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Plotting speed and error when calling update() using TkAgg

Hjalmar Turesson
Hi all,


I made a little video player using matplotlib. I need it to allow very good control over the playback speed (e.g. direction, frame-by-frame stepping and fast and slow).

However, it's not very fast. Max frame rate I can achieve is 10-20 fps.
I followed Basti's advice on speeding up plotting (http://bastibe.de/2013-05-30-speeding-up-matplotlib.html).
This resulted in a more than 2x improvement (from <5 to 10-20 fps), but I would like to reach 40-50 fps.

The core code is something like this:

self.im.set_data(self.video_frame)
self.text.set_text('some text')
     self.ax.draw_artist(self.im)
     self.ax.draw_artist(self.text)            
     self.im.figure.canvas.update()
     self.im.figure.canvas.flush_events()

video_frame is a 200 x 250 array. I tried lowering dpi from 100 to 50, but the improvement is marginal.

I saw that Harden (http://www.swharden.com/wp/2013-04-15-fixing-slow-matplotlib-in-pythonxy/) recommended using TkAgg over Qt4Agg since TkAgg is supposed to be faster.
But, TkAgg doesn't play nicely with figure.canvas.update(). I get the following error:
AttributeError: 'FigureCanvasTkAgg' object has no attribute 'update'
It works with Qt4Agg though.

Does anyone have a fix for this? Or some general advice on how to speed up playback speed?

I tried with both matplotlib 1.5.1 and the current version from github 2.0.0b4+2373.gb34c55d

Best regards,
Hjalmar

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Re: Plotting speed and error when calling update() using TkAgg

tcaswell
Instead of `canvas.update` call `self.im.figure.canvas.draw_idle()`.

IIRC `update` is part of the API inherited from Qt, not part of the API we ensure that all of the canvas objects have.

Tom

On Fri, Oct 7, 2016 at 4:48 PM Hjalmar Turesson <[hidden email]> wrote:
Hi all,


I made a little video player using matplotlib. I need it to allow very good control over the playback speed (e.g. direction, frame-by-frame stepping and fast and slow).

However, it's not very fast. Max frame rate I can achieve is 10-20 fps.
I followed Basti's advice on speeding up plotting (http://bastibe.de/2013-05-30-speeding-up-matplotlib.html).
This resulted in a more than 2x improvement (from <5 to 10-20 fps), but I would like to reach 40-50 fps.

The core code is something like this:

self.im.set_data(self.video_frame)
self.text.set_text('some text')
     self.ax.draw_artist(self.im)
     self.ax.draw_artist(self.text)            
     self.im.figure.canvas.update()
     self.im.figure.canvas.flush_events()

video_frame is a 200 x 250 array. I tried lowering dpi from 100 to 50, but the improvement is marginal.

I saw that Harden (http://www.swharden.com/wp/2013-04-15-fixing-slow-matplotlib-in-pythonxy/) recommended using TkAgg over Qt4Agg since TkAgg is supposed to be faster.
But, TkAgg doesn't play nicely with figure.canvas.update(). I get the following error:
AttributeError: 'FigureCanvasTkAgg' object has no attribute 'update'
It works with Qt4Agg though.

Does anyone have a fix for this? Or some general advice on how to speed up playback speed?

I tried with both matplotlib 1.5.1 and the current version from github 2.0.0b4+2373.gb34c55d

Best regards,
Hjalmar
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Re: Plotting speed and error when calling update() using TkAgg

Hjalmar Turesson
That works fine. And it explains why update() only worked with the Qt backends (I tried all). The speed is still not super impressive though (~20 fps), but I think I will just start skipping frames when playing at above 20 fps.

Thanks,
Hjalmar

On Fri, Oct 14, 2016 at 10:37 AM, Thomas Caswell <[hidden email]> wrote:
Instead of `canvas.update` call `self.im.figure.canvas.draw_idle()`.

IIRC `update` is part of the API inherited from Qt, not part of the API we ensure that all of the canvas objects have.

