[mythtv] ffmpeg SWSCALE!

Steven Adeff adeffs.mythtv at gmail.com
Thu Aug 31 01:16:34 UTC 2006


On 8/30/06, Michael T. Dean <mtdean at thirdcontact.com> wrote:
> On 08/30/06 19:12, Steven Adeff wrote:
> >On 8/30/06, Michael T. Dean <mtdean at thirdcontact.com> wrote:
> >>But, if done right, DVD's in 720x480 anamorphic widescreen on a 1080p TV
> >>can give nearly the same quality output as HDTV in 1080i/p on a 1080p TV...
> >>
> >>
> >rotfl! thats because all you've see is broadcast 1080i, which does not
> >come close to image quality that HD-DVD provides. HD-DVD, on a true
> >1080p display will blow. your. mind. Its truely a site to behold, even
> >PBS/InHD/HDNet can't come close to the bitrate and color palette that
> >HD-DVD will provide. HD-DVD also has the honor of holding uncompressed
> >surround sound. Where DVD's are AC3/DTS encodings (of usually
> >processed) theatre audio, HD-DVD will hold the uncompressed audio (and
> >from what I understand, unprocessed from what I hear as well.
> >
> >You just can't "make up" the information by upsampling.
> >
>
> True, but if you're processing the images correctly, you're not making
> up information (nor are you "upsampling"--i.e. 1 pixel becomes 4 or 9 or
> whatever).  Notice, however, the, "If done right," in my original statement.
>
> A digital image defines a set of samples, which can be displayed as is
> (i.e. a 1:1 pixel mapping) to /approximate/ the original image, or can
> be used with a proper reconstruction algorithm to recreate the original
> image /function/ from which the samples were taken (where the image
> function is a continuously-defined function, as opposed to the digital
> samples in the image itself).  If the image function is recreated, it's
> possible to resample the function for the desired number of pixels.  In
> doing so, no information is "made up"--instead, the information that's
> encoded into the original samples is just better applied.
>
> And, as mentioned in reply to your post in the thread, "Graphics card
> recomendation" (
> http://www.gossamer-threads.com/lists/mythtv/users/220344#220344 --mine
> will appear somewhere below there once the archive catches it), a
> display device needs at least 2x the pixels on each axis to fully
> represent the information in a given image.  So, a 720x480 DVD needs at
> least 1440x960 pixels.  And, a 720p TV has 1280x720 pixels, so you'd
> need a 1080p TV (with 1920x1280 pixels) to fully appreciate the images
> on the DVD.
>
> (BTW, the reply in the other thread is one which your laughter prompted
> me to actually send, after it sat in my Drafts folder for a day and a half.)
>
> In the real world, it's impossible to recreate the image function
> exactly from the samples that are taken--primarily because in the real
> world, signals are rarely band-limited.  Nonetheless, there is
> additional information in the image that can be extracted through an
> appropriate reconstruction process (and can result in a much better
> image given 4x the pixels for output).  Once you've reached a
> sufficiently-higher resolution than the image resolution (somewhere
> around 2x the pixels in each dimension), you will no longer see an
> improvement in picture quality.  At this resolution, you've used all the
> available information in the signal and eventually you will begin to
> bring out the artifacts/aliasing in the image.  But, as mentioned,
> 1920x1080 works quite well for DVD's...
>
> Besides, if you're talking about replacing DVD's with HD-DVD's,
> depending on the source, the studio may be "making up" as much
> information as the player that decodes the DVD.

I forgot about our previous thread, I'm going to research this myself
though, and see if I can't figure out what you say they say.

as for HD-DVD transfers, many of the early ones for broadcast *were*
DVD upscales, and it was painfully evident. Now though, because
studios are preparing for HD-DVD and have invested the money in the
proper transfer equipment, everything is being transfered at 4K
(maximum resolution of 35mm film) and then downscaled to 1080p for
HD-DVD.

-- 
Steve
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