[mythtv-users] DISH+HD-PVR - best resolution?

[Jim Stichnoth]

On Thu, Sep 10, 2009 at 6:24 PM, drew einhorn <drew.einhorn at gmail.com> wrote:
> On Thu, Sep 10, 2009 at 6:07 PM, Jim Stichnoth <stichnot at gmail.com> wrote:
>> My DISH Network receiver is a ViP 211.  Its output can be set to 1080i
>> or 720p (or 480i as well, I suppose).  I am using an HD-PVR for
>> recording programs from DISH.  I am using VDPAU to display at my TV's
>> native resolution of 1366x768.
>>
>> Does anyone have opinions on whether I should set the ViP 211 to 1080i
>> or 720p?  Will there be differences in picture quality, MythTV/HD-PVR
>> stability, or file sizes?  For what it's worth, the web seems to
>> indicate that DISH's HD content is sent in a weird 1440x1080i format.
>> So no matter what, the ViP 211 will do its own scaling (and possibly
>> deinterlacing), and then VDPAU will rescale (and possibly deinterlace)
>> for my TV.
>>i
>
> There is no one best size.  It will vary depending on the content.
>
> Some content is produced at low res, and somewhere along the way
> It may be upscaled/upconverted to a higher resolution, which may
> help to reduce some artifacts when viewed on a high res display, but
> it can not add new detail to the images.  The video can be downscaled
> back to the original res with little or no degradation in image quality.
>
> Higher res uses more disk space.
>
> I can imagine a tool the analyzes video and determines the
> optimal resolution for storage, balancing file size and image
> quality.  But I am not aware that such a tool exists.
>
> If someone knows of such a tool, please tell us about it.

I probably wasn't clear enough about my question, so I'll expand on it.

DISH sends their HD content to my receiver in some format (such as
720p or 1080i).  I assume they always use the same format for HD
content, regardless of its source, but I could be wrong.  I have read
that this format is actually not 720p or 1080i, but rather 1440x1080
interlaced.  Again, this could be incorrect.  I wonder if anyone has
definitive information on this.  Regardless of the format delivered
over the satellite, my receiver has to be fixed to always output at
either 1080i or 720p, so the HD-PVR is always recording that
particular format.  Both formats are different from my TV's native
resolution of 1366x768.

So there are several format changes going on.  Depending on how I set
the receiver output, it could be:
  1440x1080i --> 1920x1080i --> 1366x768p
or
  1440x1080i --> 1280x720p --> 1366x768p

Each format change introduces some degradation of quality.  I'm mostly
wondering how to minimize the total degradation.  Now that I actually
write it down, it seems that the first option (setting the receiver to
1080i) should be better, since the first conversion will scale just
horizontally and not vertically.  I assume that my ION can deinterlace
as well as the DISH receiver, so maybe I ought to be using the 1080i
output on the receiver.  I vaguely recall early recommendations to
avoid 1080i on the HD-PVR because of stability problems, but now I see
that the latest firmware should be OK even with switching formats
mid-program.

Jim