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/*

 * jdcoefct.c

 *

 * Copyright (C) 1994-1997, 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 the coefficient buffer controller for decompression.

 * This controller is the top level of the JPEG decompressor proper.

 * The coefficient buffer lies between entropy decoding and inverse-DCT steps.

 *

 * In buffered-image mode, this controller is the interface between

 * input-oriented processing and output-oriented processing.

 * Also, the input side (only) is used when reading a file for transcoding.

 */

#define JPEG_INTERNALS

#include "jinclude.h"

#include "jpeglib.h"

/* Block smoothing is only applicable for progressive JPEG, so: */

#ifndef D_PROGRESSIVE_SUPPORTED

#undef BLOCK_SMOOTHING_SUPPORTED

#endif

/* Private buffer controller object */

typedef struct {

  struct jpeg_d_coef_controller pub; /* public fields */

  /* These variables keep track of the current location of the input side. */

  /* cinfo->input_iMCU_row is also used for this. */

  JDIMENSION MCU_ctr;           /* counts MCUs processed in current row */

  int MCU_vert_offset;          /* counts MCU rows within iMCU row */

  int MCU_rows_per_iMCU_row;    /* number of such rows needed */

  /* The output side's location is represented by cinfo->output_iMCU_row. */

  /* In single-pass modes, it's sufficient to buffer just one MCU.

   * We allocate a workspace of D_MAX_BLOCKS_IN_MCU coefficient blocks,

   * and let the entropy decoder write into that workspace each time.

   * (On 80x86, the workspace is FAR even though it's not really very big;

   * this is to keep the module interfaces unchanged when a large coefficient

   * buffer is necessary.)

   * In multi-pass modes, this array points to the current MCU's blocks

   * within the virtual arrays; it is used only by the input side.

   */

  JBLOCKROW MCU_buffer[D_MAX_BLOCKS_IN_MCU];

#ifdef D_MULTISCAN_FILES_SUPPORTED

  /* In multi-pass modes, we need a virtual block array for each component. */

  jvirt_barray_ptr whole_image[MAX_COMPONENTS];

#endif

#ifdef BLOCK_SMOOTHING_SUPPORTED

  /* When doing block smoothing, we latch coefficient Al values here */

  int * coef_bits_latch;

#define SAVED_COEFS  6          /* we save coef_bits[0..5] */

#endif

} my_coef_controller;

typedef my_coef_controller * my_coef_ptr;

/* Forward declarations */

METHODDEF(int) decompress_onepass

        JPP((j_decompress_ptr cinfo, JSAMPIMAGE output_buf));

#ifdef D_MULTISCAN_FILES_SUPPORTED

METHODDEF(int) decompress_data

        JPP((j_decompress_ptr cinfo, JSAMPIMAGE output_buf));

#endif

#ifdef BLOCK_SMOOTHING_SUPPORTED

LOCAL(boolean) smoothing_ok JPP((j_decompress_ptr cinfo));

METHODDEF(int) decompress_smooth_data

        JPP((j_decompress_ptr cinfo, JSAMPIMAGE output_buf));

#endif

LOCAL(void)

start_iMCU_row (j_decompress_ptr cinfo)

/* Reset within-iMCU-row counters for a new row (input side) */

{

  my_coef_ptr coef = (my_coef_ptr) cinfo->coef;

  /* In an interleaved scan, an MCU row is the same as an iMCU row.

   * In a noninterleaved scan, an iMCU row has v_samp_factor MCU rows.

   * But at the bottom of the image, process only what's left.

   */

  if (cinfo->comps_in_scan > 1) {

    coef->MCU_rows_per_iMCU_row = 1;

  } else {

    if (cinfo->input_iMCU_row < (cinfo->total_iMCU_rows-1))

      coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->v_samp_factor;

    else

      coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->last_row_height;

  }

  coef->MCU_ctr = 0;

  coef->MCU_vert_offset = 0;

}

/*

 * Initialize for an input processing pass.

 */

METHODDEF(void)

start_input_pass (j_decompress_ptr cinfo)

{

  cinfo->input_iMCU_row = 0;

  start_iMCU_row(cinfo);

}

/*

 * Initialize for an output processing pass.

