beets/beetsplug/bpd/gstplayer.py

# This file is part of beets.
# Copyright 2016, Adrian Sampson.
#
# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish,
# distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so, subject to
# the following conditions:
#
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.

"""A wrapper for the GStreamer Python bindings that exposes a simple
music player.
"""

import _thread
import copy
import os
import sys
import time
import urllib

import gi

from beets import ui

gi.require_version("Gst", "1.0")
from gi.repository import GLib, Gst  # noqa: E402

Gst.init(None)


class QueryError(Exception):
    pass


class GstPlayer:
    """A music player abstracting GStreamer's Playbin element.

    Create a player object, then call run() to start a thread with a
    runloop. Then call play_file to play music. Use player.playing
    to check whether music is currently playing.

    A basic play queue is also implemented (just a Python list,
    player.queue, whose last element is next to play). To use it,
    just call enqueue() and then play(). When a track finishes and
    another is available on the queue, it is played automatically.
    """

    def __init__(self, finished_callback=None):
        """Initialize a player.

        If a finished_callback is provided, it is called every time a
        track started with play_file finishes.

        Once the player has been created, call run() to begin the main
        runloop in a separate thread.
        """

        # Set up the Gstreamer player. From the pygst tutorial:
        # https://pygstdocs.berlios.de/pygst-tutorial/playbin.html (gone)
        # https://brettviren.github.io/pygst-tutorial-org/pygst-tutorial.html
        ####
        # Updated to GStreamer 1.0 with:
        # https://wiki.ubuntu.com/Novacut/GStreamer1.0
        self.player = Gst.ElementFactory.make("playbin", "player")

        if self.player is None:
            raise ui.UserError("Could not create playbin")

        fakesink = Gst.ElementFactory.make("fakesink", "fakesink")

        if fakesink is None:
            raise ui.UserError("Could not create fakesink")

        self.player.set_property("video-sink", fakesink)
        bus = self.player.get_bus()
        bus.add_signal_watch()
        bus.connect("message", self._handle_message)

        # Set up our own stuff.
        self.playing = False
        self.finished_callback = finished_callback
        self.cached_time = None
        self._volume = 1.0

    def _get_state(self):
        """Returns the current state flag of the playbin."""
        # gst's get_state function returns a 3-tuple; we just want the
        # status flag in position 1.
        return self.player.get_state(Gst.CLOCK_TIME_NONE)[1]

    def _handle_message(self, bus, message):
        """Callback for status updates from GStreamer."""
        if message.type == Gst.MessageType.EOS:
            # file finished playing
            self.player.set_state(Gst.State.NULL)
            self.playing = False
            self.cached_time = None
            if self.finished_callback:
                self.finished_callback()

        elif message.type == Gst.MessageType.ERROR:
            # error
            self.player.set_state(Gst.State.NULL)
            err, debug = message.parse_error()
            print(f"Error: {err}")
            self.playing = False

    def _set_volume(self, volume):
        """Set the volume level to a value in the range [0, 1.5]."""
        # And the volume for the playbin.
        self._volume = volume
        self.player.set_property("volume", volume)

    def _get_volume(self):
        """Get the volume as a float in the range [0, 1.5]."""
        return self._volume

    volume = property(_get_volume, _set_volume)

    def play_file(self, path):
        """Immediately begin playing the audio file at the given
        path.
        """
        self.player.set_state(Gst.State.NULL)
        if isinstance(path, str):
            path = path.encode("utf-8")
        uri = f"file://{urllib.parse.quote(path)}"
        self.player.set_property("uri", uri)
        self.player.set_state(Gst.State.PLAYING)
        self.playing = True

    def play(self):
        """If paused, resume playback."""
        if self._get_state() == Gst.State.PAUSED:
            self.player.set_state(Gst.State.PLAYING)
            self.playing = True

    def pause(self):
        """Pause playback."""
        self.player.set_state(Gst.State.PAUSED)

    def stop(self):
        """Halt playback."""
        self.player.set_state(Gst.State.NULL)
        self.playing = False
        self.cached_time = None

    def run(self):
        """Start a new thread for the player.

