TV: Horrible picture quality and TV halts after a while (1 Viewer)

[Nicodemuz]

MediaPortal Version: 0.2.3 with SVN from mid/late July
MediaPortal Skin: Blue Wide
Windows Version: Win XP Home SP2
CPU Type: AMD Athlon 2400+
Video Card: NVidia Geforce 5500
1. TV Card: ZapTV Mini
1. TV Card Type: DVB-t
Remote: MCE remote
TV: 46" LCD
TV - HTPC Connection: DVI-to-HDMI, running at 1920x1080@50i

The picture quality is really blurry when compared to other applications like the one provided with the DVB-t adapter.
Replaying the recordings made by MP in another application still yields blurry image quality so it seems to me that MP does something to the received stream, like re-encoding to an inferior rate/format BOTH before showing the image and recording it.
Recordings are also really small, less than 400MB for half an hour of TV but the bitrate of the TV-channel would give me larger recordings - on my Set Top Box recording the same channel for an hour gives me files at approx 1.5GB.

And I am unable to record more than half an hour or watch more than half an hour because the TV halts after between 10 and 30 minutes. Choosing a new channel often gives picture back but not always.

De-interlace is set to None (since I use interlaced signal to TV and the channel received is interlaced).

Picture quality is set to highest for recordings.

Timeshift is set off.


And way around this or do I need to look for another solution to get picture quality?
On a 46" LCD 2 meters away it is very obvious that the quality is bad.

 

[ronilse]

Hi,
Never had problem with this, please attach mediaportal.log (installation path\Team MediaPortal\MediaPortal\log) to your post & tell us what card (tuner & graphic) you use.

Regards
Roy

 

[Nicodemuz]

I will do so when I get home and get some time at the TV when no one is watching...

More information:
DVB-t rceiver used: http://www.club3d.nl/index.php/products/zaptv/item/14
Signal strength and quality is always 100% independent of application used - I think that the halting TV could be due to not-so-good reception and a sensitive DVB-t receiver. However, before buying this one I borrowed a friends DVB-t receiver (also a small USB stick) and had no problems but can't say I tested it more than a few minutes...
i have considered going back with the receiver to the reseller and try another one but the alternatives they had cost twice as much.

Regarding the blurry image:
I just read that the mpeg stream from the air is rencoded into DVR-MS format to get timeshift support, or did I misunderstand anything?
And that can explain that the image get blurry?

 

[kiesow]

AFAIK there is nothing re-encoded, because DVR-MS is mpeg with additional metadata, see http://en.wikipedia.org/wiki/DVR-MS

 

[Nicodemuz]

I have tried recording with other softwares now and I get the same problem with halted recordings.
I will return the device to the shop and buy another brand.

I think I need to do further studies about picture quality - difficult to switch between different applications fast enough on live streams. It's easy to forget how the picture really was. I haven't tried changing decoder either.
But compared to my Set-Top-Box the image is much blurrier and that box uses SCART to the TV while I use DVI/HDMI from the PC.

Could it be a resolution thing?

The STB produces 720x576 which the TV displays on 1366x768.
From PC I use 1920x1080i to be displayed at 1366x768 (my TV don't support 1366x768@50Hz and running that on 60Hz gives a very jerky playing of movies).

 

[Paranoid Delusion]

From PC I use 1920x1080i to be displayed at 1366x768 (my TV don't support 1366x768@50Hz and running that on 60Hz gives a very jerky playing of movies).

What is the TV's native pc resolution according to the instrution manual, that is the resolution i would use for the best picture quality.

 

[Nicodemuz]

1366x768
But it doesn't support that in 50Hz (or 50i) so I run it at 1920x1080@50i
I have not been able to achieve 1280x720@50p - only 60p - which is why I chose 1920x1080.

But picture quality is amazing at 1366x768@60p if it wasn't for that obvious jerkiness, especially in paning scenes.

 

[Nicodemuz]

By amasing picture quality I didn't mean the TV picture quality...that is still blurry.

I have now switched DVB-t device to another brand and now it doesn't hang/halt within 30 minutes. And I get signal strength and quality values that differ from 100% so this new card seems to behave more as expected.
Recordings work but they get surprisingly small.
Recorded the same show bot in MP and in my STB and the STB produces 70% larger file and I know that the STB records the mpeg2-stream sent over the air.

So to me it seems MP re-encodes before recording, and probably before viewing due to timeshift, and that can explain the blurrier TV-picture when using MP compared to my STB.
Is this the case?
Or is there something else that is the reason?

I have tried several different decoders (MPV, ffdshow, elecard, cyberlink, etc) and with same result. But I have had no postprocessing enabled, maybe that is the key to get same quality as the STB?

Some more playing around have made me to come to the conclusion that at least most of the blurriness is due to de-interlacing (or lack of).
I am currently using ffdshow and enabled de-interlacing in ffdshow video config and got better image quality but none of the choices of de-interlace method gives me the same good picture that I get from my STB. But the difference in quality is less now.

Anyone got any recommendations in the area of de-interlacing?