[SBE] The life of a spot after DG sends it to you...

[Ryan Salazar]

Thanks for all the comments. I just saw the spot on the air again here in Fort Lauderdale. Not sure how to describe the graphics, but there was a glowing white background around a logo. Right near where the glowing white starts, there's blue text and it's so "washed out". I just saw it on CBS. Not sure if it was a local or national buy, but I think it was national, so probably ran through more passes.

Ryan

-----Original Message-----
From: sbe-bounces at sbe.org [mailto:sbe-bounces at sbe.org] On Behalf Of Chris Spacone
Sent: Wednesday, May 20, 2009 8:41 PM
To: 'sbe member discussion mail list'
Subject: Re: [SBE] The life of a spot after DG sends it to you...

CBS may have pulled the spot from the SpotBox (it is just a Windows box) and
transcoded (perhaps using something like FlipFactory) it to the file format
used on by their video server. Poorly configured FF, low bitrates and a host
of other problems could account for the artifacts. Consider that the local
station that actually played the spot OTA may well have done something
similar to the spot.

As the source material undergoes multiple ingest / encodes / transcode
operations something called concatenation errors begin to creep in.
Essentially the quantization step reduces the 'dynamic range' (for lack of a
better way to describe it) of the video signal which can result in blocky
artifacts. These become more and more pronounced as the material undergoes
multiple passes. Quantization problems are clearly seen with the very low
bitrate video delivered by satellite services. If you watch a black field
you can see 'rings' or contours where the black jumps from one value to
another instead of being smoothly continuous. Another error introduced is
motion artifacting. As each frame of video is analyzed by the encoder a
series of decisions are made that determine how much of the picture can be
thrown away and how much should be kept. Motion vectors from frame to frame
are calculated and a series of MPEG I, P and B frames are generated as part
of a GOP (Group Of Pictures).

These artifacts can become quite obvious when the material has lots of very
small type / detail. If you can pause the playback and check  the edges of
vertical and horizontal elements you will see a sort of 'noise' (I have
heard it called mosquito noise). This noise is directly related to the
amount of quantization being applied to the video.

But all of this is speculation and partly lecture; unless you know the
precise chain the material took along each of the steps you are stuck
guessing. It is possible to 'objectively' measure the end result against the
source material and quantify the underlying impairments by using PQA
testing. Again, all this helps to do is objectively determine if there is a
problem, not precisely where it was introduced (or worse yet how to fix it).

Chris Spacone



-----Original Message-----
From: sbe-bounces at sbe.org [mailto:sbe-bounces at sbe.org] On Behalf Of Ryan
Salazar
Sent: Wednesday, May 20, 2009 12:12 PM
To: sbe member discussion mail list
Subject: [SBE] The life of a spot after DG sends it to you...

Everyone,

I figured this would be the best place for me to ask this question...

We send spots (post production facility), to DG Fast Channel via automation.
DG always tells us the spots look great, in fact, better than most spots
they receive. They then send the spot to stations via their "Spotbox".

Recently, we had an instance where they sent a spot to CBS-National. CBS
then fed the spot live via satellite to a local station. That local station
then fed it to the viewers. We received a complaint that the spot was
pixelated and blurry. I will admit, our disclaimers were way to small, but
we had strange artifacting that we don't normally have an issue with. I also
saw a considerable amount of blocks on the screen during fast movement of
graphics. I've seen this before after files were converted over and over.

I assume this is because of all the levels the file went through. Us to DG,
DG to CBS. Then, CBS via Satellite to the station and the station
broadcasts.

Any ideas? I know I can't really control all the points, but want to see
what else I can come up with.

Thanks!
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