Richard J. Prinz

Playing around with Zinc’s streaming entities I looked for a source of streaming data. A never ending streaming source are video streams. So I implemented a very simple Motion JPEG reader using Pharo Smalltalk. It does not use any plugins. Just plain smalltalk and a stock pharo image.

Use your pharos monticello browser to add the following repository and open it.

MCHttpRepository
   location: 'http://www.min.at/prinz/repo/mjpeg'
   user: ''
   password: ''

Update:
Some people have reported hat they cannot load the package into their image. Opening a monticello browser, adding a new http repository with +Repository and pasting the code snippet above and then opening the repository works as expected. Alternatively you can download the package using this link and open it from a local directory repository.

Update 2:
As noted by Sven Van Caekenberghe the mime type for .mcz monticello archives is now set to application/x-monticello in the webserver response. So now there should not be any format errors. Thanks for this hint.

Update 3:
Cédrick Béler modified the source to work under Pharo 7. Thanks for that. The new version can be found in the repo.

It consists of just one class Mjpeg.

| cam |
" Create a new MJPEG stream from a given url "
cam := Mjpeg 
   fromUrl: 'http://218.219.210.174:86/mjpg/video.mjpg?camera=1'.
" Start reading the stream and displaying it in a window "
cam start. 
" Start capturing the stream frame by frame to disk "
cam startCapture: 'c:/temp/test'.
" Returns true if the stream is started (reading or "
" capturing), false otherwise "
cam isRunning.
" Stop reading the stream and close the camera window "
cam stop.
" Stop capturing "
cam stopCapture.

There are two example class methods availabe.

" Sample of a webcam stream from Tokyo "
Mjpeg exampleTokyo.
" Webcam from Vienna "
Mjpeg exampleVienna.

Performance of this simple implementation is quite good. The Tokyo example used the stream available at http://218.219.210.174:86/mjpg/video.mjpg?camera=1. Playing this stream with Pharo has no impact on CPU usage whereas playing the same stream with Chrome has a noticeable effect on CPU usage.