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

[belcampo]

Jim Stichnoth wrote:
> 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
This is the maximum quality, within the right distance related to your 
screen-size, you will perceive.
The 1280*720p will scale to full-size 1366x768 and you don't have to 
deinterlace. Just my 2c
> 
> 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
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