use maemo camera by python

Question

I wrote a simple program for Maemo by Python to check some pixel's color every time that my function is called. But this function runs very slowly (3-5 seconds each call). Is there any faster way to do this?

import Image
import os
import sys

# sen_pos = (pixel_x, pixel_y)
def sen(sen_pos):
    os.system("gst-launch v4l2src device=/dev/video0 num-buffers=1 ! ffmpegcolorspace ! jpegenc ! filesink location=cam.jpg")
    frame = Image.open("cam.jpg")
    col = frame.getpixel((sen_pos[0], sen_pos[1]))
    avecol = sum(col) / len(col)
    if avecol > 127:
        return "white"
    elif avecol < 127:
        return "black"
    return None

Without being at all familiar with gstreamer, is the colorspace conversion really necessary? Also, tuning the quality parameter to `jpegenc` may help. — Michael Mior, Oct 27 '11 at 19:10

score 2 · Accepted Answer · edited Aug 17 '12 at 06:29

2

Calling an external program via os.system is likely what's taking the time.

Try using GStreamer Python Bindings instead and keeping the video object around between calls. The docs for Videomixer may help.

edited Aug 17 '12 at 06:29

Jason Sundram

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answered Nov 25 '11 at 12:04

George

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score 1 · Answer 2 · edited Aug 17 '12 at 06:27

1

As George says, you may be incurring overhead in a system call but I suspect the getpixel() call. PIL's getpixel() is notoriously slow. Instead load() the image and then loop through -- that should be faster.

edited Aug 17 '12 at 06:27

Jason Sundram

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answered Dec 05 '11 at 17:18

Aloo Gobi

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use maemo camera by python

2 Answers2