Go to content Go to menu

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.

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

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: ''.
" 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 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.