        Call this function before trying to play any music with
        play_file() or play().
        """

        # If we don't use the MainLoop, messages are never sent.

        def start():
            loop = GLib.MainLoop()
            loop.run()

        _thread.start_new_thread(start, ())

    def time(self):
        """Returns a tuple containing (position, length) where both
        values are integers in seconds. If no stream is available,
        returns (0, 0).
        """
        fmt = Gst.Format(Gst.Format.TIME)
        try:
            posq = self.player.query_position(fmt)
            if not posq[0]:
                raise QueryError("query_position failed")
            pos = posq[1] / (10**9)

            lengthq = self.player.query_duration(fmt)
            if not lengthq[0]:
                raise QueryError("query_duration failed")
            length = lengthq[1] / (10**9)

            self.cached_time = (pos, length)
            return (pos, length)

        except QueryError:
            # Stream not ready. For small gaps of time, for instance
            # after seeking, the time values are unavailable. For this
            # reason, we cache recent.
            if self.playing and self.cached_time:
                return self.cached_time
            else:
                return (0, 0)

    def seek(self, position):
        """Seeks to position (in seconds)."""
        cur_pos, cur_len = self.time()
        if position > cur_len:
            self.stop()
            return

        fmt = Gst.Format(Gst.Format.TIME)
        ns = position * 10**9  # convert to nanoseconds
        self.player.seek_simple(fmt, Gst.SeekFlags.FLUSH, ns)

        # save new cached time
        self.cached_time = (position, cur_len)

    def block(self):
        """Block until playing finishes."""
        while self.playing:
            time.sleep(1)

    def get_decoders(self):
        return get_decoders()


def get_decoders():
    """Get supported audio decoders from GStreamer.
    Returns a dict mapping decoder element names to the associated media types
    and file extensions.
    """
    # We only care about audio decoder elements.
    filt = (
        Gst.ELEMENT_FACTORY_TYPE_DEPAYLOADER
        | Gst.ELEMENT_FACTORY_TYPE_DEMUXER
        | Gst.ELEMENT_FACTORY_TYPE_PARSER
        | Gst.ELEMENT_FACTORY_TYPE_DECODER
        | Gst.ELEMENT_FACTORY_TYPE_MEDIA_AUDIO
    )

    decoders = {}
    mime_types = set()
    for f in Gst.ElementFactory.list_get_elements(filt, Gst.Rank.NONE):
        for pad in f.get_static_pad_templates():
            if pad.direction == Gst.PadDirection.SINK:
                caps = pad.static_caps.get()
                mimes = set()
                for i in range(caps.get_size()):
                    struct = caps.get_structure(i)
                    mime = struct.get_name()
                    if mime == "unknown/unknown":
                        continue
                    mimes.add(mime)
                    mime_types.add(mime)
                if mimes:
                    decoders[f.get_name()] = (mimes, set())

    # Check all the TypeFindFactory plugin features form the registry. If they
    # are associated with an audio media type that we found above, get the list
    # of corresponding file extensions.
    mime_extensions = {mime: set() for mime in mime_types}
    for feat in Gst.Registry.get().get_feature_list(Gst.TypeFindFactory):
        caps = feat.get_caps()
        if caps:
            for i in range(caps.get_size()):
                struct = caps.get_structure(i)
                mime = struct.get_name()
                if mime in mime_types:
                    mime_extensions[mime].update(feat.get_extensions())

    # Fill in the slot we left for file extensions.
    for name, (mimes, exts) in decoders.items():
        for mime in mimes:
            exts.update(mime_extensions[mime])

    return decoders


def play_simple(paths):
    """Play the files in paths in a straightforward way, without
    using the player's callback function.
    """
    p = GstPlayer()
    p.run()
    for path in paths:
        p.play_file(path)
        p.block()


def play_complicated(paths):
    """Play the files in the path one after the other by using the
    callback function to advance to the next song.
    """
    my_paths = copy.copy(paths)

    def next_song():
        my_paths.pop(0)
        p.play_file(my_paths[0])

    p = GstPlayer(next_song)
    p.run()
    p.play_file(my_paths[0])
    while my_paths:
        time.sleep(1)


if __name__ == "__main__":
    # A very simple command-line player. Just give it names of audio
    # files on the command line; these are all played in sequence.
    paths = [os.path.abspath(os.path.expanduser(p)) for p in sys.argv[1:]]
    # play_simple(paths)
    play_complicated(paths)