Mpris Position is always zero

[shawnc722]

Querying the current position/time of a song always returns zero, for example:

$ dbus-send --print-reply=literal --dest=org.mpris.MediaPlayer2.ShairportSync /org/mpris/MediaPlayer2 org.freedesktop.DBus.Properties.Get string:'org.mpris.MediaPlayer2.Player' string:'Position'
   variant       int64 0 

Retrieving metadata works perfectly and the progress string is still accessible from dbus, so this seems to be specific to the Position method. I looked through the mpris related files to see if I could fix it myself, but most of it went over my head lol.

[mikebrady]

Thanks for the post. Yeah, unfortunately, the Position method isn't implemented. The reason for delaying implementing it is that it would have to be essentially interpolated. The progress string gives a snapshot of the play position (in frames) at a particular time, but it's not a particularly regular signal, and its arrival time (it comes from the player to Shairport Sync) is not necessarily a good indicator of when it was true. OTOH, there is probably nothing available that is more accurate at the moment.

So, Shairport Sync would have to record the time of arrival of the progress string and then interpolate from that to the time of the Position request to give an approximate position.

I'll put its implementation on the list!

[shawnc722]

I made a quick python script to monitor changes in the progress string, and it seems to be sent once near the beginning of a song and then not again unless I manually scrub through the song. To test the accuracy I made a little progress bar for a terminal and added the remaining time so it's as similar to the ios one as possible, and the dbus timing is indistinguishable from my phone's on my setup at least. I was expecting it to be off by maybe a couple seconds, so the precision was a pleasant surprise.

Here's the source code, if you or anyone else want to test it on a different setup:

#!/usr/bin/env python3
from subprocess import check_output
from time import sleep,time
lastcur = 0
t = -1
termwidth = 80
non_bar_chars = len('|| x:xx')
while True:
    cmd = "dbus-send --print-reply=literal --dest=org.gnome.ShairportSync /org/gnome/ShairportSync org.freedesktop.DBus.Properties.Get string:'org.gnome.ShairportSync.RemoteControl' string:'ProgressString'"
    progstr = check_output(cmd, shell=True).decode().split()[1]
    start, cur, end = [int(i) / 44100 for i in progstr.split('/')]
    cur, end = cur - start, end - start
    if cur != lastcur:
        t = time()
        lastcur = cur
    progress = round((termwidth - non_bar_chars) * (cur + time() - t) / end)
    to_end = end - (cur + time() - t)
    print('|' + '+' * progress + '-' * (termwidth-non_bar_chars-progress) +
          '| ' + f'{to_end // 60:0.0f}:{round(to_end % 60):02d}',end='\r')
    sleep(0.1)

Python's Idle doesn't support the \r command, so this has to be run in a terminal to work properly. Also, it seems very inefficient to query dbus at 10hz but since any shairport-sync implementation probably won't have to use dbus, the code to detect dbus flags doesn't seem relevant or worth writing.

I'll probably keep poking around at this whenever I have time, but I don't know enough about the shairport-sync internals or threading in c++ to be confident at making it myself. Thanks as always for all your work on this project!

[mikebrady]

Many thanks!

[github-actions]

This issue has been inactive for 60 days so will be closed 7 days from now. To prevent this, please remove the "stale" label or post a comment.

[ytzeng1]

Any plans to implement position in MPRIS interface? I would like to get time-synced lyrics using mpris lyrics app like Sunamu. Thank you very much!

[fritz-fritz]

Hey @mikebrady can we remove the stale label and reopen this? This is a feature that would certainly still be nice to have!

[mikebrady]

Greetings @shawnc722, @ytzeng1 , @fritz-fritz. Just FYI, this MPRIS Position property is working now, as are remote control commands to AirPlay 2 clients.