Debug tip for those that s..ss..sstudder

[sundansx]

Today I discovered a possible debug technique that people might be able to use.

Some people are debugging video playback studdering problems with their sageTV playback. During this debug it is kinda hard to figure out if the studder problem occurs because of a studdering during recording of the video (dropping frames), performance or bugs in the mpeg decoder or directshow path, a bug in sageTV itself, or a disk subsystem limitation.

Playback the studdering video while watching your disk activity. Now press the RW2 or RW (10 or 30 seconds back) button. I noticed that the disk subsystem is idle for almost 30 seconds or more with 512 megs of ram. This is because Windows has buffered a significat portion of the video you just played back in memory. It is like you are playing back from a RAMDrive.

Lets take the first case:
(studder from above case, studder on another system)
Now, if you still see the studdering, you can eliminate a disk subsystem playback limitation. You can try to play the video on another system. If it studders, then you probably have a recording problem. It is likely caused by overloading your processor (easy to check) during recording, a disk speed problem while writing, or a interrupt sharing problem with your encoder card

second case:
(studder from firstcase, no studder on another system)
If you still seeing studdering using the rewind trick but dont see it on another system, you have a problem with your playback subsystem on your Sage tv system. This can be caused by a crappy video card that can't keep up, a mess in your direct show setup (you might want to avoid codec packs), video card driver problems, software decoder bugs or problems. Your disk subsystem and hardward encoder subsystem are probably fine.

third case:
(no studder from first case, no studder on another system)
If you don't see your video studder when you rewind and you see it when the video playback reaches the point you previously played to (you can see your harddrive activity start back up) you probably have a disk subsystem problem. Could be caused by a drive running in non-dma mode, a disk handling lots of parity errors on the interface cable, or the filesystem structure cant keep up. To shotgun these problems, (in order with respective to above) check that your hd is setup to use UDMA33 or UDMAmode in the device manager, replace your harddrive (HD) cable (remember, never attach a single drive to the middle connector on parallel hd cable, always use the end connector) or HD with another, or reformat your HD with 64K blocks. On the last one, you might have to use the commandline format command under older Windows versions (type 'format /?' for template).

forth case:
(no studder from first case, studder on another system).
Both of your computers suck. The 80's called, they want their computers back.

hope this helps,
-ck