/*
 * 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 ChannelUpsampling.str
 * @version 1.0
 */

// Note: We assume we are going from 4:2:0 to 4:4:4
// Otherwise this won't work.
// Check out store.c in the mpeg reference implementation
// It has a more complicated, probably more accurate
// implementation. Only implement if needed.
/**
 * @internal
 */
int->int pipeline ChannelUpsample_Vert_and_Horz(int sourcewidth, int sourceheight) {
    add ChannelUpsample_Vertical(sourcewidth, sourceheight);
    add ChannelUpsample_Horizontal(sourcewidth, sourceheight);
}

int->int splitjoin ChannelUpsample_Vertical(int sourcewidth, int sourceheight) {
    split roundrobin(1);
    for (int i = 0; i < sourcewidth; i++) {
        add ChannelUpsample_1D(sourceheight, 3, 1, 2);
    }
    join roundrobin(1);
}

int->int splitjoin ChannelUpsample_Horizontal(int sourcewidth, int sourceheight) {
    split roundrobin(sourcewidth);
    for (int i = 0; i < sourceheight; i++) {
        add ChannelUpsample_1D(sourcewidth, 1, 1, 1);
    }
    join roundrobin(sourcewidth*2);
}

/**
 * @internal
 * 
 */
int->int filter ChannelUpsample_1D(int sourcelen, 
                                   int weight1, 
                                   int weight2,
                                   int shiftAtEnd) {
    work pop sourcelen push sourcelen*2 {
        int val1 = 0, val2 = 0;
        // keep track of product of weights to avoid extra multiplies
        int w1val1, w1val2; // weight1 * val1, weight1 * val2
        int w2val1, w2val2; // weight2 * val1, weight2 * val2

        val1 = pop();
        w1val1 = weight1*val1;
        w2val1 = weight2*val1;

        push(val1 >> shiftAtEnd);
        for (int i = 0; i < sourcelen-1; i++) {
            val2 = pop();
            w1val2 = weight1*val2;
            w2val2 = weight2*val2;

            int outval = (w1val1+w2val2);
            push(outval >> shiftAtEnd);
            outval = (w2val1+w1val2);
            push(outval >> shiftAtEnd);

            w1val1 = w1val2;
            w2val1 = w2val2;
        }
        push(val2 >> shiftAtEnd);
    }    
}