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Digital cameras, printers and displays have their own established methods to measure their performance. Different
devices have their own special features and also different metrics and measuring methods. The real meaning of
measuring data is often not learnt until hands-on experience is available. The goal of this study was to describe a
preliminary method and metrics for measuring the objective image quality of the TV-out function of mobile handsets.
The TV-out application was image browsing.
Image quality is often measured in terms of color reproduction, noise and sharpness and these attributes were also
applied in this study. The color reproduction attribute was studied with color depth, hue reproduction and color accuracy
metrics. The noise attribute was studied with the SNR (signal to noise ratio) and chroma noise metrics. The sharpness
attribute was studied with the SFR (spatial frequency response) and contrast modulation metrics. The measuring data
was gathered by using a method which digitized the analog signal of the TV-out device with a frame grabber card.
Based on the results, the quantization accuracy, chroma error and spatial reproduction of the signal were the three
fundamental factors which most strongly affected the performance of the TV-out device. The quantization accuracy of
the device affects the number of tones that can be reproduced in the image. The quantization accuracy also strongly
affects the correctness of hue reproduction. According to the results, the color depth metric was a good indicator of
quantization accuracy. The composite signal of TV-out devices transmits both chroma and luminance information in a
single signal. A change in the luminance value can change the constant chroma value. Based on the results, the chroma
noise metric was a good indicator for measuring this phenomenon. There were differences between the spatial
reproductions of the devices studied. The contrast modulation was a clear metric for measuring these differences. The
signal sharpening of some TV-out devices hindered the interpretation of SFR data.
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