 */

METHODDEF(void)

start_output_pass (j_decompress_ptr cinfo)

{

#ifdef BLOCK_SMOOTHING_SUPPORTED

  my_coef_ptr coef = (my_coef_ptr) cinfo->coef;

  /* If multipass, check to see whether to use block smoothing on this pass */

  if (coef->pub.coef_arrays != NULL) {

    if (cinfo->do_block_smoothing && smoothing_ok(cinfo))

      coef->pub.decompress_data = decompress_smooth_data;

    else

      coef->pub.decompress_data = decompress_data;

  }

#endif

  cinfo->output_iMCU_row = 0;

}

/*

 * Decompress and return some data in the single-pass case.

 * Always attempts to emit one fully interleaved MCU row ("iMCU" row).

 * Input and output must run in lockstep since we have only a one-MCU buffer.

 * Return value is JPEG_ROW_COMPLETED, JPEG_SCAN_COMPLETED, or JPEG_SUSPENDED.

 *

 * NB: output_buf contains a plane for each component in image,

 * which we index according to the component's SOF position.

 */

METHODDEF(int)

decompress_onepass (j_decompress_ptr cinfo, JSAMPIMAGE output_buf)

{

  my_coef_ptr coef = (my_coef_ptr) cinfo->coef;

  JDIMENSION MCU_col_num;       /* index of current MCU within row */

  JDIMENSION last_MCU_col = cinfo->MCUs_per_row - 1;

  JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;

  int blkn, ci, xindex, yindex, yoffset, useful_width;

  JSAMPARRAY output_ptr;

  JDIMENSION start_col, output_col;

  jpeg_component_info *compptr;

  inverse_DCT_method_ptr inverse_DCT;

  /* Loop to process as much as one whole iMCU row */

  for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;

       yoffset++) {

    for (MCU_col_num = coef->MCU_ctr; MCU_col_num <= last_MCU_col;

         MCU_col_num++) {

      /* Try to fetch an MCU.  Entropy decoder expects buffer to be zeroed. */

      jzero_far((void FAR *) coef->MCU_buffer[0],

                (size_t) (cinfo->blocks_in_MCU * SIZEOF(JBLOCK)));

      if (! (*cinfo->entropy->decode_mcu) (cinfo, coef->MCU_buffer)) {

        /* Suspension forced; update state counters and exit */

        coef->MCU_vert_offset = yoffset;

        coef->MCU_ctr = MCU_col_num;

        return JPEG_SUSPENDED;

      }

      /* Determine where data should go in output_buf and do the IDCT thing.

       * We skip dummy blocks at the right and bottom edges (but blkn gets

       * incremented past them!).  Note the inner loop relies on having

       * allocated the MCU_buffer[] blocks sequentially.

       */

      blkn = 0;                  /* index of current DCT block within MCU */

      for (ci = 0; ci < cinfo->comps_in_scan; ci++) {

        compptr = cinfo->cur_comp_info[ci];

        /* Don't bother to IDCT an uninteresting component. */

        if (! compptr->component_needed) {

          blkn += compptr->MCU_blocks;

          continue;

        }

        inverse_DCT = cinfo->idct->inverse_DCT[compptr->component_index];

        useful_width = (MCU_col_num < last_MCU_col) ? compptr->MCU_width

                                                    : compptr->last_col_width;

        output_ptr = output_buf[compptr->component_index] +

          yoffset * compptr->DCT_scaled_size;

        start_col = MCU_col_num * compptr->MCU_sample_width;

        for (yindex = 0; yindex < compptr->MCU_height; yindex++) {

          if (cinfo->input_iMCU_row < last_iMCU_row ||

              yoffset+yindex < compptr->last_row_height) {

            output_col = start_col;

            for (xindex = 0; xindex < useful_width; xindex++) {

              (*inverse_DCT) (cinfo, compptr,

                              (JCOEFPTR) coef->MCU_buffer[blkn+xindex],

                              output_ptr, output_col);

              output_col += compptr->DCT_scaled_size;

            }

          }

          blkn += compptr->MCU_width;

          output_ptr += compptr->DCT_scaled_size;

        }

      }

    }

    /* Completed an MCU row, but perhaps not an iMCU row */

    coef->MCU_ctr = 0;

  }

  /* Completed the iMCU row, advance counters for next one */

  cinfo->output_iMCU_row++;

  if (++(cinfo->input_iMCU_row) < cinfo->total_iMCU_rows) {

    start_iMCU_row(cinfo);

    return JPEG_ROW_COMPLETED;

  }

  /* Completed the scan */

  (*cinfo->inputctl->finish_input_pass) (cinfo);

  return JPEG_SCAN_COMPLETED;

}

/*

 * Dummy consume-input routine for single-pass operation.

