Bug 401895 – media-libs/phonon-vlc media-libs/phonon-gstreamer : Initial crackling when listening to a sound event

• Product: Gentoo Linux
• Status: RESOLVED NEEDINFO

[Description Eric F. GARIOUD 2012-02-02 10:38:12 UTC]

When using either the gstreamer or the vlc backend, any sound event is preceded by a short but powerful crackling.

a/ This never occurs when using the xine backend
b/ There is no initial crackling when listening a multimedia file with dragonplayer even with either the gstreamer or the vlc backend.

c/ Using whatever x86_64 kernel from at least 2.6.38 to 3.2.1 included
d/ Using KDE 4.7.4 but this was also the case under last 4.6 stable
e/ Using media-libs/phonon-4.5.1-r1 + media-libs/phonon-gstreamer-4.5.0 + media-libs/phonon-vlc-0.4.0 + media-libs/phonon-xine-4.4.4

f/ No use of PulseAudio. The backend outputs to Alsa Default which is a pseudo device essentially made around dmix resampling_best to 44.100

g/ The audio device is an ICE1712 compatible device outputting through its analog outputs to an external audio amplifier.  

Reproducible: Always




I justify the reporting of this bug as well as its severity by the fact phonon-xine was removed from portage's tree.

[Comment 1 Johannes Huber (RETIRED) 2012-02-02 10:53:24 UTC]

Please file a upstream bug.

[Comment 2 Jorge Manuel B. S. Vicetto (RETIRED) 2012-02-02 13:27:43 UTC]

I've been using phonon-vlc since we added it to the tree and even though I've felt some "distortion" and "time lag" effects in the early stages, it currently works very well. I don't recall ever having the type of problem you describe.
I use phonon-vlc on a variety of boxes, including several desktops and laptops and output the sound to headphones, desktop speakers and through HDMI to my AV receiver.

[Comment 3 Eric F. GARIOUD 2012-02-04 13:43:01 UTC]

After investigating a little more, I think the problem is the lack of resampling.
Because :

- KDE sound events are 48Khz but my device is set up to 44.1 Khz
- If I play the file with any player without any specific resampling, I can hear the sound with the same crackling as the one reported when "played" through phonon-vlc | phonon-gstreamer.

The problem could be in fact linked to https://bugs.gentoo.org/show_bug.cgi?id=402151 I just reported.
Because as I implemented (and successfully tested with several players) resampling to 44.1 Khz as part of my Alsa_Default pseudo-device, if KDE sound events are not resampled when selecting the Alsa_Default device it would just mean that Alsa_Default is not the device actually used by phonon-vlc.

[Comment 4 Johannes Huber (RETIRED) 2012-03-16 14:43:17 UTC]

(In reply to comment #1)
> Please file a upstream bug.

We cant much do about it. So please file a bug upstream.

[Comment 5 Eric F. GARIOUD 2012-09-21 16:26:43 UTC]

(In reply to comment #3)
Since it is now possible to direct phonon-vlc's output to whatever resampling capable pseudo device, thanks to Bug 402151 resolution, this bug no longer concerns phonon-vlc. 

This would confirm that this crackling problem is actually a resampling problem.

The bug remains with phonon-gstreamer in its 4.6.2-r1 version.