#!/usr/bin/bc
#
# videocalc.bc - Copyright (c) 2003 Nikolaus Rath <Nikolaus@rath.org>
# 
# Distribution and use allowed under the terms of the perl license.
#
scale=10

# CONFIGURE THIS:
# The preferred resolution, achieved with quality=1
res_max = 640 * 480
# The preferred bpp, achieved with quality=1
bpp_max = 0.26
# The minimum resolution
res_min = 528 * 240
# The minimum bpp
bpp_min = 0.18
# END CONFIGURABLE SECTION

# Input
print "Enter actual width in pixels: "
width_old = read()
print "Enter actual height in pixels: "
height_old = read()
print "Enter desired quality (0 - 1) or bitrate (>1): "
input = read()

# Max shouldn't exceed actual size, we don't want
# to make the video bigger
if(res_max > width_old * height_old)
    res_max = width_old * height_old

# Min shouldn't exceed actual size
if(res_min > width_old * height_old)
    res_min = width_old * height_old

if(input > 1) {
    # Bitrate
    bitrate_des = input

    # Calcute quality for desired bitrate
    rb_max = res_max * bpp_max
    rb_des = (bitrate_des * 1000) / 25
    quality = rb_des / rb_max 
} else {
    # Quality was entered directly
    quality = input
}

# Calculate BPP and resolution for quality
bpp_des = bpp_min + (bpp_max - bpp_min) * quality
res_des = res_min + (res_max - res_min) * quality

# Calculate final width and height based on resolution
# (using aspect ratio and ensuring that width and height
# are multiples of 16)
rscale = sqrt((res_des) / (width_old*height_old))
if(rscale >= 1) {
    # Old resolution is lower than new resolution, we
    # increase max. 10 pixels or decrease max. 6 pixels
    # to ensure beeing n*16
    width_new = width_old + 10
    height_new = height_old + 10
} else {
    width_new = rscale * width_old
    height_new = rscale * height_old
}
scale=0
width_new -= width_new % 16
height_new -= height_new % 16

# Calculate effective reached bitrate
bitrate = (25 * width_new * height_new * bpp_des)/1000

print "Quality: ", quality, "\n"
print "BPP: ", bpp_des, "\n"
print "Size: ", width_new/1, "x", height_new/1, "\n"
print "Bitrate: ", bitrate, "\n"

quit