clear QAM on ATI DTV Wonder capture card - purple lines - AVS Forum
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post #1 of 26 Old 03-29-2012, 12:09 PM - Thread Starter
 
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Hello. I was wondering if anyone has seen or has any suggestions for my issue:
I have MythTV with an ATI DTV Wonder capture card. I ran the channel scan and it found all of the expected channels, however the channels have many verticle purple digital looking lines, making the picture unwatchable. I tried to run dvb-apps scan tool, but it output a TON of stuff. What should i do next?

Note: I also have a dual analog tuner card that works ok, however there is alot of fuzz in the picture. (maybe its just the card in the PC?) the signal looks better when plugged directly into the tvs analog tuner.

P.S. this is for comcast cable, so it has both analog and digital channels on it.
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post #2 of 26 Old 03-29-2012, 01:38 PM
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Hello. I was wondering if anyone has seen or has any suggestions for my issue:

Can't say that I have seen this such an issue, but I do have the following suggestions, statements and questions that might help you progress towards resolving the issue.

Quote:


I have MythTV with an ATI DTV Wonder capture card. I ran the channel scan and it found all of the expected channels, however the channels have many verticle purple digital looking lines, making the picture unwatchable.

Just to be clear (because you also discuss analog later on), the channel scan you did was for digital channels on cable and the reception problem with the purple lines you're referencing is strictly related to the digital channels, and not problems in the analog channel reception?

Remove MythTV from the equation, and drop back to stand alone apps for testing (see next suggestion).

Quote:


I tried to run dvb-apps scan tool, but it output a TON of stuff. What should i do next?

the scan tool will output both encrypted and unencrypted digital channel/services it finds and you'd have to go through them one by one (writing the output to a channels.config and then using something like xine, Mplayer...) or...

I'd suggest using a standalone digital tv app like Kaffeine or MeTV -- both have built in scanning and probably be easier to go through the discovered services (from memeory, offhand, I don't think either includes the encrypted channels by default). Anyway, testing with one of these standalones should be done anyway to see if you also get purple line in these use cases too.

Quote:


Note: I also have a dual analog tuner card that works ok, however there is alot of fuzz in the picture. (maybe its just the card in the PC?) the signal looks better when plugged directly into the tvs analog tuner.

P.S. this is for comcast cable, so it has both analog and digital channels on it.

In reference to the analog card's reception, sure, it might be picking up noise from somewhere inside your computer and introducing it into the signal....You could try with tvtime to see if you get better results that way -- its postprocessing will generally produces the best output for analog tv reception. Also, if you have any swithes/splitters or anything else, you could try removing them and testing with the cable straight into the analog card.

Another issue that crops up from time to time with PCI cards is dust in the PCI slot -- though that usually manifests itself in other nefarious ways then what you have described. Still, as a basic step, you could always take the cards out, blow out any dust and then re-seat them (PITA, but relatively easy enough to do).

I might be helpful if you can capture a screen cap of your purple line issue and post it somewhere for others to have a look see.
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post #3 of 26 Old 03-29-2012, 02:07 PM
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I would also suggest trying an antenna and scan and play OTA channels. This would help narrow down what the problem is.

You may also be pleasantly surprised at the high quality OTA HDTV is, compared to the compressed signal of cable.
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post #4 of 26 Old 03-29-2012, 02:24 PM - Thread Starter
 
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thank you for the comprehensive reply. Yes, the purple lines is only for the digital. I only have the cable split outside where it comes into the house. I have installed kaffeine, however when i try to scan it says "No available device found" but it does seem to "see" the card. Me TV doesn't seem to work with my card, says no DVB devices found.
I will try to post a picture if i can figure out how to do it. I will also see if i can pickup any channels OTA, i live on the edge of reception, so unless they upped the power, it will be iffy, but it is a good idea to eliminate things.
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post #5 of 26 Old 03-29-2012, 02:27 PM
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MythTV will keep the card occupied, and then no other program can use it. You will need to stop the MythTV frontend and backend first. How you do that depends on which Linux distro you are using
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post #6 of 26 Old 03-29-2012, 02:38 PM
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You can use mplayer to play the channels, by first putting a copy of the channels.conf file in the hidden ~/.mplayer folder in your home directory. It will then play the first channel in the list when you enter this command:
Code:
mplayer dvb://
You can specify a channel by using the name in the channels.conf file, usually the station call letters:
Code:
mplayer dvb://WTMJ-DT
This is playing them without any hardware acceleration, but it is just to test.

