clapper: Add media caching via download to local storage

[Rafostar]

The aim here is to stream an online video/audio while also at the same time download/cache it to disk (excluding adaptive content).

After download is complete, further playback and seeking are done using the locally cached file. This functionality uses GStreamer "downloadbuffer" element.

Player will emit a signal with a local download location after it completes, so application can backup it if it wishes to reuse the same media file in future.

When player goes to stopped state (which also happens when media item changes) downloaded file is removed, so player will by itself cache one media at a time (without filling up the disk space).

[Rafostar]

Example code to test (this time in Python :smile:):

#!/usr/bin/env python3

import gi
gi.require_version('Adw', '1')
gi.require_version('Clapper', '0.0')
gi.require_version('ClapperGtk', '0.0')
gi.require_version('GLib', '2.0')
gi.require_version('Gtk', '4.0')
from gi.repository import Adw, Clapper, ClapperGtk, GLib, Gtk
import shutil

Clapper.init(None)

download_dir = GLib.build_filenamev([GLib.get_user_cache_dir(), "example_download_dir", None])
print('Using ceche directory: {0}'.format(download_dir))

def on_download_complete(player, item, location):
    # Media downloaded. Data from this file is still used for current playback (including seeking).
    print('Download complete: {0} => {1}'.format(item.props.uri, location))

def on_activate(app):
    win = Gtk.ApplicationWindow(application=app, default_width=640, default_height=396)
    video = ClapperGtk.Video()
    controls = ClapperGtk.SimpleControls(fullscreenable=False)

    # Enable local storage caching and monitor it
    video.props.player.set_download_dir(download_dir)
    video.props.player.set_download_enabled(True)
    video.props.player.connect('download-complete', on_download_complete)

    # Configure playback
    video.props.player.props.queue.set_progression_mode(Clapper.QueueProgressionMode.CAROUSEL)
    video.props.player.set_autoplay(True)

    # Create and add media for playback
    item_1 = Clapper.MediaItem(uri='http://commondatastorage.googleapis.com/gtv-videos-bucket/sample/BigBuckBunny.mp4')
    item_2 = Clapper.MediaItem(uri='http://commondatastorage.googleapis.com/gtv-videos-bucket/sample/ElephantsDream.mp4')
    video.props.player.props.queue.add_item(item_1)
    video.props.player.props.queue.add_item(item_2)

    # Assemble window
    video.add_fading_overlay(controls)
    win.set_child(video)
    win.present()

# Create a new application
app = Adw.Application(application_id='com.example.ClapperDownloadCache')
app.connect('activate', on_activate)

# Run the application
app.run(None)

# Finally app should cleanup before exit. Possibly moving data to
# another dir if it wants to use it on next run and deleting what's
# left (so any unfinished downloads will also be removed).
print('Cleanup')
shutil.rmtree(download_dir)

GST_PLUGIN_FEATURE_RANK=vah264dec:300 python3 ./test.py