Re: ESPN HD

On Saturday, December 30, "Icon Smith" <icon@xxxxxxxxxxxxx> wrote:
>I believe what I am seeing is compression distortion, or mosquito noise.
>Today watching the Music City Bowl it seems just as bad on my LCD, but not
>on my plasma and DLP FP. Of course the LCD has a higher native resolution,
>so that is a contributing factor I'm sure. Could it really be the box? It is
>very similar to the image on the left in the attached photo link. Thanks.

> http://www.highdefforum.com/gallery/data/511/40Jpeg_distortion.jpg

To make sure I knew what Icon meant by "mosquito
noise", I did some Googling.  I was certainly familiar
with the type of artifact.  E.g., look around the
edges of characters on the display associated with any
of the music channels.

I found a review for a product which claims to correct
mosquito noise (for a mere $2500!):
http://tinyurl.com/y9dlqu 
For those who wish to understand the issue better, the
review provides a pretty good exposition of what is
going on.  The product also claims to be able to
correct the defect which I had been calling
"mosaicing" based on the following quote from the
Wikipedia article on MPEG-2 which I found about a year
ago:

    The output bit-rate of an MPEG-2 encoder can be
    constant or variable, with the maximum bit rate
    determined by the playback media ? for example the
    DVD movie maximum is 10.4 Mbit/s. To achieve a
    constant bit-rate the degree of quantization is
    iteratively altered to achieve the output bit-rate
    requirement. Increasing quantization leads to
    visible artifacts when the stream is decoded,
    generally in the form of "mosaicing", where the
    discontinuities at the edges of macroblocks become
    more visible as bit rate is reduced.

The above text can no longer be found in the
Wikipedia, so, though I welcomed the word, it is
apparently not in very common use.  The distinction
that I wish to make is between macroblocking which
occurs as a result of data transmission errors, in
which case the macroblocks are just flat wrong, and
macroblocking which occurs as a result of a picture
changing more rapidly than the encoder can keep up, in
which case the macroblocks are just poor
approximations with the result that you notice their
boundaries.  It is the latter sense of macroblocking
which the product claims to address, and they are
using the word "macroblocking" to describe such
artifacts.  These folks must certainly know what they
are talking about, so I am inclined to switch to
calling this type of macroblocking "compression-
induced macroblocking" (as opposed to "error-induced
macroblocking").

It had occurred to me also that, with sufficient
intelligence in one's decoder, it should be possible
to recognize the occurrence of compression-induced
macroblocking and to introduce some smoothing to
lessen its apparentness.  It had not occurred to me
that it might also be possible to recognize and filter
out mosquito noise.  The Algolith folks appear to have
succeeded in doing both.  I would expect such features
to start showing up in TVs because I don't think the
problems they address are going to go away.


Now, finally returning to Icon's issue:  No, I don't
think it could be the STB.  Although no problem with
the Cal/A&M game struck me, I have occasionally
noticed what appeared to be some sort of encoder
problem at ESPN which resulted in what I would call a
"shimmering" defect in certain saturated colors,
especially red, but independent of what camera it was
coming from.  When it has occurred, I regarded it as
an equipment problem - probably with the encoder.  I
have discovered that, when I find such artifacts to be
distracting, I can reduce the distraction by reducing
the sharpness setting on my TV.  (I will also go to
viewing the (smaller by a factor of 9/16) whole 16:9
picture instead of zooming the 4:3 middle up to the
full size of my 4:3 screen, as I often do with
football and basketball coverage (for which there is
never anything you need to see in the left and right
eighths of the pictures as they are currently being
formatted by the networks).  FWIW, in the Cal/A&M game
case I was watching the zoomed picture with a high
sharpness setting.)

Regards,
  David V.


The comments from me to which Icon was responding:
>> Indeed.  I regard their HD coverage for sports action
>> as the best.

>> I watched the game attentively; and, though I am quite
>> sensitive to picture defects, I thought it looked very
>> good.  OTOH, it is difficult to imagine a local
>> problem which could produce, for a digital feed, the
>> sorts of defects Icon describes.  I would almost be
>> inclined to attribute the problem to his STB; but I
>> suspect that Icon's LCD and plasma are using different
>> STBs, so a box problem is not a likely explanation
>> either.

>> Regards,
>>  David



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