Author Topic: TV image quality issue  (Read 2145 times)

leonja

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TV image quality issue
« on: November 16, 2007, 03:08:05 pm »
Hi guys,
I can watch TV in LMCE and rewind or fast forward in MythTV, but the image quality, although acceptable, is noticeably lower than what I get using the direct cable connection to my LCD TV.  My capture card is a Hauppauge PVR-150 and my onboard video card is an Nvidia FX 5700.  Image quality when playing ripped DVDs or navigating the GUI is perfect.  How can I improve the image from MythTV so that I don't feel I had to give up something in order to use LMCE?  I have been searching the mythtv setup screens but I can't find something that will improve the image. 

Could it be TV image resolution set too low? 
Could it be MPEG-2 compression set too high? 
How are these things set? 

I haven't changed any settings in Mythtv from the default LMCE installation aside from setting up the PVR-150 tuner1 connection to the cable supplier.

Please help,
Jaime
Selectron 42 inch LCD TV
AMD Athlon 2800+ on MSI K7N Motherboard
2x512MB DDR400 RAM
PNY Nvidia FX 5700 AGP video card
Hauppauge PVR-150 MCE capture card
Integrated Realtek 5.1 audio

aurum

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Re: TV image quality issue
« Reply #1 on: November 22, 2007, 09:45:05 am »
/*
I can watch TV in LMCE and rewind or fast forward in MythTV, but the image quality, although acceptable, is noticeably lower than what I get using the direct cable connection to my LCD TV.  My capture card is a Hauppauge PVR-150 and my onboard video card is an Nvidia FX 5700.  Image quality when playing ripped DVDs or navigating the GUI is perfect.  How can I improve the image from MythTV so that I don't feel I had to give up something in order to use LMCE?  I have been searching the mythtv setup screens but I can't find something that will improve the image. 
*/

all analog pctv card have a some "quality".
u can do 2 thing:

1. buy a digital tuner
2. download the tv show from ur favorite torrent site. the rss-feed is very confortable ;) with azureus u can get sms or email if new part is downloaded.

totallymaxed

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Re: TV image quality issue
« Reply #2 on: November 22, 2007, 10:03:25 am »
Hi guys,
I can watch TV in LMCE and rewind or fast forward in MythTV, but the image quality, although acceptable, is noticeably lower than what I get using the direct cable connection to my LCD TV.  My capture card is a Hauppauge PVR-150 and my onboard video card is an Nvidia FX 5700.  Image quality when playing ripped DVDs or navigating the GUI is perfect.  How can I improve the image from MythTV so that I don't feel I had to give up something in order to use LMCE?  I have been searching the mythtv setup screens but I can't find something that will improve the image. 

Could it be TV image resolution set too low? 
Could it be MPEG-2 compression set too high? 
How are these things set? 

I haven't changed any settings in Mythtv from the default LMCE installation aside from setting up the PVR-150 tuner1 connection to the cable supplier.

Please help,
Jaime


I assume you are using the PVR150 to grab TV from an external source. If thats so then your just seeing the quality loss when your PVR150 digitises the video. There maybe some parameters you can adjust to improve things inside Myth but I am not familiar with it enough to help you there.

If on the other hand you are comparing the "off air" picture your TV receives to the same signal delivered via the PVR150 TV encoder then I would say you are seeing a quality possibly more to do with how you are connecting your PVR150 to your TV.
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aurum

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Re: TV image quality issue
« Reply #3 on: November 22, 2007, 11:04:28 am »

[/quote]

I assume you are using the PVR150 to grab TV from an external source. If thats so then your just seeing the quality loss when your PVR150 digitises the video. There maybe some parameters you can adjust to improve things inside Myth but I am not familiar with it enough to help you there.

