[#4850] Preview for multimedia files

Currently, there is no preview for multimedia files,
such as video or audio files.

This changes implements the audio_preview, with simple
HTML5 <audio> tag

ckanext/audioview/plugin.py

@@ -0,0 +1,41 @@
+# encoding: utf-8
+
+from six import text_type
+import ckan.plugins as p
+
+ignore_empty = p.toolkit.get_validator('ignore_empty')
+
+DEFAULT_AUDIO_FORMATS = 'wav ogg mp3'
+
+
+class AudioView(p.SingletonPlugin):
+    '''This plugin makes views of audio resources, using an <audio> tag'''
+
+    p.implements(p.IConfigurer, inherit=True)
+    p.implements(p.IResourceView, inherit=True)
+
+    def update_config(self, config):
+        p.toolkit.add_template_directory(config, 'theme/templates')
+        self.formats = config.get(
+            'ckan.preview.audio_formats',
+            DEFAULT_AUDIO_FORMATS).split()
+
+    def info(self):
+        return {'name': 'audio_view',
+                'title': p.toolkit._('Audio'),
+                'icon': 'file-audio-o',
+                'schema': {'audio_url': [ignore_empty, text_type]},
+                'iframed': False,
+                'always_available': True,
+                'default_title': p.toolkit._('Audio'),
+                }
+
+    def can_view(self, data_dict):
+        return (data_dict['resource'].get('format', '').lower()
+                in self.formats)
+
+    def view_template(self, context, data_dict):
+        return 'audio_view.html'
+
+    def form_template(self, context, data_dict):
+        return 'audio_form.html'

ckanext/audioview/theme/templates/audio_form.html

@@ -0,0 +1,3 @@
+{% import 'macros/form.html' as form %}
+
+{{ form.input('audio_url', id='field-audio_url', label=_('Audio url'), placeholder=_('eg. http://example.com/audio.mp3  (if blank uses resource url)'), value=data.audio_url, error=errors.audio_url, classes=['control-full', 'control-large']) }}

ckanext/audioview/theme/templates/audio_view.html

@@ -0,0 +1,9 @@
+{% set res_url = resource_view.get('audio_url') or resource.get('url') %}
+
+<audio style="margin:auto; max-height:100%; display:block; min-width: 100%;"
+controls src="{{ resource_view.audio_url or resource.get('url') }}">
+  {% trans %}
+    Your browser does not support the <code>audio</code> element.
+    But don't worry, you can <a href="{{ res_url }}" alt="video url">download it</a>.
+  {% endtrans %}
+</audio>