[mythtv-users] Video Quality

Chris Delis cedelis at uillinois.edu
Thu Mar 11 14:35:26 EST 2004

On Thu, Mar 11, 2004 at 12:53:21PM -0600, Shay - MythTV wrote:
> At 11:04 AM 3/11/2004, you wrote:
> >And here I was hoping this was a discussion of the best recording or
> >transcoding settings...
> >
> >On Thu, 2004-03-11 at 11:25, Adrian Byng-Clarke wrote:
> >> How much of a video quality upgrade does one get by moving from a basic 
> >card
> >> like that to one of the PVR cards like the Hauppauge PVR 350. For example
> >> does the on board Mpeg 2 make that much of a difference? After all 
> >can't one
> >> just compress the signal after capture (sacrificing time and HD space for
> >> $$$) or is there more to it than that.
> >
> >The advantage of a card like my PVR-250 is that it encodes in hardware
> >so the CPU only has to deal with encoded video.  That's far less data.
> >With uncompressed video, your CPU is swamped with data.  If your CPU is
> >fast enough and your memory and bus bandwidth is high enough, you can
> >still get a perfect recording without hardware compression, but anything
> >that causes the CPU to get distracted will result in a glitch in the
> >recording.
> >
> >> Perhaps people could post samples of video captured. I don't want to get
> >> anyone in trouble - maybe they could just post something off of public TV
> >> etc... I just want to get a sense of the quality. For example Tivo's high
> >> quality setting looks to my eye exactly like the broadcast signal coming 
> >in
> >> - there are no artifacts on a TV.  Is this possible with a Linux PVR rig?
> >> Also is it only possible with the higher end capture cards?
> >
> >With a PVR-250, my first recording looked every bit as good as my
> >ReplayTV on high quality.  I intend to play with the recording profiles
> >a bit to see what I really want.  My guess is that I'll record at a
> >fairly high quality and then transcode things offline if we're keeping
> >them around for a while.
> >
> >But yes, Myth can provide results equivalent in quality to a TiVo with
> >hardware encoding (or with ATSC broadcasts, which are already encoded,
> >but that's another issue).
> Really?  I have yet to get my MythTV to record as well as my TiVo.  I have 
> a 250 and it just doesn't compare.  Its nice and all, but when things move 
> you see glitches.. artifacts.. I don't know the word for it.. its just not 
> smooth..

What are you viewing it on?  A monitor?  A TV?  If the former then that's because
it's interlaced video.  If the latter, then what sort of TVOUT are you using?
I have a 350 and I, for one, can not tell the difference between the original
broadcast and recorded programs (I've tested side-by-side Myth vs. DirecTV alone).
I don't see how TiVo can beat that.

> >> Personally I probably won't want to use mythtv to actually watch my
> >> recordings. I'm perfectly content saving them to DVD-R and watching them 
> >on
> >> my DVD player. I'm just wondering if that will look as good as the 
> >original
> >> broadcast or will it look strange. How successful is mythtv as a digital
> >> VCR?
> >
> >My Myth box is my DVD player.  But if you want to put Myth recordings on
> >a DVD, you'll need to record or convert them to MPEG-2.  You'll get the
> >best results if you use hardware encoding at DVD size and bit rates to
> >begin with (especially since Myth won't convert to MPEG-2, so you would
> >have to use an additional conversion program).
> >
> >--PC
> >
> >
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