[mythtv-users] Video Quality

Preston Crow pc-mythtv04 at crowcastle.net
Thu Mar 11 12:04:46 EST 2004

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

> 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).

> 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).


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