Webcam Pulse Detector • Hacker News Board

Re: Webcam Pulse Detector

#81

Post by mkopinsky » Tue, Apr 16, 2013, 8:59 PM UTC

jerich wrote: post #79

mkopinsky wrote: post #77

Earlier quoted context omitted.

Is that noise inherent to film? Do webcams have the same noise?

The green channel has the least noise for Bayer-sensor digital cameras (which is almost all of them). 50% of the sensor sites are green (25% each for red and blue), so there is more signal given the same amount of noise.

Why do they make them like that? Why not make the sensors 33/33/33?

Re: Webcam Pulse Detector

#82

Post by jerich » Tue, Apr 16, 2013, 9:38 PM UTC

mkopinsky wrote: post #81

jerich wrote: post #79

Earlier quoted context omitted.

The green channel has the least noise for Bayer-sensor digital cameras (which is almost all of them). 50% of the sensor sites are green (25% each for red and blue), so there is more signal given the same amount of noise.

Why do they make them like that? Why not make the sensors 33/33/33?

From Wikipedia on the Bayer Filter: "Bryce Bayer's patent (U.S. Patent No. 3,971,065) in 1976 called the green photosensors luminance-sensitive elements and the red and blue ones chrominance-sensitive elements. He used twice as many green elements as red or blue to mimic the physiology of the human eye. The luminance perception of the human retina uses M and L cone cells combined, during daylight vision, which are most sensitive to green light."

The Foveon sensor does sample RGB at every pixel by using 3 layers, but it is only used in a few cameras.

Re: Webcam Pulse Detector

#83

Post by hokkos » Tue, Apr 16, 2013, 10:56 PM UTC

hac wrote: post #68

I've gotten this far trying to install this on Lion: brew install gfortran sudo easy_install scipy sudo port install opencv +python27 export PYTHONPATH=/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/:$PYTHONPATH wget http://openmdao.org/releases/0.5.0/go-openmdao.py sudo python ./go-openmdao.py cd ~/Downloads/webcam-pulse-detector-master/openmdao-0.5.0 . bin/activate cd ~/Down…

I got it working in ML with :

brew upgrade

brew tap homebrew/science

brew install opencv

brew install gfortran

sudo easy_install scipy

mkdir OpenMDAO

cd OpenMDAO/

brew install wget

wget http://openmdao.org/releases/0.5.0/go-openmdao.py

export PYTHONPATH=/usr/local/Cellar/opencv/2.4.4a/lib/python2.7/site-packages/:/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/:/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/:$PYTHONPATH

sudo python ./go-openmdao.py

cd openmdao-0.5.0/

. bin/activate

#get the project in webcam-pulse-detector I used the github app

cd ../../webcam-pulse-detector/

python get_pulse.py

Re: Webcam Pulse Detector

#84

Post by shabble » Wed, Apr 17, 2013, 12:52 AM UTC

mkopinsky wrote: post #67

evan_ wrote: post #65

Earlier quoted context omitted.

You could get better results with a Bluetooth pulse monitor.

That probably requires wearing something, potentially on your finger. Webcam is much less intrusive.

Turns out that the fingertip pulse oximeter[1] I have works surprisingly well on a toe.

Probably only applicable if you work from home though.

[1] http://www.nonin.com/OEMSolutions/WristOx2-Model-3150-OEM

Re: Webcam Pulse Detector

#85

Post by indubitably » Wed, Apr 17, 2013, 5:31 PM UTC

hac wrote: post #68

I've gotten this far trying to install this on Lion: brew install gfortran sudo easy_install scipy sudo port install opencv +python27 export PYTHONPATH=/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/:$PYTHONPATH wget http://openmdao.org/releases/0.5.0/go-openmdao.py sudo python ./go-openmdao.py cd ~/Downloads/webcam-pulse-detector-master/openmdao-0.5.0 . bin/activate cd ~/Down…

> brew install gfortran

gulp. fortran?