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Better than Best?
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Posted by: JeremyJ

I'm now a week into my personal Tivolution, and all I can say is, I can't believe I waited this long! I have already added a 120gHD for a total of 160GB (144 hour). More than my video editing computer!

My only complaint... Picture quality.

Even at "Best Quality", the picture is lacking in saturation and detail (especially chroma detail!), and suffers from motion artifacts. Based on the excellent quality of the boot up animation and the background graphics, I know the TIVO's MPEG decoder can do better, the question is can the MPEG encoder do better?

Strangely, if my math is correct, the current data-rate at "Best Quality" is actually about 1.2 MB/sec (that's Bytes not bits... bits are confusing to me) which is actually quite high. Higher than the highest possible on DVD. But few would agree that "Best Quality" is anywhere near DVD.

Obviously DVD-like 2-pass VBR isn't possible in realtime. And yes, I know, garbage in -> garbage out, however my analog cable picture is pristine, and Tivo really trashes it.

Is there a hack that can increase the data-rates of the various quality settings? Not that I'm convinced it would help, since I suspect the quality is being limited by the A/D converter and MPEG encoder chip. I personally would have happily paid $200-300 more for higher quality parts.

Nevertheless, I LOVE my Tivo. No other gadget has given me the lifestyle changing freedom that Tivo has. And whoever designed the interface should be awarded a medal or something. Making something as complex as Tivo THAT easy to use is nothing short of astounding.

Jeremy
I want Buffy in HDTV!

Posted by: stevel

The startup animation, like DVDs, are encoded by professional MPEG encoders that cost in the six-figures with trained technicians setting the parameters. That's beyond the capacity of the $50 (or less) chip on your TiVo.

What's your signal source? TiVo does best with a good, clean signal.

(Buffy in HDTV? I don't think my heart could stand that... :D )

Posted by: embeem

Check your preferences for "save disk space", it'll control rather the MPEG is CBR or VBR and will most likely have some effect on the quality.

Posted by: Tiger

I hate to say it but if you absolutely have to have the benefeit of top of the line video encoding, a standalone TiVo is not the way to go. I would disagree wih the statement that it would be impossible to get DVD quality in real-time. I assert that it is entirely possible, but cost prohibitive for a professional setup, let alone for a home box with a BOM sans hard drive of around/under $100

However, there are alternatives. Still TiVo, of course. But if you can stomache DBS, they use a much better encoder than TiVo ever could. If you get the DirecTV/TiVo combo box, there is no loss of picture quality due to re-encoding. When you play it back it will look as pristine (Or lack thereof, as sometimes their compression can have problems) as when it first aired. Their bitrate varies, a little below DVD quality is their max IIRC (For premium channels and sports) but since they can throw a lot more money at a single encoder for all their viewers, the picture looks much better than TiVo could with it's higher bitrate. And it takes much less space than the best setting.

Posted by: DJRobX

quote:
however my analog cable picture is pristine, and Tivo really trashes it.

I suspect it's not quite as pristine as you may think. It's probably full of RF "randomness" that appears very subtle to you when watched directly. You can usually see this noise much more clearly while you "FF" through something that TiVo's recorded.

Problem: RF distortion is random. MPEG compression works by eliminating redundancies. Randomness lacks redundancy. So, no matter what you do, your TiVo's compression is never going to look as good as, say, DirecTV's MPEG compressors, because you really DON'T have access to a noise-free pristine source like DirecTV does.

When DirecTV added locals, a lot of them were clearly being fed by off-the-air antennas. Even with their fancy-schmancy encoders, the results were often the same or worse than a standalone TiVo's recording at good quality! Having a true pristine source free of random garbage is everything when it comes to making high quality MPEGs.

Posted by: JeremyJ

Thanks for the tips guys. "Save disk space" was turned on. Hopefully turning it off will help a bit, I certainly have plenty of space.

Good point regarding noise, it's true RF noise tends to drive encoder's crazy. I guess if I had an extra $25,000 I could buy a Snell & Wilcox video noise remover. :)

Posted by: Worf

Heh, if you had $25,000 you'd buy yourself an MPEG encoder that's of way higher quality than the one in the TiVo and avoid all the problems :).

Posted by: ADent

There was some talk ahile ago of adjusting the quality, but I think it was an old 2.0 thread or earlier.

A DirecTiVo looks a lot better, but you have to deal with DTVs somewhat overcompressed signal.

Posted by: hfwarner3

quote:
Originally posted by JeremyJ
I want Buffy in HDTV!

Don't we all, my friend ... don't we all. :D

Posted by: Tiger

DirecTVs signal has gotten better this year, when they were able to offload most of the LILs off the CONUS transmission. Either way, even their overcompressed signal looks better than a TiVo with a pristine signal, and most people can't get a pristine signal.