 */

METHODDEF(int)

dummy_consume_data (j_decompress_ptr cinfo)

{

  return JPEG_SUSPENDED;        /* Always indicate nothing was done */

}

#ifdef D_MULTISCAN_FILES_SUPPORTED

/*

 * Consume input data and store it in the full-image coefficient buffer.

 * We read as much as one fully interleaved MCU row ("iMCU" row) per call,

 * ie, v_samp_factor block rows for each component in the scan.

 * Return value is JPEG_ROW_COMPLETED, JPEG_SCAN_COMPLETED, or JPEG_SUSPENDED.

 */

METHODDEF(int)

consume_data (j_decompress_ptr cinfo)

{

  my_coef_ptr coef = (my_coef_ptr) cinfo->coef;

  JDIMENSION MCU_col_num;       /* index of current MCU within row */

  int blkn, ci, xindex, yindex, yoffset;

  JDIMENSION start_col;

  JBLOCKARRAY buffer[MAX_COMPS_IN_SCAN];

  JBLOCKROW buffer_ptr;

  jpeg_component_info *compptr;

  /* Align the virtual buffers for the components used in this scan. */

  for (ci = 0; ci < cinfo->comps_in_scan; ci++) {

    compptr = cinfo->cur_comp_info[ci];

    buffer[ci] = (*cinfo->mem->access_virt_barray)

      ((j_common_ptr) cinfo, coef->whole_image[compptr->component_index],

       cinfo->input_iMCU_row * compptr->v_samp_factor,

       (JDIMENSION) compptr->v_samp_factor, TRUE);

    /* Note: entropy decoder expects buffer to be zeroed,

     * but this is handled automatically by the memory manager

     * because we requested a pre-zeroed array.

     */

  }

  /* Loop to process one whole iMCU row */

  for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;

       yoffset++) {

    for (MCU_col_num = coef->MCU_ctr; MCU_col_num < cinfo->MCUs_per_row;

         MCU_col_num++) {

      /* Construct list of pointers to DCT blocks belonging to this MCU */

      blkn = 0;                  /* index of current DCT block within MCU */

      for (ci = 0; ci < cinfo->comps_in_scan; ci++) {

        compptr = cinfo->cur_comp_info[ci];

        start_col = MCU_col_num * compptr->MCU_width;

        for (yindex = 0; yindex < compptr->MCU_height; yindex++) {

          buffer_ptr = buffer[ci][yindex+yoffset] + start_col;

          for (xindex = 0; xindex < compptr->MCU_width; xindex++) {

            coef->MCU_buffer[blkn++] = buffer_ptr++;

          }

        }

      }

      /* Try to fetch the MCU. */

      if (! (*cinfo->entropy->decode_mcu) (cinfo, coef->MCU_buffer)) {

        /* Suspension forced; update state counters and exit */

        coef->MCU_vert_offset = yoffset;

        coef->MCU_ctr = MCU_col_num;

        return JPEG_SUSPENDED;

      }

    }

    /* Completed an MCU row, but perhaps not an iMCU row */

    coef->MCU_ctr = 0;

  }

  /* Completed the iMCU row, advance counters for next one */

  if (++(cinfo->input_iMCU_row) < cinfo->total_iMCU_rows) {

    start_iMCU_row(cinfo);

    return JPEG_ROW_COMPLETED;

  }

  /* Completed the scan */

  (*cinfo->inputctl->finish_input_pass) (cinfo);

  return JPEG_SCAN_COMPLETED;

}

/*

 * Decompress and return some data in the multi-pass case.

 * Always attempts to emit one fully interleaved MCU row ("iMCU" row).

 * Return value is JPEG_ROW_COMPLETED, JPEG_SCAN_COMPLETED, or JPEG_SUSPENDED.

 *

 * NB: output_buf contains a plane for each component in image.

