Sampling-Rate Conversion of Video Signals

Ajay Luthra, Ganesh Rajan

Encoding analog component video to a composite signal is an established practice. Improvements are constantly being made in encoding techniques, with the result that the quality of the encoded video is closer to that of the component source. Encoding digital components to digital composite signals involves an additional step besides coding: the sampling-rate conversion. The sampling rates of component video signals (CCIR Rec. 601) are 13.5 Msamples/sec and 6.75 Msamples/sec, for the luminance and the color-difference signals, respectively. The sampling rates for NTSC and PAL composite video signals are 14.3181818 Msamples/sec and 17.734475 Msamples/sec, respectively. Clearly, decoding digital composite signals into digital component signals (CCIR 601) will also involve the sampling-rate conversion. This task of sampling-rate conversion further complicates the issues related to the quality of the output video. It introduces a new class of distortions, called linear time varying distortions, in the output signal. This article explores the techniques necessary to convert between digital signals with different sampling rates and presents a qualitative comparison of the two approaches, analog and digital, to the sampling-rate conversion.

Print ISSN
Published
1991-11
Content type
Original Research
DOI
10.5594/J02406