/*
 * Copyright 2005 by the Massachusetts Institute of Technology.
 *
 * Permission to use, copy, modify, and distribute this
 * software and its documentation for any purpose and without
 * fee is hereby granted, provided that the above copyright
 * notice appear in all copies and that both that copyright
 * notice and this permission notice appear in supporting
 * documentation, and that the name of M.I.T. not be used in
 * advertising or publicity pertaining to distribution of the
 * software without specific, written prior permission.
 * M.I.T. makes no representations about the suitability of
 * this software for any purpose.  It is provided "as is"
 * without express or implied warranty.
 */

/**
 * @description
 * This file contains functions that allow one to decode MPEG-2 compliant video. 
 * The code is based on the MPEG-2 specification (ISO/IEC 13818-2). The MPEG-2 decoding
 * is a work in progress, although it works within a limited test range. Throughout the 
 * source code, citations are made in cases where an understanding of the code would be
 * helped by looking at an outside source. The format I have chosen is 
 * (cite NUM#, LOOKUP_INFO). NUM=1 refers to ISO/IEC: 13818-2, and NUM=2 refers to the reference
 * MPEG implementation written in C, available at [www.mpeg.org].
 *
 * @author <a href="mailto:madrake@gmail.com">Matthew Drake</a>
 * @file BlockDecode.str
 * @version 1.0
 */

/**
 * @internal
 */
int->int pipeline BlockDecode(portal<InverseQuantization_AC_Coeff> UpdatePortal_quantiser_data_ac,
                              portal<InverseQuantizationJoinerSubstitute> UpdatePortal_macroblock_intra,
                              portal<InverseQuantization_DC_Intra_Coeff> UpdatePortal_quantiser_data_dc) {
    add ZigZagUnordering;
    // Assumes no alternate_scan TODO
    // Output of this corresponds to QF[v][u], (cite 1, P. 67)
    add InverseQuantization_NoDefaultValues(UpdatePortal_quantiser_data_ac,
                                            UpdatePortal_quantiser_data_dc,
                                            UpdatePortal_macroblock_intra);
    // Extreme bounds for both saturations are a best guess about how far off
    // any invalid data could ever get.
    add BestSaturation(-2048, 2047, -2050, 2050);
    add MismatchControl();
    add iDCT8x8_ieee(2); // fast iDCT
    add BestSaturation(-256, 255, -260, 260);
}

/**
 * @internal
 */
int->int filter MismatchControl() {
    // (cite 1, P.71)
    work pop 64 push 64 {
        int sum, val;
        sum = 0;
        for (int i = 0; i < 63; i++) {
            val = pop();
            sum += val;
            push(val);
        }
        val = pop();
        sum += val;
        if ((sum & 0x1) == 0x1) {
            push(val);
        } else {
            if ((val * 0x1) == 0x1) {
                push(val-1);
            } else {
                push(val+1);
            }
        }
    }
}