smc.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 Graphics (SMC) Video Decoder
 * Copyright (C) 2003 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 smc.c
 * QT SMC Video Decoder by Mike Melanson ([e-mail])
 * For more information about the SMC format, visit:
 *   http://www.pcisys.net/~melanson/codecs/
 *
 * The SMC decoder outputs PAL8 colorspace data.
 */

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

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

#define CPAIR 2
#define CQUAD 4
#define COCTET 8

#define COLORS_PER_TABLE 256

typedef struct SmcContext {

    AVCodecContext *avctx;
    DSPContext dsp;
    AVFrame frame;

    unsigned char *buf;
    int size;

    /* SMC color tables */
    unsigned char color_pairs[COLORS_PER_TABLE * CPAIR];
    unsigned char color_quads[COLORS_PER_TABLE * CQUAD];
    unsigned char color_octets[COLORS_PER_TABLE * COCTET];

} SmcContext;

#define GET_BLOCK_COUNT() \
  (opcode & 0x10) ? (1 + s->buf[stream_ptr++]) : 1 + (opcode & 0x0F);

#define ADVANCE_BLOCK() \
{ \
    pixel_ptr += 4; \
    if (pixel_ptr >= width) \
    { \
        pixel_ptr = 0; \
        row_ptr += stride * 4; \
    } \
    total_blocks--; \
    if (total_blocks < 0) \
    { \
        av_log(s->avctx, AV_LOG_INFO, "warning: block counter just went negative (this should not happen)\n"); \
        return; \
    } \
}

static void smc_decode_stream(SmcContext *s)
{
    int width = s->avctx->width;
    int height = s->avctx->height;
    int stride = s->frame.linesize[0];
    int i;
    int stream_ptr = 0;
    int chunk_size;
    unsigned char opcode;
    int n_blocks;
    unsigned int color_flags;
    unsigned int color_flags_a;
    unsigned int color_flags_b;
    unsigned int flag_mask;

    unsigned char *pixels = s->frame.data[0];

    int image_size = height * s->frame.linesize[0];
    int row_ptr = 0;
    int pixel_ptr = 0;
    int pixel_x, pixel_y;
    int row_inc = stride - 4;
    int block_ptr;
    int prev_block_ptr;
    int prev_block_ptr1, prev_block_ptr2;
    int prev_block_flag;
    int total_blocks;
    int color_table_index;  /* indexes to color pair, quad, or octet tables */
    int pixel;

    int color_pair_index = 0;
    int color_quad_index = 0;
    int color_octet_index = 0;

    /* make the palette available */
    memcpy(s->frame.data[1], s->avctx->palctrl->palette, AVPALETTE_SIZE);
    if (s->avctx->palctrl->palette_changed) {
        s->frame.palette_has_changed = 1;
        s->avctx->palctrl->palette_changed = 0;
    }

    chunk_size = AV_RB32(&s->buf[stream_ptr]) & 0x00FFFFFF;
    stream_ptr += 4;
    if (chunk_size != s->size)
        av_log(s->avctx, AV_LOG_INFO, "warning: MOV chunk size != encoded chunk size (%d != %d); using MOV chunk size\n",
            chunk_size, s->size);

    chunk_size = s->size;
    total_blocks = ((s->avctx->width + 3) / 4) * ((s->avctx->height + 3) / 4);

    /* traverse through the blocks */
    while (total_blocks) {
        /* sanity checks */
        /* make sure stream ptr hasn't gone out of bounds */
        if (stream_ptr > chunk_size) {
            av_log(s->avctx, AV_LOG_INFO, "SMC decoder just went out of bounds (stream ptr = %d, chunk size = %d)\n",
                stream_ptr, chunk_size);
            return;
        }
        /* make sure the row pointer hasn't gone wild */
        if (row_ptr >= image_size) {
            av_log(s->avctx, AV_LOG_INFO, "SMC decoder just went out of bounds (row ptr = %d, height = %d)\n",
                row_ptr, image_size);
            return;
        }

        opcode = s->buf[stream_ptr++];
        switch (opcode & 0xF0) {
        /* skip n blocks */
        case 0x00:
        case 0x10:
            n_blocks = GET_BLOCK_COUNT();
            while (n_blocks--) {
                ADVANCE_BLOCK();
            }
            break;

        /* repeat last block n times */
        case 0x20:
        case 0x30:
            n_blocks = GET_BLOCK_COUNT();

            /* sanity check */
            if ((row_ptr == 0) && (pixel_ptr == 0)) {
                av_log(s->avctx, AV_LOG_INFO, "encountered repeat block opcode (%02X) but no blocks rendered yet\n",
                    opcode & 0xF0);
                break;
            }

            /* figure out where the previous block started */
            if (pixel_ptr == 0)
                prev_block_ptr1 =
                    (row_ptr - s->avctx->width * 4) + s->avctx->width - 4;
            else
                prev_block_ptr1 = row_ptr + pixel_ptr - 4;

            while (n_blocks--) {
                block_ptr = row_ptr + pixel_ptr;
                prev_block_ptr = prev_block_ptr1;
                for (pixel_y = 0; pixel_y < 4; pixel_y++) {
                    for (pixel_x = 0; pixel_x < 4; pixel_x++) {
                        pixels[block_ptr++] = pixels[prev_block_ptr++];
                    }
                    block_ptr += row_inc;
                    prev_block_ptr += row_inc;
                }
                ADVANCE_BLOCK();
            }
            break;

        /* repeat previous pair of blocks n times */
        case 0x40:
        case 0x50:
            n_blocks = GET_BLOCK_COUNT();
            n_blocks *= 2;

            /* sanity check */
            if ((row_ptr == 0) && (pixel_ptr < 2 * 4)) {
                av_log(s->avctx, AV_LOG_INFO, "encountered repeat block opcode (%02X) but not enough blocks rendered yet\n",
                    opcode & 0xF0);
                break;
            }

            /* figure out where the previous 2 blocks started */
            if (pixel_ptr == 0)
                prev_block_ptr1 = (row_ptr - s->avctx->width * 4) +
                    s->avctx->width - 4 * 2;
            else if (pixel_ptr == 4)
                prev_block_ptr1 = (row_ptr - s->avctx->width * 4) + row_inc;
            else
                prev_block_ptr1 = row_ptr + pixel_ptr - 4 * 2;

            if (pixel_ptr == 0)
                prev_block_ptr2 = (row_ptr - s->avctx->width * 4) + row_inc;
            else
                prev_block_ptr2 = row_ptr + pixel_ptr - 4;

            prev_block_flag = 0;
            while (n_blocks--) {
                block_ptr = row_ptr + pixel_ptr;
                if (prev_block_flag)
                    prev_block_ptr = prev_block_ptr2;
                else
                    prev_block_ptr = prev_block_ptr1;
                prev_block_flag = !prev_block_flag;

                for (pixel_y = 0; pixel_y < 4; pixel_y++) {
                    for (pixel_x = 0; pixel_x < 4; pixel_x++) {
                        pixels[block_ptr++] = pixels[prev_block_ptr++];
                    }
                    block_ptr += row_inc;
                    prev_block_ptr += row_inc;
                }
                ADVANCE_BLOCK();
            }
            break;

        /* 1-color block encoding */
        case 0x60:
        case 0x70:
            n_blocks = GET_BLOCK_COUNT();
            pixel = s->buf[stream_ptr++];

            while (n_blocks--) {
                block_ptr = row_ptr + pixel_ptr;
                for (pixel_y = 0; pixel_y < 4; pixel_y++) {
                    for (pixel_x = 0; pixel_x < 4; pixel_x++) {