ipaq 2215 screen 'shear' when playing vids

[jon_n]

Hi,

I don't know if I'm expecting too much of my 2215, but playing video looks awful - during fast moving scenes the screen seems to shear - you can see it redrawing diagonally left to right down the screen. It does this with pretty much any full screen video - mpg via pocketTV, and WMV that I've encoded myself (Using windows media encoder 9 with ~250K bitrate). I've tried the deinterlace settings in WME and they don't make any difference. It also does it with in a window video as well..

It's almost like the refresh rate for the screen is too low, or the ipaq is having problems redrawing the screen quick enough... Other than the shearing, it looks fine, doesn't seem to drop frames etc

Is this normal, is there something up, or are there some tweaks I can make?

Cheers,

Jon

[[email protected]]

I have a 2210 and mine is o.k. I never have had a problem on my IPAQs. I have 5555 and it plays fine too.

[The PocketTV Team]

"Shearing" occurs when the time for displaying a frame is much longer than the screen refresh rate.

It occurs when video playback is slow (low framerate) and is more noticeable when you have fast-moving scenes, because you occasionally end-up seeing parts of two very different frames.

Normally if the framerate is high (i.e. 24-30 fps) you should not see "shearing".

Maybe your device is abnormally slow because of some background task. Try doing a soft-reset.

Also, make sure to play files that have been encoded with parameters optimized for your device. For MPEG, the bitrate should be less than 400 Kbit/sec. Use the Simple Guide for making MPEG files optimized for Pocket PC or Smartphone (http://forum.pocketmovies.net/viewtopic.php?p=3415#3415).

[jeffmd]

low framerates actually prevent shearing, but yesits caused by when a new frame is displayd while the screen is in the middle of refreshing/redrawing the lcd. Not much you can do about it either, its a defect in the low quality video chips in most of todays pocket pc's.

[The PocketTV Team]

> low framerates actually prevent shearing,

not always. if the system is slow then the video player will take a long time to draw each frame frame, it is more likely that the framebuffer will be displayed while it is being drawn by the app, i.e. while it contains part of one frame and part of the next frame.

> but yesits caused by when a new frame is displayd while the screen is in the middle of refreshing/redrawing the lcd.

correct.

> Not much you can do about it either, its a defect in the low quality video chips in most of todays pocket pc's.

I don't think that has to do with the "low quality" of the video chips used by Pocket PC. But it has more to do with the fact that it is not possible for applications to synchronize frame buffer update with the display frequency (i.e. the timing at which the frame buffer is scanned by the video chip and displayed).

Anyway, there's little you can do about that, and it is less noticeable on faster devices.

[Zathras]

Sorry to chime in on this so late.

I found out on the Corecodec PocketMVP forum that the diagonal shearing on the 2200 or probably any pda that is prone to this can be fixed by pre-rotating the movie. Here is the thread:

http://www.corecodec.com/modules.php?op=modload&name=PNphpBB2&file=viewtopic&t=481

I was told my old iPAQ 3900 didn't tear because it had a rotation buffer.

I tried some pre-rotated movies and they play great. No tearing and some related blocking is gone too.

Now I wish I could figure out how to get WM9 to do this. Windows Media Encoder won't let you rotate and Windows Media Player won't play rotated movies correctly. No matter, DivX plays fine.

[The PocketTV Team]

Pre-Rotating does not necessarily work, it depends on the decoder you are using and on the way this decoder accesses the memory. Of course it also depends on the video memory organization on the device.

In the case of PocketTV, pre-rotating the video at encoding time is totally useless, because PocketTV automatically accesses the video memory in the most optimum way regardless of the orientation used when encoding. So pre-rotating the movie will not change the PocketTV performances at all.

PocketMVP does not have this capability the PocketTV has, so pre-rotating the movie with PocketMVP may work with some devices.