From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mx1.redhat.com (ext-mx05.extmail.prod.ext.phx2.redhat.com [10.5.110.9]) by int-mx04.intmail.prod.int.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id nACG3mC2020226 for ; Thu, 12 Nov 2009 11:03:48 -0500 Received: from mail-qy0-f185.google.com (mail-qy0-f185.google.com [209.85.221.185]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id nACG3Rur024018 for ; Thu, 12 Nov 2009 11:03:47 -0500 Received: by mail-qy0-f185.google.com with SMTP id 15so93743qyk.23 for ; Thu, 12 Nov 2009 08:03:47 -0800 (PST) Message-ID: <4AFC31DE.6060708@gmail.com> Date: Thu, 12 Nov 2009 17:03:42 +0100 From: Ryan Raasch MIME-Version: 1.0 To: Shun-Yu Chang References: <4AFC127F.4070300@gmail.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: V4L-Linux Subject: Re: Camera preview, thin lines in the frames List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: video4linux-list-bounces@redhat.com Errors-To: video4linux-list-bounces@redhat.com List-ID: Shun-Yu Chang wrote: > > > On Thu, Nov 12, 2009 at 9:49 PM, Ryan Raasch > 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 > > > > 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... > > > 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)? > 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. > > > > > -- video4linux-list mailing list Unsubscribe mailto:video4linux-list-request@redhat.com?subject=unsubscribe https://www.redhat.com/mailman/listinfo/video4linux-list