jcinit.c

MPEG4解码源代码(包含完整的工程文件)

////////////////////////////////////////////////////////////////////////
//
//	Note : this file is included as part of the Smaller Animals Software
//	JpegFile package. Though this file has not been modified from it's 
//	original IJG 6a form, it is not the responsibility on the Independent
//	JPEG Group to answer questions regarding this code.
//	
//	Any questions you have about this code should be addressed to :
//
//	[e-mail]	- the distributor of this package.
//
//	Remember, by including this code in the JpegFile package, Smaller 
//	Animals Software assumes all responsibilities for answering questions
//	about it. If we (SA Software) can't answer your questions ourselves, we 
//	will direct you to people who can.
//
//	Thanks, CDL.
//
////////////////////////////////////////////////////////////////////////

/*
 * jcinit.c
 *
 * Copyright (C) 1991-1996, Thomas G. Lane.
 * This file is part of the Independent JPEG Group's software.
 * For conditions of distribution and use, see the accompanying README file.
 *
 * This file contains initialization logic for the JPEG compressor.
 * This routine is in charge of selecting the modules to be executed and
 * making an initialization call to each one.
 *
 * Logically, this code belongs in jcmaster.c.  It's split out because
 * linking this routine implies linking the entire compression library.
 * For a transcoding-only application, we want to be able to use jcmaster.c
 * without linking in the whole library.
 */

#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"


/*
 * Master selection of compression modules.
 * This is done once at the start of processing an image.  We determine
 * which modules will be used and give them appropriate initialization calls.
 */

GLOBAL(void)
jinit_compress_master (j_compress_ptr cinfo)
{
  /* Initialize master control (includes parameter checking/processing) */
  jinit_c_master_control(cinfo, FALSE /* full compression */);

  /* Preprocessing */
  if (! cinfo->raw_data_in) {
    jinit_color_converter(cinfo);
    jinit_downsampler(cinfo);
    jinit_c_prep_controller(cinfo, FALSE /* never need full buffer here */);
  }
  /* Forward DCT */
  jinit_forward_dct(cinfo);
  /* Entropy encoding: either Huffman or arithmetic coding. */
  if (cinfo->arith_code) {
    ERREXIT(cinfo, JERR_ARITH_NOTIMPL);
  } else {
    if (cinfo->progressive_mode) {
#ifdef C_PROGRESSIVE_SUPPORTED
      jinit_phuff_encoder(cinfo);
#else
      ERREXIT(cinfo, JERR_NOT_COMPILED);
#endif
    } else
      jinit_huff_encoder(cinfo);
  }

  /* Need a full-image coefficient buffer in any multi-pass mode. */
  jinit_c_coef_controller(cinfo,
			  (cinfo->num_scans > 1 || cinfo->optimize_coding));
  jinit_c_main_controller(cinfo, FALSE /* never need full buffer here */);

  jinit_marker_writer(cinfo);

  /* We can now tell the memory manager to allocate virtual arrays. */
  (*cinfo->mem->realize_virt_arrays) ((j_common_ptr) cinfo);

  /* Write the datastream header (SOI) immediately.
   * Frame and scan headers are postponed till later.
   * This lets application insert special markers after the SOI.
   */
  (*cinfo->marker->write_file_header) (cinfo);
}