

    /* if a header is present, fetch additional decoding parameters */
    if (header & 0x0008) {
        CHECK_STREAM_PTR(8);
        start_line = AV_RB16(&s->buf[stream_ptr]);
        stream_ptr += 4;
        lines_to_change = AV_RB16(&s->buf[stream_ptr]);
        stream_ptr += 4;
    } else {
        start_line = 0;
        lines_to_change = s->avctx->height;
    }

    row_ptr = row_inc * start_line;
    while (lines_to_change--) {
        CHECK_STREAM_PTR(2);
        pixel_ptr = row_ptr + (s->buf[stream_ptr++] - 1) * 2;

        while ((rle_code = (signed char)s->buf[stream_ptr++]) != -1) {
            if (rle_code == 0) {
                /* there's another skip code in the stream */
                CHECK_STREAM_PTR(1);
                pixel_ptr += (s->buf[stream_ptr++] - 1) * 2;
                CHECK_PIXEL_PTR(0);  /* make sure pixel_ptr is positive */
            } else if (rle_code < 0) {
                /* decode the run length code */
                rle_code = -rle_code;
                CHECK_STREAM_PTR(2);
                rgb16 = AV_RB16(&s->buf[stream_ptr]);
                stream_ptr += 2;

                CHECK_PIXEL_PTR(rle_code * 2);

                while (rle_code--) {
                    *(unsigned short *)(&rgb[pixel_ptr]) = rgb16;
                    pixel_ptr += 2;
                }
            } else {
                CHECK_STREAM_PTR(rle_code * 2);
                CHECK_PIXEL_PTR(rle_code * 2);

                /* copy pixels directly to output */
                while (rle_code--) {