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Discussion Starter · #1 ·
I've got extractRTV working great but when I play the extracted mpgs on my pc, there's some weird green garbage along the top edge of the image... any ideas?



tnx.:rolleyes:
 

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I just did some extracting of both low and high quality streams.


The "garbage" you see along the top edge is the "digital" information that is sent in the top scan lines of the video signal. This is where they put all that extra stuff like closed captioning.

On a TV these codes are just off the top of the screen in an area they called the overscan area.


since these scan lines are included in the encoded video signal they cause artifacting along the top of the actual tv picture.

You can even see this when you are watching the replay along the top, but it's not too noticable.


I'm not sure what the green line is on the side. It may be a horizontal "overscan"


Justben is not correct about these problems not appearing in the medium and high quality. It happens in all of them.
 

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The "weird green garbage" that SeTeS is seeing is in fact an encoding artifact unique to the lowest quality setting on sutter-class hardware. It typically manifests itself as green pixels across the top two lines of active video.


Closed-captioning information, CGMS-A, EDS, and other data transmitted in the vertical blanking interval (VBI) is not encoded in the MPEG2 stream (which is why closed-captions on pre-3000 series units is not available).


Perhaps a more detailed analysis of the extracted streams should be performed, hastypete? ;)


Ben.
 

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Discussion Starter · #5 ·
Hmm.... well, I just upped my 30hr SS to 80hr and was -about- to switch to medium level recordings, but it looks as if that won't do any good.



So, is this something that can be remedied by reencoding or are the artifacts -there-?
 

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:confused:

I could be wrong.

I'm basing my response on my experience with extraction.

You can plainly see the closed captioning and other digital data at the top of every show I've extracted so far at every level of compression.

The only green stuff I'm seeing is a vertical line at the right side. It is not pixelation, but a very stable bar.


I do know what the closed captioning looks like, I've worked with a few old TVs that had the vertical a little too low and showed it.


I also know that the video I extracted is of highest quality. 1.5Gig for 30 minutes.


I'd upload some pics, but I'm too lazy right now to figure out how to get a screen capture (printscreen?, does that work with MPEG player?)


Here's a thought, maybe different codecs show the picture differenly. Don't know, the only thing I've installed that would be playing these streams is WinDVD.


- hastypete
 

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So I did some research into this and found out what is probably going on...


It seems that some broadcasters are transmitting data in the first few lines of active video (which starts on line 22). It looks like the active video region is being shifted up by about four lines on the replaytv video outputs, effectively hiding the "garbage" behind the vbi.


You can check out the "garbage" in the source video signal (it seems to show up quite a bit on my cable CNN feed -- ymmv) by using an underscanning monitor or an old tv or video monitor with a vertical hold knob.... just tweak the knob until you can see the vbi region on the screen.


Ben.
 

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Sorry if this has been answered before, I did a search but it came up nothing, and this thread seems to be the closest match to it.


Is there any MPEG2 viewer that has a setting to let you watch the "Active Viewing Area" only? So we don't see the signal in the overscan area? If not, which software can do post processing to crop that? Does Premier 5 or 6 support MPEG2?


I am also thinking about transcoding the files to WMV format so I can store them, but I need to reencode them down to MPEG 1 first. Any software that can do this? Perhaps the easiest way to do this is to uncompress it to a raw AVI file?


Thanks fo rthe help!
 

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Quote:
Originally posted by upa123
Is there any MPEG2 viewer that has a setting to let you watch the "Active Viewing Area" only? So we don't see the signal in the overscan area? If not, which software can do post processing to crop that?
What I did for this was just size a frame and slide it off the screen a few pixels. I have so many players installed I can't remember which one worked best. But that is a great question anyone know of a software player that allows over/underscanning settings like DScaler?


Another approach is playing these on a Sampo DVD player and it was reported that the normal TV overscan was suffecient for this but I haven't had the chance to try it yet.
 

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line 24 I believe (it's been a long time since I needed to know that) is teh first line to be shown on any tv without overscan. That falls outside the "safe" zone.


If you play back this stream on a tv from DVD or SVCD you won't see that extra garbage. Your tv might just show you the close caption data that is encoded in that "garbage".


There is lots of other stuff in those first few lines.


The use of VBI here is a bit misleading. VBI is the interval that start when the gun reaches the bottom right of the screen the VBI is the time it takes the gun to get to the top of the upper left of the screen. VBI generally starts at line 224. This is outside the "safe" viewable region. The VBI stops at line 0, and no data is transmitted during the real VBI that I know of. From 0-18 are used for sync and data starts coming in around line 20 or so. Many things do get sent in this "unviewed space", three or four different CC signal, time info, channel info, program info, enhanced tv data, any of this stuff is being gatered at a rate of something like 8 bytes every 60th of a second, or 480 bytes a second.


The safe zone on every tv is different, no tv's can reliably show the exact content. That is just the way NTSC is, DTV is different, but still with a VBI.


If you use the overscan monitor hooked up to any source you should be able to get that same "garbage".
 
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