A Performance Analysis System for the Sport of Bowling

possible to roll up to 21 shots in one game of bowling. Allowing a maximum of 512
bytes per ball (500 samples, plus some additional header information), 10752 bytes are
required to store the "worst-case" game: 21 balls thrown at 10 mph.
Serial EEPROM is now available in 8Kx8 (64K bits), 16Kx8 (128Kk bits), and 32Kx8
(256K bits) chips, with 64Kx8 (512K bits) soon to be available. The 16Kx8 chip is
mandated using the above criteria. If a sample rate of 240 Hz is required, the 256Kb
module would have to be specified, with a commensurate increase in cost. At a 120Hz
data rate, the 256Kb chip will also accommodate three full games of bowling, which is
significant, since a league series usually consists of three games.
The above calculations are based on minimum ball speeds (maximum sample time per
ball). However, a greater number of shots can be captured for a given size memory if the
data is stored in variable length records. Such a record would consist of header
information (the ball count, the activation count, the run time, the length of the record, a
pointer to the previous record, a pointer to the next record, etc.) and the actual sample
data. The records would be stored as a doubly-linked list, and uploaded as a group,
probably at the end of each game, which would free up the memory for the next game.
2.9.4 Data Compression
Although serial EEPROM memory has increased in capacity while also becoming
cheaper, it is cost-effective to use the smallest memory space that will hold a game's
worth of data (21 balls maximum). The data collected so far might possess
characteristics that could be exploited by a data compression routine. Bearing in mind
that the collected waveforms are from a single bowler and a single bowling
establishment, it would be incorrect to assume that this data is representative of the entire
bowling population. However, it should be possible to draw some initial useful
conclusions that are worth further study.
It was originally assumed that the waveform the SMARTDOT module records would have
a roughly sinusoidal shape. Looking at just the lower half of the waveform, that
assumption is basically valid. However, the waveform exhibits striking directionality
when the module is facing the ceiling, as can be seen in Figure 2-10. By setting 0° to be
that point where the module is facing directly toward the ceiling, it is apparent that the
sample-to-sample values change rather rapidly (20 or more counts at a time) in the range
from 270° to 90°. This phenomenon results from the fluorescent ceiling lights acting as
point sources, rather than as a uniformly distributed light source, and from the module
being located below the surface of the ball.
However, the sample-to-sample values in the 180° of rotation between 90° and 270°
change relatively slowly (only a few counts at a time). This portion includes the valleys
of the waveform, which are produced when the module faces the lane surface, in the
shadow of the ball. The "interesting" portion of the waveform falls within the range 10-
50 (0x0A to 0x32), where the waveform exhibits a finer granularity. This information
can be used to advantage in contemplating appropriate data compression techniques.
A system needs to be established that can store two samples in one byte - 4 bits per
sample. If samples could be stored as a value relative to each other, or relative to some
known fixed value, this goal might be accomplished. It would be beneficial to maintain a
fine granularity around the inflection points of the valleys in the waveform, and loosen
that granularity as the sample values move further away from those inflection points.
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