Slowdown and Speedup a song that is being played

[phalgunlolur]

Hello,

This is a feature request.

I was wondering if it would be possible to slow down a song that's being played by a specific amount (50%, for example) or speed it up on the fly

[virtuald]

I think I played with this a few years ago. We would only be able to implement this in Exaile if gstreamer had a plugin that Exaile could leverage to do it for us, and IIRC there was one but it made the audio sound pretty terrible? It's possible the situation has changed since then.

Here's a gstreamer plugin that might do this. I'm not sure if this is the one I tried. https://gstreamer.freedesktop.org/data/doc/gstreamer/head/gst-plugins-good/html/gst-plugins-good-plugins-scaletempo.html

[phalgunlolur]

Do I directly install this plugin through Exaile's plugin options?

[virtuald]

Oh, sorry. Those details are for anyone who might want to implement the requested feature. You can't use gstreamer plugins directly without modifying Exaile's code.

[phalgunlolur]

Gotcha. I was reading that traktor is able to do this natively, but I haven't verified it

[virtuald]

Looking through my development directory, I noticed that my initial testing of the gstreamer plugin is still there... it's basically the same as the replaygain plugin:

from xl import providers, event, settings
from xl.player.gst.gst_utils import ElementBin

from gi.repository import Gst


NEEDED_ELEMS = ["scaletempo"]


def enable(exaile):
    for elem in NEEDED_ELEMS:
        if not Gst.ElementFactory.find(elem):
            raise ImportError("Needed gstreamer element %s missing." % elem)
    providers.register("gst_audio_filter", ScaleTempo)


def disable(exaile):
    providers.unregister("gst_audio_filter", ScaleTempo)


class ScaleTempo(ElementBin):
    """
    Handles replaygain volume adjustment and pre-amp.

    Placed at 30 in the pipeline, since most elements should do their
    processing after it.
    """

    index = 30
    name = "scaletempo"

    def __init__(self):
        ElementBin.__init__(self, name=self.name)
        self.audioconvert = Gst.ElementFactory.make("audioconvert", None)
        self.elements[40] = self.audioconvert
        self.tempo = Gst.ElementFactory.make("scaletempo", None)
        self.tempo.rate = 2
        self.elements[50] = self.tempo
        self.setup_elements()

There's still a lot of UI work that would need to be done for someone to actually use this (for example, it speeds up every song by 2x).