[mythtv-users] PVR 350, closed captioning, commercial detection

mail2 Pascal.Favre at gmx.net
Mon Aug 8 17:00:30 UTC 2005

Hello Chris

Great explanation. About point 4. Does it only look for the watermark in the lower right corner ?
Looking at German/Swiss/Austria Television it would only catch one channel (RTL-2).
80% use the upper right  corner, the others use the upper left corner.
You think mythcommflag has to be changed to do a better job ?


----- Original Message ----- 
From: <chris at cpr.homelinux.net>
To: "Discussion about mythtv" <mythtv-users at mythtv.org>
Sent: Monday, August 08, 2005 6:06 PM
Subject: Re: [mythtv-users] PVR 350, closed captioning, commercial detection

> On Mon, Aug 08, 2005 at 08:57:28AM -0400, Scot L. Harris wrote:
>> On Mon, 2005-08-08 at 01:05, Jesse D. Guardiani wrote:
>> > Also, what about commercial detection? Is that supposed to work with
>> > PVR-x50's, or not? If it is, then I'd love to figure out what I need
>> > to change to make it work on my system.
>> Commercial detection works just fine with my box which has a PVR-350 and
>> a PVR-250 in it. 
> Commercial detection is not dependent on the type of input device.  The
> success rate varies depending on the station, though, as many are now
> taking active steps to foil commercial detection.
> There are (or were, anyway) at least five ways to detect commercials:
> (1) Networks used to insert a countdown signal in the pre-scan region at
> the top-right of the screen.  It was a little white box that would
> blink and then go solid just before the commercial.  The regional
> stations would use that as a guide for inserting local-run commercials.
> I don't think that system is used any more.
> (2) Some shows used to carry the time signal above frame where CC is now
> located, so you could watch for a break in the time signal.  I don't
> know if it's still there or not.
> (3) There is usually a few frames of black and silence between shows and
> commercials and between commercials.  It's easily detected.
> (4) Many stations use a "watermark" in the lower right corner of the
> screen so you'll always know what station you're watching (or where the
> recording came from).  That dissappears during commercials.
> (5) Commercial sound levels are usually a few dB louder than the show
> they are breaking.  Stations don't care if you fall asleep during the
> movie as long as the first thing you see when you wake up is a beer
> commercial. :-)
> AFAIK, MythTV detects using #3 and #4.  Some stations are running the
> commercials closer together to eliminate the breaks, or at least time
> the first one to cut into the show.  My MythTV usually misses the first
> commercial because there's no blanking, but catches the second one.
> MyTH's commercial detection tends to break down during the last break
> before the end of the show.  Many stations will run 3 or 4 minutes of
> commercials and then come back for the closing statement (or
> cliffhanger) and then roll credits.  Myth can see the breaks but can't
> tell which are commercials and which are the show because the final show
> segment is too short.


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