 */

METHODDEF(int)

decompress_data (j_decompress_ptr cinfo, JSAMPIMAGE output_buf)

{

  my_coef_ptr coef = (my_coef_ptr) cinfo->coef;

  JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;

  JDIMENSION block_num;

  int ci, block_row, block_rows;

  JBLOCKARRAY buffer;

  JBLOCKROW buffer_ptr;

  JSAMPARRAY output_ptr;

  JDIMENSION output_col;

  jpeg_component_info *compptr;

  inverse_DCT_method_ptr inverse_DCT;

  /* Force some input to be done if we are getting ahead of the input. */

  while (cinfo->input_scan_number < cinfo->output_scan_number ||

         (cinfo->input_scan_number == cinfo->output_scan_number &&

          cinfo->input_iMCU_row <= cinfo->output_iMCU_row)) {

    if ((*cinfo->inputctl->consume_input)(cinfo) == JPEG_SUSPENDED)

      return JPEG_SUSPENDED;

  }

  /* OK, output from the virtual arrays. */

  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;

       ci++, compptr++) {

    /* Don't bother to IDCT an uninteresting component. */

    if (! compptr->component_needed)

      continue;

    /* Align the virtual buffer for this component. */

    buffer = (*cinfo->mem->access_virt_barray)

      ((j_common_ptr) cinfo, coef->whole_image[ci],

       cinfo->output_iMCU_row * compptr->v_samp_factor,

       (JDIMENSION) compptr->v_samp_factor, FALSE);

    /* Count non-dummy DCT block rows in this iMCU row. */

    if (cinfo->output_iMCU_row < last_iMCU_row)

      block_rows = compptr->v_samp_factor;

    else {

      /* NB: can't use last_row_height here; it is input-side-dependent! */

      block_rows = (int) (compptr->height_in_blocks % compptr->v_samp_factor);

      if (block_rows == 0) block_rows = compptr->v_samp_factor;

    }

    inverse_DCT = cinfo->idct->inverse_DCT[ci];

    output_ptr = output_buf[ci];

    /* Loop over all DCT blocks to be processed. */

    for (block_row = 0; block_row < block_rows; block_row++) {

      buffer_ptr = buffer[block_row];

      output_col = 0;

      for (block_num = 0; block_num < compptr->width_in_blocks; block_num++) {

        (*inverse_DCT) (cinfo, compptr, (JCOEFPTR) buffer_ptr,

                        output_ptr, output_col);

        buffer_ptr++;

        output_col += compptr->DCT_scaled_size;

      }

      output_ptr += compptr->DCT_scaled_size;

    }

  }

  if (++(cinfo->output_iMCU_row) < cinfo->total_iMCU_rows)

    return JPEG_ROW_COMPLETED;

  return JPEG_SCAN_COMPLETED;

}

#endif /* D_MULTISCAN_FILES_SUPPORTED */

#ifdef BLOCK_SMOOTHING_SUPPORTED

/*

 * This code applies interblock smoothing as described by section K.8

 * of the JPEG standard: the first 5 AC coefficients are estimated from

 * the DC values of a DCT block and its 8 neighboring blocks.

 * We apply smoothing only for progressive JPEG decoding, and only if

 * the coefficients it can estimate are not yet known to full precision.

 */

/* Natural-order array positions of the first 5 zigzag-order coefficients */

#define Q01_POS  1

#define Q10_POS  8

#define Q20_POS  16

#define Q11_POS  9

#define Q02_POS  2

/*

 * Determine whether block smoothing is applicable and safe.

 * We also latch the current states of the coef_bits[] entries for the

 * AC coefficients; otherwise, if the input side of the decompressor

 * advances into a new scan, we might think the coefficients are known

 * more accurately than they really are.

 */

LOCAL(boolean)

smoothing_ok (j_decompress_ptr cinfo)

{

  my_coef_ptr coef = (my_coef_ptr) cinfo->coef;

  boolean smoothing_useful = FALSE;

  int ci, coefi;

  jpeg_component_info *compptr;

  JQUANT_TBL * qtable;

  int * coef_bits;

  int * coef_bits_latch;

  if (! cinfo->progressive_mode || cinfo->coef_bits == NULL)

    return FALSE;

  /* Allocate latch area if not already done */

  if (coef->coef_bits_latch == NULL)

    coef->coef_bits_latch = (int *)

      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,

                                  cinfo->num_components *

                                  (SAVED_COEFS * SIZEOF(int)));

  coef_bits_latch = coef->coef_bits_latch;

  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;

       ci++, compptr++) {

    /* All components' quantization values must already be latched. */

    if ((qtable = compptr->quant_table) == NULL)

      return FALSE;

    /* Verify DC & first 5 AC quantizers are nonzero to avoid zero-divide. */

    if (qtable->quantval[0] == 0 ||

        qtable->quantval[Q01_POS] == 0 ||

        qtable->quantval[Q10_POS] == 0 ||

        qtable->quantval[Q20_POS] == 0 ||

        qtable->quantval[Q11_POS] == 0 ||

        qtable->quantval[Q02_POS] == 0)

      return FALSE;

