DCT domain filter for ATV down conversion

There has been a lot of interest in ATV down-conversion for cheaper implementation of ATV. Instead of expensive high definition monitors, down conversion allows using inexpensive existing monitors such as NTSC or 525 progressive monitors by converting a high definition input picture into a lower resolution picture. Low pass filtering is necessary prior to downsampling. Truncation of high DCT coefficients is a commonly used practice. The proposed DCT filter is a suboptimal filter which is equivalent to a block mirror filter in the spatial domain, but with less hardware.