[mythtv-users] Capture sharpness

Rod Smith mythtv at rodsbooks.com
Sun Nov 25 19:08:42 UTC 2007

On Sunday 25 November 2007 13:41:17 Jay Mallar wrote:
> I'm using a PVR-250 to capture TV via my DirecTV STB.  On my TiVo, I get
> much better capture quality in terms of picture sharpness than I do with
> the PVR-250.
> I can't seem to find anything that will allow me to control the
> sharpness of the capture, is there a way to modify this?  or is this
> just an indication that PVR-250's aren't as good as the Tivo captures?

There could be any of several factors at work here; you've not provided 
information on this critical information:

- Is your TiVo a standalone (SA) unit or a DirecTiVo? If the latter, it will
  produce better quality because it records the digital bitstream directly,
  whereas MythTV records the decoded analog output from a set-top box, which
  imposes an extra digital->analog->digital conversion cycle.

- What inputs are you using? S-video is better, composite is middle, and
  coaxial (RF) is worst. If you're using S-video for your TiVo and RF for
  MythTV, that could explain it.

- What are your quality settings? (Resolution and bitrate, mainly?) These
  impact quality. SA TiVos also have quality settings, although they're
  expressed as Best, High, Medium, and Basic, IIRC, and I don't know the
  precise mapping of those to resolutions and bitrates.

- What type of DirecTV receiver(s) do you have? I've seen claims that they
  vary in video output quality, so it's conceivable that you've got one with
  better quality feeding your TiVo and one with worse quality feeding your
  MythTV box.

- Have you checked your cables? Loose or low-quality cables can cause
  problems. (That said, the high-priced premium cables sold by many retailers
  are overpriced scams, IMHO. Just be sure you're not using something very
  old, frayed, or designed for the wrong purpose.)

These issues aside, I've never done a direct comparison of a TiVo to a 
PVR-250, so I can't promise that the latter can equal the former in image 
quality. I'd be surprised if the differences were huge, though.

Rod Smith

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