[pypy-commit] extradoc extradoc: blog post draft about the realtime video processing

antocuni noreply at buildbot.pypy.org
Wed Jul 6 18:02:14 CEST 2011

Author: Antonio Cuni <anto.cuni at gmail.com>
Branch: extradoc
Changeset: r3823:bcd81510c9f9
Date: 2011-07-06 18:10 +0200

Log:	blog post draft about the realtime video processing

diff --git a/blog/draft/realtime_image_processing.rst b/blog/draft/realtime_image_processing.rst
new file mode 100644
--- /dev/null
+++ b/blog/draft/realtime_image_processing.rst
@@ -0,0 +1,51 @@
+Realtime image processing in Python
+Image processing is notoriusly a CPU intensive task.  To do it in realtime,
+you need to implement your algorithm in a fast language, hence trying to do it
+in Python is foolish: Python is clearly not fast enough for this task. Is it?
+.. image:: sobel.png
+Actually, it turns out that the PyPy JIT compiler produces code which is fast
+enough to do realtime video processing using two simple algorithms implemented
+by H&#229;kan Ard&#246;.
+XXX: add a very brief description of the algorithms
+You can try by yourself by downloading the appropriate demo:
+  - `pypy-image-demo.tar.bz2`_: this archive contains only the source code,
+    use this is you have PyPy already installed
+  - `pypy-image-demo-full.tar.bz2`_: this archive contains both the source
+    code and prebuilt PyPy binaries for linux 32 and 64 bits
+.. `pypy-image-demo.tar.bz2`: http://wyvern.cs.uni-duesseldorf.de/~antocuni/pypy-image-demo.tar.bz2
+.. `pypy-image-demo-full.tar.bz2`: http://wyvern.cs.uni-duesseldorf.de/~antocuni/pypy-image-demo-full.tar.bz2
+To run the demo, you need to have ``mplayer`` installed on your system.  The
+demo has been tested only on linux, it might (or not) work also on other
+  $ pypy pypy-image-demo/sobel.py
+  $ pypy pypy-image-demo/magnify.py
+By default, the two demos uses an example AVI file.  To have more fun, you can
+use your webcam by passing the appropriate mplayer parameters to the scripts,
+  $ pypy demo/sobel.py tv://
+To have a feeling on how much PyPy is faster than CPython, try to run the demo
+with the latter.  On my machine, PyPy runs ``sobel.py`` at ~47.23 fps on
+average, while CPython runs it at ~0.08 fps, meaning that PyPy is **590 times
+faster**.  On ``magnify.py`` the difference is much less evident, ~26.92 fps
+vs ~1.78 fps, and the speedup is "only" 15x.
+It must be noted that this is an extreme example of what PyPy can do.  In
+particular, you cannot expect (yet :-)) PyPy to be fast enough to run an
+arbitrary video processing algorithm in real time, but the demo still proves
+that PyPy has the potential to get there.
diff --git a/talk/ep2011/talk/demo.png b/blog/draft/sobel.png
copy from talk/ep2011/talk/demo.png
copy to blog/draft/sobel.png

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