I found this in my travels:
In reply to:
1. The per component versus system bandwidth issue
Insufficient bandwidth here starts to show up as loss of the finest picture details in analog video, and can lead to intermittent, partial, or total loss of the picture especially in digital video.
Bandwidth with no other qualification means the frequency range over which the frequency reproduced worst (or transmitted worst) comes out at least half as strong as the frequency that is reproduced best. The technical term for this is "not more than 3 decibels down".
If we have two components (each cable counts as a component) with a given bandwidth connected together, some frequencies may suffer the 50% loss twice which in terms of decibels is six dB down. Usually the greatest loss is at the top of the frequency range in question. So we might want to figure out where now is the highest frequency that still comes out at least half as strong as the best reproduced frequency. This is not an exact science and is not easy to measure. So experts simply pick a safety margin such as twice or three times the bandwidth. The more components in the video signal path, the greater the potential loss. For a typical home theater setup, there are two sets of cables and the audio visual receiver between the source device such as a DVD player, and the TV. I suggest choosing components with twice the bandwidth needed (up from a previous recommendation of 20% more bandwidth.). Some experts say you need three times the bandwidth for each component to almost guarantee a system frequency response no more than one dB down (less than 20% loss) at the highest video frequency desired.
For HDTV, which requires 37 Mhz system bandwidth, choose each piece of equipment to have at least 74 Mhz bandwidth if you are using component video connections.
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