Horizontal video clipping

[maqo]

When viewing live TV (using software encoding) or making recordings using MPEG-2 format, I get choppy video / horizontal bars of corruption (not interlacing) that looks like the video card or system bus can't keep up with the video and is dropping info. Previous MPEG-2 recordings (from another machine) look just fine, so it doesn't seem to be a decoder problem (but maybe a problem with tuning / encoding / playing at the same time?).

When I change to Windows Media, it looks fine. Is this due to WMV using a lower bitrate (and therefore requiring less bandwidth), or possibly a hardware problem? I'm using an old 32 meg GF256 card that is significantly underpowered compared to the Radeon 9700 Pro in my other machine.

I don't imagine that my base hardware is a problem, it's an Athlon XP 2200+ running on an MSI KT266A board, 512 megs PC100, latest 4-in-1, latest WinTV, and SS 3.3.

I was able to record at 720x480, 5mbps bitrate, MPEG-2, software encoding on a different machine...the only major difference was a faster CPU, better video card, and NForce2 chipset instead of KT266A.

Does anyone have any suggestions? Many thanks in advance!

(PS, I can't post a screenshot since it's a really transient effect. In addition, if I view by pausing and unpausing very quickly repeatedly the problem goes away...which makes it seem like it's a bandwidth problem--either over the PCI bus from the TV card or over the AGP bus from the old video card)

[RobertH]

on the machine you are expierincing this with try dropping the refresh rate on the monitor to 60hz (and if it is an nvidia card use the nvidia control panel to lock the directx refresh rates to 60hz) and then change the resolution to something lower than your normal (or use true fullscreen mode)

You should also look into using a 3rd party mpeg decoder on the system as this will enable hardware acceleration and gets rid of most of the tearing issues with the frame rate not keeping up. you may also want to check your video drivers and make sure that vertical sync (vsync) is disabled if it is disabled and you are still seeing the tearing try enabling it and seeing if this helps. if you still get the artifacts after attempting all this then the video card is not going to be able to handle delivering the video at a rate needed to display livetv.

[maqo]

BTW, this is the best screen capture I could make...the tearing is so fast it's hard to catch it! I tried the Nvidia drivers, but the only place I could find anything related to vsync was under the OpenGL section.

I had thought the encoder might make a difference, so I installed PowerDVD (as I had on my other machine), but I don't see any other options for encoders, still just "default." Am I maybe missing something?

Update: I also noticed that live TV with high quality WMV looks fine, but if I am recording and watching live TV I get very minimal occasional tearing...would this still be a video card issue or <gasp>, some kind of hard drive bandwidth issue?

[RobertH]

power dvd doesnt provide a supported codec these are currently the only supported codecs:
- NVIDIA Video Decoder
- ATI(Cyberlink Video/SP Decoder)
- Sonic Cinemaster DS Video Decoder
- Nero DVD Decoder
- DVD Express Video Decoder
- Elecard MPEG2 Video Decoder
- InterVideo NonCSS Video Decoder for Hauppauge
- Ligos MPEG Video Decoder

the harddrive in most systems is running at atleast 16MB/s so you should be able to pull it off. you might want to look at your cpu usage as well and turn of antialiasing/ansiotropic filtering and see if they make any difference. the problem is going to likely be the geforce256 card i dont think it has the internal bandwidth/graphics capabilities to keep up with the overhead of doing the video the way snapstream does it (using dx9 interfaces)

[maqo]

I've had a sneaking suspicion all along that this would be a problem, I just never like throwing out working hardware especially since the GF256 has a tv-out. A new Geforce FX5200 is already on its way, so I'll be sure to post whether or not that resolves it (I'll be surprised if not!)

On a related note, does anyone have any idea what applications the Ligos decoder might come with? I seem to remember seeing it installed as part of something else awhile back on another system, but certainly don't want to go through every program/game I own to try it!

Does anyone have any experience/thoughts on the Nero / Ligos decoders compared to the Snapstream native? (do they roll their own, btw?)

Regards,
M

[RobertH]

off hand it comes with easycd 6 delux (one with dvd software) and several video editing programs (they will usually display a logo similar to the following attachment)

on mine i have the nero decoder (comes with nero6 pro) and ligos(easy cd6) and the ligos decoder blows, it is normally the default in wmp9 and it will cause sync errors up the wazoo, the nero decoder causes an application fault when i try it for somereason so i cant say on that. from what i have seen as good decoders are the nvdvd ones (especially for nvidia cards as it really uses their hardware acclereration) and for pvr owners the hauppauge/intervideo (basically the same one that comes with windvd 4 or 5)

snapstream has its own decoder it is the one called default, it is good for low res captures but stinks for highres/bitrates

[maqo]

According to Nvidia's website NVDVD 2.0 doesn't support the AC97 audio codec that most motherboards with onboard audio use.

Does anyone have any experience using NVDVD and AC97 audio?

[RobertH]

yeah i use it with my 1.8 system it has a via ac97 audio controller on it (even supports using spdif/multi speaker, although ive never tried with nvdvd) I use powerdvd for computer dvd playback, or my JVC shelf system for tv viewing. using it with snapstream does not matter because snapstream only uses the video decoder not the audio decoder.

