Date: Sun, 24 Feb 2008 17:03:47 +0000 From: Dieter <freebsd@sopwith.solgatos.com> To: freebsd-multimedia@freebsd.org Subject: Re: Kbtv2 beta2 uploaded Message-ID: <200802250103.BAA25580@sopwith.solgatos.com> In-Reply-To: Your message of "Mon, 25 Feb 2008 00:56:18 %2B0100." <200802250056.18550.danny@ricin.com>
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In message <200802250056.18550.danny@ricin.com>, "Danny Pansters" writes: > On Friday 22 February 2008 18:59:44 Dieter wrote: > > > > > Your card seems to have a microtune tuner mt2050 which is not yet > > > > > supported by the saa backend. I'm looking into it. Unfortunately it > > > > > differs from the other generic tuner APIs for saa in that tuning and > > > > > init are to be handled differently (mt2032 is supported by bktr, so I > > > > > can peek there). THis is an important tuner to have support for > > > > > though for several reasons: > > > > > > > > > > - it's on a chip, not in a large chunky metal enclosure > > > > > > > > I have read that the very small USB tuners don't perform as well as the > > > > "large chunky metal enclosure", because some features were left out. > > > > > > Well, they don't have an mpeg encoder chip, but neither do the old > > > fashioned analog TV cards. Of course, supporting that A/V decoder is > > > another matter. But so is supporting an onboard mpeg encoder. > > > > > > They seem to use empia chipsets almost exclusively, the variant without > > > onboard MPEG encoder is called the "blackbird" design IIRC. > > > > No, I mean the reception performance, not mpeg features. The "big" metal > > cans supposedly have better RF filtering. Keeping the undesired > > frequencies out is important. > > I've been looking into how they work and what they do is they have two IF > stages. They demodulate to higher frequencies first (order 1200 MHZ) then do > the usual demod to actual IF (for PAL, ntsc, but also QAM etc). I think you mean "frequency shift" aka "mix" rather than "demodulate"? http://en.wikipedia.org/wiki/Modulation http://en.wikipedia.org/wiki/Frequency_mixer http://en.wikipedia.org/wiki/Heterodyne http://en.wikipedia.org/wiki/Superhet
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