    /* DC values must be at least partly known for all components. */

    coef_bits = cinfo->coef_bits[ci];

    if (coef_bits[0] < 0)

      return FALSE;

    /* Block smoothing is helpful if some AC coefficients remain inaccurate. */

    for (coefi = 1; coefi <= 5; coefi++) {

      coef_bits_latch[coefi] = coef_bits[coefi];

      if (coef_bits[coefi] != 0)

        smoothing_useful = TRUE;

    }

    coef_bits_latch += SAVED_COEFS;

  }

  return smoothing_useful;

}

/*

 * Variant of decompress_data for use when doing block smoothing.

 */

METHODDEF(int)

decompress_smooth_data (j_decompress_ptr cinfo, JSAMPIMAGE output_buf)

{

  my_coef_ptr coef = (my_coef_ptr) cinfo->coef;

  JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;

  JDIMENSION block_num, last_block_column;

  int ci, block_row, block_rows, access_rows;

  JBLOCKARRAY buffer;

  JBLOCKROW buffer_ptr, prev_block_row, next_block_row;

  JSAMPARRAY output_ptr;

  JDIMENSION output_col;

  jpeg_component_info *compptr;

  inverse_DCT_method_ptr inverse_DCT;

  boolean first_row, last_row;

  JBLOCK workspace;

  int *coef_bits;

  JQUANT_TBL *quanttbl;

  INT32 Q00,Q01,Q02,Q10,Q11,Q20, num;

  int DC1,DC2,DC3,DC4,DC5,DC6,DC7,DC8,DC9;

  int Al, pred;

  /* Force some input to be done if we are getting ahead of the input. */

  while (cinfo->input_scan_number <= cinfo->output_scan_number &&

         ! cinfo->inputctl->eoi_reached) {

    if (cinfo->input_scan_number == cinfo->output_scan_number) {

      /* If input is working on current scan, we ordinarily want it to

       * have completed the current row.  But if input scan is DC,

       * we want it to keep one row ahead so that next block row's DC

       * values are up to date.

       */

      JDIMENSION delta = (cinfo->Ss == 0) ? 1 : 0;

      if (cinfo->input_iMCU_row > cinfo->output_iMCU_row+delta)

        break;

    }

    if ((*cinfo->inputctl->consume_input)(cinfo) == JPEG_SUSPENDED)

      return JPEG_SUSPENDED;

  }

  /* OK, output from the virtual arrays. */

  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;

       ci++, compptr++) {

    /* Don't bother to IDCT an uninteresting component. */

    if (! compptr->component_needed)

      continue;

    /* Count non-dummy DCT block rows in this iMCU row. */

    if (cinfo->output_iMCU_row < last_iMCU_row) {

      block_rows = compptr->v_samp_factor;

      access_rows = block_rows * 2; /* this and next iMCU row */

      last_row = FALSE;

    } else {

      /* NB: can't use last_row_height here; it is input-side-dependent! */

      block_rows = (int) (compptr->height_in_blocks % compptr->v_samp_factor);

      if (block_rows == 0) block_rows = compptr->v_samp_factor;

      access_rows = block_rows; /* this iMCU row only */

      last_row = TRUE;

    }

    /* Align the virtual buffer for this component. */

    if (cinfo->output_iMCU_row > 0) {

      access_rows += compptr->v_samp_factor; /* prior iMCU row too */

      buffer = (*cinfo->mem->access_virt_barray)

        ((j_common_ptr) cinfo, coef->whole_image[ci],

         (cinfo->output_iMCU_row - 1) * compptr->v_samp_factor,

         (JDIMENSION) access_rows, FALSE);

      buffer += compptr->v_samp_factor; /* point to current iMCU row */

      first_row = FALSE;

    } else {

      buffer = (*cinfo->mem->access_virt_barray)

        ((j_common_ptr) cinfo, coef->whole_image[ci],

         (JDIMENSION) 0, (JDIMENSION) access_rows, FALSE);

      first_row = TRUE;

    }

    /* Fetch component-dependent info */

    coef_bits = coef->coef_bits_latch + (ci * SAVED_COEFS);

    quanttbl = compptr->quant_table;

    Q00 = quanttbl->quantval[0];

    Q01 = quanttbl->quantval[Q01_POS];

    Q10 = quanttbl->quantval[Q10_POS];