Edit: If you have a nVidia card, use vdpau:
Code:
mplayer -vo vdpau dvb://
I have a Radeon card, so I found this works ok for me:
Code:
mplayer -vo gl2 dvb://
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post #7 of 26 Old 03-29-2012, 03:28 PM - Thread Starter
 
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Ok, kaffeine is working! And so is the QAM, it's looking gorgeous. So now, a couple things.
1) how To export kaffeine scan channels to channels.conf? So I can try mplayer
2) some channels are choppy, seemingly due to processor speed. Might mplayer do better? vLC?
3) who knows the magic command line for vlc and the tuner card?
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post #8 of 26 Old 03-29-2012, 03:33 PM - Thread Starter
 
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Oh, also, I am not getting sound in kaffeine... Any tips for this?
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post #9 of 26 Old 03-29-2012, 04:12 PM
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It looks like w_scan is the latest and greatest scanning application. It can be used to make channel files for MythTV/mplayer, Kaffeine and Xine. To make a regular channels.conf file, US terrestrial (OTA), I used this command:
Code:
w_scan -o 7 -fa -A1 -cUS -X > channels.conf
To make one for Kaffeine:
Code:
w_scan -cUS -k > kaffeine.channels.conf
For cable, something like this:
Code:
w_scan -o 7 -fa -A2 -cUS -X > channels.conf
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post #10 of 26 Old 03-29-2012, 04:15 PM - Thread Starter
 
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Cool. I'll try it.
I also found this to try to improve the video in kaffeine. http://ubuntuforums.org/showthread.php?t=1520004
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post #11 of 26 Old 03-29-2012, 09:04 PM
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Quote:
Originally Posted by waterhead View Post

It looks like w_scan is the latest and greatest scanning application.

Actually, the newest is dvbv5-scan ... but meh, they all work, so to each there own
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post #12 of 26 Old 03-29-2012, 09:32 PM
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Quote:
Originally Posted by CityK View Post

Actually, the newest is dvbv5-scan ... but meh, they all work, so to each there own

Thanks, but I don't see that in my distro's repository. I could install from source, but I want to give solutions that are newbie friendly.
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post #13 of 26 Old 03-29-2012, 09:34 PM
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Originally Posted by bowser17 View Post

Ok, kaffeine is working! And so is the QAM, it's looking gorgeous.

Good to read. Hopefully you can resolve the issue that is occuring with use with myth

Quote:


So now, a couple things.
1) how To export kaffeine scan channels to channels.conf?

unfortunately I don't think there is such facility ... in the older, v3, of kaffeine, there used to be an app to convert channels.conf to kaffeine, and there might have been something to go the other way but I don't recall. v4 uses a completely different format for its channel info

Quote:


So I can try mplayer
2) some channels are choppy, seemingly due to processor speed. Might mplayer do better? vLC?

possibly if you pass the right commands, and/or if you offload decoding or what not ... here's a funny tidbit though: in my last OS install I ended up doing (who knows what) something that caused kaffeine to stutter. Could never figure it out. MeTV on the other hand worked beautifully. On my latest install, Kaffeine is back to working perfectly. MeTV on the other hand now stutters. Go figure -- both are using the exact same backend (xine), and its not a question of buffers. Maybe some day I'll try to figure this oddity out, but I'm not particularly motivated in doing so ... anyway, YMMV

Quote:


3) who knows the magic command line for vlc and the tuner card?

Sorry, I don't use vlc very often and don't have it installed currently. Offhand I think its similar to xine and mplayer ... for the most basic use, try "vlc dvb://" which likely would open the first/last_used channel in its channel config .
Have a look here http://www.linuxtv.org/wiki/index.php/VLC_media_player and follow the links to try to find some more advanced usage and options.
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post #14 of 26 Old 03-29-2012, 09:50 PM
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Originally Posted by waterhead View Post

Thanks, but I don't see that in my distro's repository.

Its included in v4l-utils (ugh-- this makes me annoyed!!! but anyway) ... most distro's package v4l-utils ... you'd have to see if the version packaged includes the new toolsuite (http://www.linuxtv.org/wiki/index.php/DVBv5_Tools) ... though, its quite possible that, even if the v4l-utils package available for your distro is brand spanking new, the package manager may have (quite logically) said "what's this -- dvb5 tools -- in v4l-utils??" and stripped them out before releasing the package. I don't know, but could see how this may end up occurring...in which case (which, while just typing, unintentionally came out as chase ... freudian slip?) would mean you'd have to track down some other package for the dvb5 tools .... which no doubt will end up, just to further add to the confusion, being called dvb5 utilities or such by a number of distros that, for whatever unknown reason, just can't seem to call a package what its called in the first place, but instead, prefer to go about and create their own name for it (smashes head on keyboard repeatedly )

Quote:


I could install from source, but I want to give solutions that are newbie friendly.

very reasonable.
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post #15 of 26 Old 03-30-2012, 03:02 PM
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Quote:
Originally Posted by bowser17 View Post

I will also see if i can pickup any channels OTA, i live on the edge of reception, so unless they upped the power, it will be iffy, but it is a good idea to eliminate things.

