Artefacts during HD playback

[richardcrowther]

When I play HD recordings I get flickering green or gray lines appear which get worse over time. There are also small off-white squares that appear and stay on the picture and menus. It eventually gets so bad I have to stop playback and restart it. That fixes the problem so I doubt the lines are within the recording. To get the squares off of the menu screens I have to close down Sage and restart the program.

This only occurs with HD. I have no problem with regular TV, DIVX/XVID files or DVD's. I'm using an Athlon 64 3000+ with ATI Radeon 9800 pro graphics with the Catalyst 7.9 drivers. I've tried other video decoders like Nvidea Purevideo but still get the problems. Other system info is below. If anyone else has encountered this I'd really appreciate hearing about it.

Software Version: SageTV V6.3.10 - Java Version: 1.6.0_03 - ATI DTV Wonder Analog AV Capture - Hauppauge WinTV 418 Video Capture - Hauppauge WinTV 418 TS Capture - Video Renderer: VMR9 - MPEG2 and DVD Video Decoder Filter: CyberLink Video/SP Decoder (ATI) - Audio Renderer: Realtek AC97 Audio - MPEG2 Audio Decoder Filter: AC3Filter

[mskitty666]

I too am constantly having problems with HD. I have searched many times on these forums but can't seem to find what causes this problem with HD but not SD. I have an Athlon Xp 64 3.0 Ghz dual core processor and on board graphics. I thought about buying a video card, but my motherboard is an HTPC board that is supposed to handle HD. I have noticed that file fragmentation severely affects my HD recordings. Just earlier I tried to watch several shows recorded in HD and the playback was so poor I had to stop. Sure enough they were heavily fragmented. After defragging the files, playback was immediately improved. I just don't think SageTV is very smart when handling HD and multiple tuners.

[stuckless]

After defragging the files, playback was immediately improved. I just don't think SageTV is very smart when handling HD and multiple tuners

I may be wrong here.... but isn't filesystem fragmentation handled by the OS (more specifically the filesystem driver for the OS)? If so, how would Sage be responsibile of it's files were fragmented? I can certainly see how a fragmented file would have performance issues, but I can't see how Sage would be the culprit here.

I would think that if you are constantly getting fragmeneted files, then I would defrag the filesystem and/or change the filesystem to a one that less prone to fragmentation.

[stuckless]

After some thinking.... It would appear that if sage is recording 2 or more shows at the same time, then the files could (and probably would) become fragmented. The same is true when downloading multiple files at the same time (depending on the download manager used). A simple solution to the Sage "fragmentation" issue would be to copy the file after all tuners have stopped recording. This would reduce the fragmentation in the original file, provided the filesystem would defragemented to begin with.

[Thomas Wischgol]

Make sure your file systems are formatted with 64K blocks. Then fragmentation is not that much of an issue and Sage can handle HD much better. SD actually still works even with 4K blocks; but with HD the performance is too low. I have three tuners in my system (1 HD, 2 SD) and it works perfectly fine even if all three tuners record to the same hard drive and I play back an HD stream from this drive. On top of that you can enable write caching using Microsoft's tool dskcache.exe if your system is battery backed. This way, your system uses write back, not just write through.

Thomas

[mskitty666]

I may be wrong here.... but isn't filesystem fragmentation handled by the OS (more specifically the filesystem driver for the OS)? If so, how would Sage be responsibile of it's files were fragmented? I can certainly see how a fragmented file would have performance issues, but I can't see how Sage would be the culprit here.

It is my understanding that SageTV does not estimate the disk space reqired for a recording file like some of the designated dvrs do. Since I am usually recording two or more shows at a time, this is what causes my fragmentation. I have not been able to find out if this is just aq physical limitation of the hard drive when recording multiple streams. Even if it is a physical limitation, if Sage could be instructed to reserve the space, it would make my daily defrag much more quick and efficient.

I would think that if you are constantly getting fragmeneted files, then I would defrag the filesystem and/or change the filesystem to a one that less prone to fragmentation.

I now have scheduled PerfectDisk to defrag files every day. It just doesn't hel-p much if the defrag has not yet run on the shows I want to see . What file system do you use? I have no experience with Linux so am using WinXP Pro NTFS.

Make sure your file systems are formatted with 64K blocks. Then fragmentation is not that much of an issue and Sage can handle HD much better. SD actually still works even with 4K blocks; but with HD the performance is too low. I have three tuners in my system (1 HD, 2 SD) and it works perfectly fine even if all three tuners record to the same hard drive and I play back an HD stream from this drive.

I have formatted the drive in 64k. I have four tuners, two SD and two HD. Your response is what is making figuring out my problem so difficult. HD playback issues seem to be common problems on this forum as well as many others. For some it works flawlessly and for others not.

On top of that you can enable write caching using Microsoft's tool dskcache.exe if your system is battery backed. This way, your system uses write back, not just write through.

What do you mean if the system is battery backed? And would you mind explaining what write through does? I would like to try this and see if it helps.

[richardcrowther]

Thanks for the ideas guys. I did some work on the system today and completely defragged all my files, the drive formatting was already in 64K blocks.

It hasn't helped the playback though. I'm still getting image break up. It seems to be worse on specific channels. "Lost" plays OK off ABC but "The Office" on NBC is particularly bad. Could this be linked to one type of HD format?

[Slipshod]

Originally Posted by mskitty666

What do you mean if the system is battery backed? And would you mind explaining what write through does? I would like to try this and see if it helps.

Battery-backed= UPS, like an APC or Tripplite.

Write-through caching means that the file being written is cached in memory (in case it's needed later), but is written immediately to the disk.

Write-back means that disk-writes can be cached and deferred, allowing more optimization on the writes as well as higher throughput. It's particularly effective with a RAID-5 array where you take a massive performance penalty if you do partial-strip writes. In your contect, write-back would "reduce fragmentation" in that the fragments themselves would be in larger chunks since the OS wouldn't be focusing on writing to disk as quick as it can.

[Thomas Wischgol]

Originally Posted by richardcrowther

Thanks for the ideas guys. I did some work on the system today and completely defragged all my files, the drive formatting was already in 64K blocks.

It hasn't helped the playback though. I'm still getting image break up. It seems to be worse on specific channels. "Lost" plays OK off ABC but "The Office" on NBC is particularly bad. Could this be linked to one type of HD format?

The format can make a difference. My client in the bedroom only has a GeForce 6200 and it plays 720p content just fine (on a 1360x768 display), but stutters slightly with 1080i content. However, I believe "Lost" is aired in 1080i. You can check it via the detailed info section in Sage where it lists the exact format for that stream.

Assuming you are sure the problem is related to the hard drive and not the graphics card/CPU, I would try switching to write back and see if that helps. Also you can check whether acoustic management is enabled on your system and set to a low noise setting which penalizes performance.

Thomas

EDIT: P.S.: you will need the tool dskcache.exe from Microsoft to enable write back in XP

[richardcrowther]

Thanks for the help. After a lot of playing around I finally got it fixed. Disableing the 3D acceleration sorted it out. I have no idea why though since I would have thought that using the 3D acceleration would have helped out with the processing but I'm spending too much time watching all my HD programs now to worry about that too much.