If on the other hand you are comparing the "off air" picture your TV receives to the same signal delivered via the PVR150 TV encoder then I would say you are seeing a quality possibly more to do with how you are connecting your PVR150 to your TV.
[/quote]

http://www.hauppauge.com/pages/products/data_pvr150.html

/*
MPEG record specifications:
 
 MPEG2 record datarates:
2MBit/sec, 4MBit/sec, 6Mbit/sec, 8Mbit/sec, 12Mbit/sec.
Selections for DVD Standard play (8MBitsec), DVD Long Play (4MBit/sec) and DVD Extra Long Play (2.5MBit/sec)
 
 NTSC format* at 29.97fps: Full D1: 720x480, MPEG1: 352x240
 
 PAL format* at 25fps: Full D1: 720x576, MPEG1: 352x288
 
 Audio capture formats: 32/44.1/48 KHz, 16bit stereo, 192/224/384Kbits/sec
 
 Video digitizer: 10 bits
Chroma sampling: YUV 4:2:2
Four line adaptive comb filter for both NTSC and PAL to remove dot crawl
Fast video locking for security camera applications
 
*/

so.. the max resolution is 720x576, but in the real life, the pal resolution is 768x576. other big weakness : Video digitizer: 10 bits. for good quality grabing at least 12bit, but 16bit need.

some 1000 years old bt848 pctv card outpreform this values...

leonja

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Re: TV image quality issue
« Reply #4 on: November 23, 2007, 05:53:53 am »
totallymaxed,
Yes, I am comparing the cable tv signal when fed directly from the coaxial cable to the antenna port in the tv, to the image when playing Mythtv using my PVR-150 capture card fed from the same cable tv signal.  The coaxial cable is connected to the PVR-150 antenna port and the output is fed to the tv via the vga port at 1280x768 resolution.  The image when playing DVDs is very good but not as good when watching Mythtv.

aurum
I live in Panama, so the tv standard is NTSC.  Do you know how to configure the different mpeg-2 recording data rates in Mythtv?  My suspicion is that Mythtv may be using a low data rate and thus the quality of the image is suffering.

Thank you both for your comments and support.
Jaime
Selectron 42 inch LCD TV
AMD Athlon 2800+ on MSI K7N Motherboard
2x512MB DDR400 RAM
PNY Nvidia FX 5700 AGP video card
Hauppauge PVR-150 MCE capture card
Integrated Realtek 5.1 audio

aurum

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Re: TV image quality issue
« Reply #5 on: November 23, 2007, 08:18:59 am »

aurum
I live in Panama, so the tv standard is NTSC.  Do you know how to configure the different mpeg-2 recording data rates in Mythtv?  My suspicion is that Mythtv may be using a low data rate and thus the quality of the image is suffering.

[/quote]

u can set different quality recordig profiles in mythtv, then select these profiles for livetv or recording.

the anxious

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Re: TV image quality issue
« Reply #6 on: February 10, 2009, 10:15:32 pm »
well.. i have the same problem.. when using mythtv i get low quality image...but when I look the tv guide and resize the tv screen the image is perfect..
its look likre an problem of image resolution..i don´t know..



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jondecker76

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Re: TV image quality issue
« Reply #7 on: February 10, 2009, 11:01:18 pm »
I've set up my PVR-500 twice. The first time, the image quality was horrible and I was extremey disappointed. I ended up doing a full reinstall at some point, and using the same card the second time the image was just as clear as the original source. This makes me think there is some configuration involved, though I don't know exactly what gave me such different results on the exact same hardware.
I have also found that the s-video input gives me the best results

the anxious

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Re: TV image quality issue
« Reply #8 on: February 11, 2009, 05:51:48 pm »
After trying many connections whitout success, I just have composite imputs to get the signals from my cable provider, the signal is better than others imputs, but I can´t change the channels using the Fiire Chief.. I need to make an IR-Blaster, but I don´t have idea how can I do this.. I will search more to get everything working.
How do yout change channels using the s-video imput? need an IR-Blaster too?

Asus M2N-E-SLI, 2GB Kingston, HD 500GB Seagate, Hauppage PVR-500, Geforce 7300GS, Fiire Chief, Nokia N800, Samsung LN32A330J1 32", HA22, Intermatic Switches, USB UIRT, Xantech 286 double emitter,

krys

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Re: TV image quality issue
« Reply #9 on: February 11, 2009, 06:00:16 pm »
yes, s-video will not carry commands. USBuirt's work well for this

skeptic

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Re: TV image quality issue
« Reply #10 on: February 11, 2009, 06:34:22 pm »
Change the recording profile from the scheduling area within Myth from default to high-quality.  I'm not at home so I can't tell you the screens to go into, but it's there and it makes a pretty big difference. 

I don't remember for sure, but I don't think you can set this from Mythweb.