If you live within 30 miles of the towers, 1 Sale A Day has this Winegard antenna for $19.99 (free shipping):

http://www.winegard.com/freevision/index.php

I can't put a direct link to the deal, because you have to be a member and login to see it. But here's the site:

http://1saleaday.com/

You need to click the "Flash Deals" tab to see it. It is a timed sale, and there are only 6 hours left, as of 5 PM Central time.

I purchased the same antenna from them last week, and it just came today. I paid the same price, but also $5 shipping. I live within 20 miles of the broadcast antennas, and I need to mount my antenna outside. This antenna seems no different, but it is much smaller than my roof antenna (and cheaper).
LL
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post #16 of 26 Old 03-31-2012, 09:05 AM - Thread Starter
 
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Guys, thank you so much for all the tips. I am working away over here and hope to post some results and my own findings in the upcoming days
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post #17 of 26 Old 03-31-2012, 09:18 AM
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Since it seems to be a MythTV problem, have you tried adjusting the playback settings?

Go to :
Setup-->TV Settings-->Playback

The third page, "Playback Profiles", the first setting "Current Video Playback Profile". Use one of the VDPAU settings for a nVidia card. Try them all, to see if one works better than the other.
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post #18 of 26 Old 03-31-2012, 09:46 AM
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Solution for vertical purple lines in mythtv-

http://www.mythtvtalk.com/purple-lin...hannels-15142/

Quote:


solved it. just change the playback encoder. select anything but libmpg2. it seems to be this decoder who is in trouble.

The playback encoder option is in MythTV's setup menu

Also

http://code.mythtv.org/trac/ticket/10110
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post #19 of 26 Old 03-31-2012, 01:03 PM
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Quote:
Originally Posted by Rgb View Post

Solution for vertical purple lines in mythtv-

http://www.mythtvtalk.com/purple-lin...hannels-15142/



The playback encoder option is in MythTV's setup menu

Also

http://code.mythtv.org/trac/ticket/10110

Are you sure it isn't the Decoder, not Encoder? With a nVidia card, he should be using the "NVidia VDPAU acceleration" choice.
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post #20 of 26 Old 04-01-2012, 06:37 PM
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Quote:
Originally Posted by waterhead View Post

Are you sure it isn't the Decoder, not Encoder? With a nVidia card, he should be using the "NVidia VDPAU acceleration" choice.

Yes, I believe it is Decoder in the front end Setup- I was just quoting the reference
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post #21 of 26 Old 04-03-2012, 05:50 PM - Thread Starter
 
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here is the purple lines seen from Myth when trying to watch QAM.
Any suggestions on what database entries need to be modified?
LL
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post #22 of 26 Old 04-03-2012, 08:16 PM
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Quote:
Originally Posted by bowser17 View Post

here is the purple lines seen from Myth when trying to watch QAM.
Any suggestions on what database entries need to be modified?

We already covered that.

Quote:
Originally Posted by Rgb View Post

Solution for vertical purple lines in mythtv-

http://www.mythtvtalk.com/purple-lin...hannels-15142/



The playback encoder option is in MythTV's setup menu

Also

http://code.mythtv.org/trac/ticket/10110

Quote:
Originally Posted by waterhead View Post

Are you sure it isn't the Decoder, not Encoder? With a nVidia card, he should be using the "NVidia VDPAU acceleration" choice.

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post #23 of 26 Old 04-04-2012, 07:32 AM
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Quote:
Originally Posted by bowser17 View Post

here is the purple lines seen from Myth when trying to watch QAM.
Any suggestions on what database entries need to be modified?

Googling "mythtv decoder option" yields

http://www.mythtv.org/wiki/Playback_...lable_Settings

Quote:


Decoder
This defines what library MythTV will use to decode the video, be it software (nuppeldecoder, ffmpeg, libmpeg2), or hardware assisted (ivtv/pvr350, xvmc, mac, via-xvmc).

Try ffmpeg
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post #24 of 26 Old 04-04-2012, 05:32 PM - Thread Starter
 
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THANKYOU!!!! sorry i missed the instruction before, i didn't see all of the configuration pages for myth frontend. now its looking SWEET
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post #25 of 26 Old 04-04-2012, 08:51 PM
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Good to hear. What decoder did you end up using?
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post #26 of 26 Old 04-05-2012, 07:00 AM - Thread Starter
 
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I used the standard ffmpeg & XVideo decoder. For other newbies, this is configured in the frontend (I was focused on the backend configuration). Utilities/Setup->Setup->TV Settings->Playback I wonder why the default is the not recommended decoder. Maybe its just not recommended for my system. Anyways, thanks again!
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