Implement Video and Audio widgets

[martinRenou]

Implement a Video widget, at first I wanted to synchronize the progress of the video between views, but it turned out that it's quite difficult to do it. There is a timeupdate event on HTML video elements, but it's not triggered often enough to synchronize the views.

Edit: Also implement an Audio widget. Image, Video and Audio widgets have a common base class _Media

[martinRenou]

@maartenbreddels

[SylvainCorlay]

Lgtm. For the tests to pass you will need to update the spec file as per the test error message.

[martinRenou]

I also plan to make an Audio widget and it might be better to implement a base class named Media for widgets like Image, Video and Audio. The code will be quite the same for those three widgets.

[SylvainCorlay]

This looks good to merge.

Leaving it open for a bit so that jason or other people can comment.

[maartenbreddels]

Looking good!
I guess the Image unittests covers basically everything?
The only open issue I have is that a video can have multiple urls, for instance, if it does not support webm, it can take a mp4 file. Should we support this?

[SylvainCorlay]

Using multiple source tags would require providing different data for each case. That would completely modify the model to be a lot more complex (like a dict: format: data)... Not sure that it would be good for usability.

[martinRenou]

Also @maartenbreddels we may want to implement something like Video.from_download("bla.mp4") ?

[SylvainCorlay]

After the in-person discussion with @maartenbreddels and @martinRenou we decided to not add the possibility to have extra sources for the video widgets.

I think that eventually, we will add a sources attribute to media in ipywidgets 8, that will apply to

• video
• audio
• and picture, which should maybe underlie the Image widget?

[maartenbreddels]

For Python2 and 3 I use this:

try:
    from urllib import urlopen  # py2
except ImportError:
    from urllib.request import urlopen  # py3
value = urlopen(url).read()

Except that Python2 doesn't give an exception on a 404, and will happily feed you the 404 page. For Python 3 you get a proper exception. For the convenience of this, I suggest we add a from_download method.

[SylvainCorlay]

We discussed further on the means to download the media

• to the kernel
• to the client

and APIs.

This should probably be another PR.

Merging as per agreement with @jasongrout and @maartenbreddels.