[mythtv-users] am i dropping frames?

Steve Peters - Priority Electronics steve at priorityelectronics.com
Tue Jan 15 03:58:31 UTC 2008

-----Original Message-----
From: mythtv-users-bounces at mythtv.org
[mailto:mythtv-users-bounces at mythtv.org] On Behalf Of Brian Wood
Sent: Monday, January 14, 2008 7:52 PM
To: Discussion about mythtv
Subject: Re: [mythtv-users] am i dropping frames?

Steve Peters - Priority Electronics wrote:

>     Also, keep in mind, most recordings are just fine, but it's
>     noticable when i watch sports. Don't know why.

There are several reasons why sports programming tends to be more vulnerable
to digital artifacts:

It generally contains more "unpredictable" motion, requiring a lot more
processing power, and overflowing cheaper (ie: under $30,000) encoders.

Encoding has to be done in real time, pre-taped programming can be processed
at leisure, sometimes using multiple passes (it's not always, but it can

Sports programs are transported by fiber or satellite over twice as many
paths as a program that originates at the network studio (the "backhaul" is
added). Satellite and landline fiber both process heavily.

The program might be decoded and then re-encoded at your local affiliate (in
the case of an off-air station). CBS does this in order to be able to switch
commercials at baseband. Fox, OTOH, uses a device that allows then to insert
or switch into an MPEG stream, but both methods introduce artifacts.

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That all makes perfect sense, but when I plug my cable line directly into
the tv, the sports programs are great quality. Also, if I up the pvr-500 to
the max bitrate, I think that would be enough to offset this, but it
doesn't. Does anyone else have this issue, or do most of you have no problem
with sports?

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