[maqo]

Just as I was afraid of, moving from a GF 256 to a GF FX 5200 did not alleviate the problem (indeed, the fact that the corruption shows up in recordings and not just live TV while old recordings from another system looked fine made me doubt a video card issue).

I've included a slightly better capture that demonstrates the problem (not the interlacing, this looks fine on a TV). I'm quickly running out of things to try, as the only differences between this system and another one that works flawlessly would be the chipset (KT266A vs Nforce2), memory (PC100 vs PC3200), and video card (GF FX 5200 vs Radeon 9700 Pro).

It really seems as if the Hauppauge capture card is simply not able to push video across the system bus quickly enough without dropping some data. I'm tempted to try a PVR 250 in the hopes that hardware encoding will clear it up, but for that price I could just move to another Nforce2 board, including DDR memory!

Are third party decoders also responsible for the encoding, or is the encoding always done by Snapstream?

Does anyone have a suggestion for what I might be missing? Many thanks!

[ynnek888]

ocasionally, I see this problem too on my TV.. I just assummed that it was the PVR-250's way of dealing with more data than the bitrate can handle.. ie, instead of pixelating, it has that wierd tearing affect. but I could be wrong? ( i record at 4 megabits)

I use a Shuttle SSG51, 512 megs 333 mhz mem, celeron 2.4, FX5200 (64 meg if that makes a difference) svid out, PVR-250, WD with 8 gig cache, Win 2k Pro, onboard audio, The bundle codec that came with the pvr-250, and snapstream v3.2

I rarely notice/rarely happens so I haven't bothered to change anything.


One odd thing, I just about never get stutters or skipped frames.. but the opening title scene of "Crank Yankers" when they fly thru the city always seems to skip and stutter.. Thats the only show that does it..

I'll try fiddling with Vsync.

[RobertH]

tearing with the top of the picture not matching with the bottom of the picture are normally caused by the video card not being able to properly keep the video in sync with the audio or the vsync rate on the video card and as a result will cause a buffer flip (video is drawn to 2-3 seperate buffers, one of wich is displayed on the screen while the "back" buffers are drawn onto, when the back buffer is ready or a vsync is triggered the back buffer is swapped with the front buffer and the process repeats) the flip during an incomplete write is noticed as horizontal tearing of the image (top not syncing with bottom), to fix this one can try using true fullscreen (assuming you arent using a vivo/aiw card) or by dropping the refresh rate of the monitor down to 60hz, you may also be able to try toggling the vsync/buffer settings on your video device. Some have also noted that turning off anti aliasing and ansiotropic filtering solved the problem as well.

[RobertH]

was trying to explain the diff, i know that is definately corruption especailly since it is in the same spot in both captures, probably faulty hardware or the via southbridge problem

[maqo]

I think it was just coincidence that the corruption showed up in the same place in both captures, typically it shows up all over the screen at varying times (but seemingly only during increased motion, not static scenes).

I tried a stick of PC3200 RAM to no avail, so evidence seems to be pointing more and more to the chipset / motherboard (although I have a friend running Windows Media Center with this motherboard with no problem, although he is using hardware encoding; I would imagine it puts a similar strain on the PCI bus as Snapstream).

I've played around with various BIOS settings (PCI Delay Transaction, PCI Latency Timer, PCI IDE BusMaster) but they don't seem to make a difference. I suppose it's possible that I somehow damaged my capture card in transit from one machine to the other, but I could be playing this game forever.

What is the southbridge issue with VIA boards? (and/or a fix?)

Has anyone successfully used a KT266A board with the Hauppauge WinTV PCI (software encoding)? In addition, does anyone have a good download link to the PCI latency patch? Most links I've found are either broken or for beta versions. Many thanks!

[maqo]

I made sure to update the BIOS / drivers to the current versions (from MSI's site using Live Update 3). I still fail to see how it could be an AGP issue, however, since simply recording (without viewing) in MPEG format and playing back on another network-connected machine (to isolate the video subsystem) results in the same corruption...recording straight to disk without viewing in real time should not involve the AGP bus at all, right?

I have also tried putting the card in each of the 6 PCI slots on the motherboard, although I did not do a complete driver uninstall / hwclear after each iteration...

[RobertH]

there is a known problem with a large quantity of via (specifically those right before and directly after the kt266 chipset) where there is severe data corruption going across the southbridge on the system, often caused by a soundblaster live!/audigy1. it often shows up as the system reporting damaged files/being able to not boot or disk errors in the event log (eventvwr.exe) the issue can also occur with other devices that will be doing a large number of DMA transfers like raid controllers, video capture devices, and other high-bandwidth devices.

the latency timer patch fixes the issue (as will some bios updates) for some machines but Ive seen a few where nothing will fix the issue short of getting a new motherboard. The problems also occur more frequently with overclocked systems, but that is a given. theres lots about the via corruption issue on the internet, just search google with via corruption and look at all the hits. although there isnt "one" specific way to solve the problem, hardware encoders might not see these errors because they are just dumping straight to memory or to disk, with software encoding data will be flying all over the bus with the cpu and memory being under great load.