Re: Camera preview, thin lines in the frames
Shun-Yu Chang <[email protected]>
| Newsgroups | gmane.comp.video.video4linux |
|---|---|
| Message-ID | <[email protected]> |
On Fri, Nov 13, 2009 at 12:03 AM, Ryan Raasch <[email protected]> wrote: > > > Shun-Yu Chang wrote: > >> >> >> On Thu, Nov 12, 2009 at 9:49 PM, Ryan Raasch <[email protected]<mailto: >> [email protected]>> wrote: >> >> >> >> Shun-Yu Chang wrote: >> >> Hello, list: >> I am new to v4l2. I am working on integrating a usb camera >> device on >> the beagleboard(Omap3530 dev board). >> Now I met a camera preview issue that is there are thin lines >> coming out >> in the frames. >> I still have no idea how to describe this exactly. It's like >> the images >> shows here, >> http://0xlab.org/~jeremy/camera_preview.html<http://0xlab.org/%7Ejeremy/camera_preview.html> >> <http://0xlab.org/%7Ejeremy/camera_preview.html> >> >> >> >> I have two guesses. One is the jpeg compression ,or is it jpeg? Try >> saving in raw RGB or Ycbcr format and viewing with imagemagick. >> >> >> The raw data I got is yuyv422. I used the mmap way. I tried to convert >> raw data to yuv420 and jpg files both. I used ffmpeg to convert yuv420 >> files to jpg files and I can still see the lines. >> I don't know how to use imagemagick to see yuv files... >> >> >> >> Does this happen in live preview? Maybe write data from camera >> directly to screen to see if happening there. >> >> >> It happens in live preview. So I save the frames directly into files >> to verify. >> >> > But if you save the files, you don't know if the compression is the > problem. You need to visually look on the screen with a magnifying glass or > something... Got your point, I will try to output to the screen without any compression later. > > > >> >> The second would be the FIFO (hadn't worked with omap before) levels >> of the data lines to the processor in the kernel. >> >> Look at the system processor (top) usage to see how much cpu% is >> being used. USB has high overhead. >> >> the top command shows >> PID CPU% S #THR VSS RSS UID Name >> 1012 56% R 1 55000K 54468K root capture_test >> 241 40% R 1 0K 0K root pdflush >> [....Omit, others are 0%. .....] >> After grabing the first 100 frames to files, capture_test exits. >> >> > Looks pretty busy to me. Maybe you could kill the pdflush, don't save to > files, and look at the display with a magnifying glass. > > > I don't quite understand about FIFO levels of the data lines part. >> Could give an instruction where I can start to look into? >> >> > It probrably has dma priorities. So if other drivers in the system > (network, usb, display, etc.) use a lot of cpu time, the camera dma might be > delayed. > > > Are you saving the files over network (nfs)? No, they are saved to files on the target, then transferred back to my laptop. > > Thanks for your reply.. >> >> Regards, >> -Jeremy >> >> >> >> >> Regards, >> Ryan >> >> >> I modified capture.c sample to save the frames to picture >> files. So in >> my guess, the problem is not in userspace. And this is not >> happen on my >> laptop with the usb camera. >> Could anybody give me a clue ? Any one would be thankful. >> >> >> >> >> >> -- Regards, -Jeremy -- video4linux-list mailing list Unsubscribe mailto:[email protected]?subject=unsubscribe https://www.redhat.com/mailman/listinfo/video4linux-list