6Mb/s is not necessarily required. You just have to allocate enough to satisfy the resolution and compression factor (determined by content).
Also, analyze an MPEG in software called "BITRATE VIEWER" and watch the true curve and peaks. What you see in other software or DVD players may not be accurate.
About bitrate allocation, read this:
http://www.digitalfaq.com/dvdguides/...tm#mpegbitrate
You have "used" sources. They have been encoded/transferred probably 2-3 times now before you get them on tv. Studios have perfect film or digital. Yours will never look 100% as good, but it's still close enough to not be overly critical about it. You also have far inferior video equipment compared to them.
Simply stated, pros don't capture. They don't need to. They scan film or use digital sources they shot from.
I use 352x480 with a 2.0-4.5 VBR hardware compression on a lot of my stuff, and I have good hardware, so I can achieve outstanding results. And that's about as good as it'll get for any of us. Even if I upped it to 10+ MB/s, it won't do anything, overkill and unused, serves only to bloat discs.