\chapter{Introduction}

This master's thesis describes the design process of a measurement instrument for video playback measurements.
The design work done by the author and described in this thesis includes the choice of hardware components, design of the electronic circuit and circuit board, design of custom enclosure, choice of software platform and implementation of the software running on the device.
The purpose of the instrument, shown in Figure \ref{fig_device}, is to aid in the development of video playback devices, such as tablets, smartphones and televisions.

\begin{figure}[h]
\centering
\includegraphics[width=14cm]{pictures/device.jpg}
\caption{The device designed in this thesis work.}
\label{fig_device}
\end{figure}

The number of different models of video playback devices in development is nowadays higher than ever previously and new models are introduced every year.
Popular examples include Apple's iPhone smartphones and iPad tablets, and the Android-based smartphones and tablets available from multiple manufacturers.
An important part of the user experience on these platforms is the smooth playback of videos, game graphics and user interface animations.
However, verifying the playback quality is a challenge.

If the video playback quality cannot be measured, it is likely that defects and inefficiencies will remain in the devices. These will eventually show up to the users, possibly only occasionally such as jitter that is visible in only certain kinds of motion. The user does not even need to consciously notice the problem for it to affect the \emph{feel} of smoothness.

Most common methods are to add instrumentation to the programs, or to have a human perform subjective evaluation. See \cite{uxtune} and \cite{itu_opavc}, respectively, for examples of these methods.
Instrumenting the programs is often straight-forward, but doesn't allow comparisons to competitor products,
verifying the product in the exact same configuration as the customer would use nor does it detect problems that occur in the display hardware.
Subjective evaluation is expensive and does not provide exact, repeatable results, which makes it difficult to use during the development process.

\begin{figure}[h]
\centering
\includegraphics[width=14cm]{pictures/meassetup.jpg}
\caption{An example measurement setup where the video playback performance of a laptop computer is being measured.}
\label{fig_meassetup1}
\end{figure}

OptoFidelity Oy \cite{optofidelity} is a company specialized in an external measurement method: the image on the screen is monitored using a high-speed camera or other sensors.
This allows the verification of the complete playback path, including the display hardware.
One of the product lines based on this principle is the \emph{Frame Rate Meter}\cite{frm120}, which uses a graphical marker embedded in the video stream in order to measure frame times.

The device described in this thesis, called \emph{Video Multimeter}\cite{videomultimeter}, is a continuation of this product line. It improves upon the previous version by adding more capable sensors and by allowing more extensibility for various measurement purposes, while retaining the basic mode of operation. Figure \ref{fig_meassetup1} shows an example of the measurement setup, where the marker is located at the upper right corner of the video and is measured using a fiber-optic sensor.

The rest of the thesis is divided into four parts. The first chapter will provide general background on video playback performance measurement, and describe in detail the challenges involved. The next two chapters will explain in detail the development of the measurement device, done as part of this thesis work. The final chapter will analyze the results of the work based on the achievement of goals and the customer feedback received for the pilot version.
