Re: Camera preview, thin lines in the frames
- Date: Thu, 12 Nov 2009 23:54:24 +0800
- From: Shun-Yu Chang <shunyu.chang@xxxxxxxxx>
- Subject: Re: Camera preview, thin lines in the frames
On Thu, Nov 12, 2009 at 9:49 PM, Ryan Raasch <ryan.raasch@xxxxxxxxx> 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
>> in the frames.
>> I still have no idea how to describe this exactly. It's like the images
>> shows here,
> 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
> 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.
I don't quite understand about FIFO levels of the data lines part.
Could give an instruction where I can start to look into?
Thanks for your reply..
> 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.
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