    Q20 = quanttbl->quantval[Q20_POS];

    Q11 = quanttbl->quantval[Q11_POS];

    Q02 = quanttbl->quantval[Q02_POS];

    inverse_DCT = cinfo->idct->inverse_DCT[ci];

    output_ptr = output_buf[ci];

    /* Loop over all DCT blocks to be processed. */

    for (block_row = 0; block_row < block_rows; block_row++) {

      buffer_ptr = buffer[block_row];

      if (first_row && block_row == 0)

        prev_block_row = buffer_ptr;

      else

        prev_block_row = buffer[block_row-1];

      if (last_row && block_row == block_rows-1)

        next_block_row = buffer_ptr;

      else

        next_block_row = buffer[block_row+1];

      /* We fetch the surrounding DC values using a sliding-register approach.

       * Initialize all nine here so as to do the right thing on narrow pics.

       */

      DC1 = DC2 = DC3 = (int) prev_block_row[0][0];

      DC4 = DC5 = DC6 = (int) buffer_ptr[0][0];

      DC7 = DC8 = DC9 = (int) next_block_row[0][0];

      output_col = 0;

      last_block_column = compptr->width_in_blocks - 1;

      for (block_num = 0; block_num <= last_block_column; block_num++) {

        /* Fetch current DCT block into workspace so we can modify it. */

        jcopy_block_row(buffer_ptr, (JBLOCKROW) workspace, (JDIMENSION) 1);

        /* Update DC values */

        if (block_num < last_block_column) {

          DC3 = (int) prev_block_row[1][0];

          DC6 = (int) buffer_ptr[1][0];

          DC9 = (int) next_block_row[1][0];

        }

        /* Compute coefficient estimates per K.8.

         * An estimate is applied only if coefficient is still zero,

         * and is not known to be fully accurate.

         */

        /* AC01 */

        if ((Al=coef_bits[1]) != 0 && workspace[1] == 0) {

          num = 36 * Q00 * (DC4 - DC6);

          if (num >= 0) {

            pred = (int) (((Q01<<7) + num) / (Q01<<8));

            if (Al > 0 && pred >= (1<<Al))

              pred = (1<<Al)-1;

          } else {

            pred = (int) (((Q01<<7) - num) / (Q01<<8));

            if (Al > 0 && pred >= (1<<Al))

              pred = (1<<Al)-1;

            pred = -pred;

          }

          workspace[1] = (JCOEF) pred;

        }

        /* AC10 */

        if ((Al=coef_bits[2]) != 0 && workspace[8] == 0) {

          num = 36 * Q00 * (DC2 - DC8);

          if (num >= 0) {

            pred = (int) (((Q10<<7) + num) / (Q10<<8));

            if (Al > 0 && pred >= (1<<Al))

              pred = (1<<Al)-1;

          } else {

            pred = (int) (((Q10<<7) - num) / (Q10<<8));

            if (Al > 0 && pred >= (1<<Al))

              pred = (1<<Al)-1;

            pred = -pred;

          }

          workspace[8] = (JCOEF) pred;

        }

        /* AC20 */

        if ((Al=coef_bits[3]) != 0 && workspace[16] == 0) {

          num = 9 * Q00 * (DC2 + DC8 - 2*DC5);

          if (num >= 0) {

            pred = (int) (((Q20<<7) + num) / (Q20<<8));

            if (Al > 0 && pred >= (1<<Al))

              pred = (1<<Al)-1;

          } else {

            pred = (int) (((Q20<<7) - num) / (Q20<<8));

            if (Al > 0 && pred >= (1<<Al))

              pred = (1<<Al)-1;

            pred = -pred;

          }

          workspace[16] = (JCOEF) pred;

        }

        /* AC11 */

        if ((Al=coef_bits[4]) != 0 && workspace[9] == 0) {

          num = 5 * Q00 * (DC1 - DC3 - DC7 + DC9);

          if (num >= 0) {

            pred = (int) (((Q11<<7) + num) / (Q11<<8));

            if (Al > 0 && pred >= (1<<Al))

              pred = (1<<Al)-1;

          } else {

            pred = (int) (((Q11<<7) - num) / (Q11<<8));

            if (Al > 0 && pred >= (1<<Al))

              pred = (1<<Al)-1;

            pred = -pred;

          }

          workspace[9] = (JCOEF) pred;

        }

        /* AC02 */

        if ((Al=coef_bits[5]) != 0 && workspace[2] == 0) {