Tom

On Fri, Oct 7, 2016 at 4:48 PM Hjalmar Turesson <[hidden email]> wrote:
Hi all,


I made a little video player using matplotlib. I need it to allow very good control over the playback speed (e.g. direction, frame-by-frame stepping and fast and slow).

However, it's not very fast. Max frame rate I can achieve is 10-20 fps.
I followed Basti's advice on speeding up plotting (http://bastibe.de/2013-05-30-speeding-up-matplotlib.html).
This resulted in a more than 2x improvement (from <5 to 10-20 fps), but I would like to reach 40-50 fps.

The core code is something like this:

self.im.set_data(self.video_frame)
self.text.set_text('some text')
     self.ax.draw_artist(self.im)
     self.ax.draw_artist(self.text)            
     self.im.figure.canvas.update()
     self.im.figure.canvas.flush_events()

video_frame is a 200 x 250 array. I tried lowering dpi from 100 to 50, but the improvement is marginal.

I saw that Harden (http://www.swharden.com/wp/2013-04-15-fixing-slow-matplotlib-in-pythonxy/) recommended using TkAgg over Qt4Agg since TkAgg is supposed to be faster.
But, TkAgg doesn't play nicely with figure.canvas.update(). I get the following error:
AttributeError: 'FigureCanvasTkAgg' object has no attribute 'update'
It works with Qt4Agg though.

Does anyone have a fix for this? Or some general advice on how to speed up playback speed?

I tried with both matplotlib 1.5.1 and the current version from github 2.0.0b4+2373.gb34c55d

Best regards,
Hjalmar
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Re: Plotting speed and error when calling update() using TkAgg

tcaswell
To push much past 20Hz you will want to look into blitting.  See http://matplotlib.org/devdocs/api/animation_api.html for a rough introduction on how to use blitting (and see the animation code for an example of handling all of the corner cases).

Tom

On Fri, Oct 14, 2016 at 5:29 PM Hjalmar Turesson <[hidden email]> wrote:
That works fine. And it explains why update() only worked with the Qt backends (I tried all). The speed is still not super impressive though (~20 fps), but I think I will just start skipping frames when playing at above 20 fps.

Thanks,
Hjalmar

On Fri, Oct 14, 2016 at 10:37 AM, Thomas Caswell <[hidden email]> wrote:
Instead of `canvas.update` call `self.im.figure.canvas.draw_idle()`.

IIRC `update` is part of the API inherited from Qt, not part of the API we ensure that all of the canvas objects have.

Tom

On Fri, Oct 7, 2016 at 4:48 PM Hjalmar Turesson <[hidden email]> wrote:
Hi all,


I made a little video player using matplotlib. I need it to allow very good control over the playback speed (e.g. direction, frame-by-frame stepping and fast and slow).

However, it's not very fast. Max frame rate I can achieve is 10-20 fps.
I followed Basti's advice on speeding up plotting (http://bastibe.de/2013-05-30-speeding-up-matplotlib.html).
This resulted in a more than 2x improvement (from <5 to 10-20 fps), but I would like to reach 40-50 fps.

The core code is something like this:

self.im.set_data(self.video_frame)
self.text.set_text('some text')
     self.ax.draw_artist(self.im)
     self.ax.draw_artist(self.text)            
     self.im.figure.canvas.update()
     self.im.figure.canvas.flush_events()

video_frame is a 200 x 250 array. I tried lowering dpi from 100 to 50, but the improvement is marginal.

I saw that Harden (http://www.swharden.com/wp/2013-04-15-fixing-slow-matplotlib-in-pythonxy/) recommended using TkAgg over Qt4Agg since TkAgg is supposed to be faster.
But, TkAgg doesn't play nicely with figure.canvas.update(). I get the following error:
AttributeError: 'FigureCanvasTkAgg' object has no attribute 'update'
It works with Qt4Agg though.

Does anyone have a fix for this? Or some general advice on how to speed up playback speed?

I tried with both matplotlib 1.5.1 and the current version from github 2.0.0b4+2373.gb34c55d

Best regards,
Hjalmar
------------------------------------------------------------------------------
Check out the vibrant tech community on one of the world's most
engaging tech sites, SlashDot.org! http://sdm.link/slashdot_______________________________________________
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