Sudden 'fuzzy' sound on raspberry pi 2 osmc rc2 after update

earlier this week (21st or 22nd April), after watching some videos from my Nas, I had a popup in osmc rc2 saying updates were available, so I accepted and installed them, and when it was done shutdown osmc and the pi from the osmc shutdown menu. I switched the power off at the wall as usual. the next day I started to watch a video and the sound was ‘fuzzy’, as if I’d blown my speakers, if you know that sound.

no source of video or music is clear sounding now. I’ve unplugged the audio from the audio jack on the pi (I don’t use hdmi sound output, but analogue to my stereo) and put it into my phone. the music I played was clear and crisp, so its not the stereo or the cable.

it happens if I switch to hdmi sound through the TV as well.

the coinciding update may be, well… coincidence, but it was working one day and not the next, with no other change except the update.

before I panic and buy a replacement pi board, could there be a software issue that can explain it?

I’ll entertain any ideas.

many thanks.

I would try a fresh install on a spare SD card before you go panicking about a hardware fault.

Try RC2 first - if you still have the same problem with the sound then try a fresh install of RC1. I suspect you’ll find it’s not related to RC1 vs RC2 (so far nobody else has reported this problem) but there could well be a configuration problem causing it.

thanks. I’ll try that. will take me a while to find the time to do it so I’ll post again with the result later this week.

turns out it was my stereo after all - it hums at high volume. the volume dial must have been bumped sometime between the update and my playing a video on OSMC. the reason it didn’t happen with my phone was that my phone audio output is much louder than OSMC on the Pi, so I had to turn the stereo volume down quite a bit in order to not blow my ears off. ditto for CDs.

so the problem now may be ‘why is the Pi audio output so low, even at 100%, that I have to crank up the volume on my stereo to achieve a decent volume’.

I’ll see if plugging it into a different rca audio-in port on the stereo makes any difference.

The analog output level on the Pi is quite a lot lower (about 6-10dB) than most other line level audio devices unfortunately, and it doesn’t have a wide dynamic range either. (It’s equivalent to about 11 or 12 bit audio)

The B+ and Pi 2 have a slightly higher output level than the original Pi but I think the difference is only 3dB so it’s not very noticable.

The only things you can really do are:

In Settings->System->Audio Output and make sure “Maintain original volume on downmix” is turned on (I think it’s on you want) - this will only have an effect when watching Dolby Digital/DTS surround tracks when they are being mixed down to 2 channels, it won’t affect a video that is already two channels.

If it’s mainly the dialog that is to quiet but other sounds are OK try increasing “Boost centre channel when downmixing” on the same page to between 3-10dB.

Finally if you press OK/Enter/Select during video playback to bring up the OSD controls, go into audio settings, you will see a setting Volume Amplification, increasing that will increase the volume of all channels whether the video is surround or stereo encoded and will also act as a limiter, reducing dynamic range. (Quiet scenes are made louder but loud scenes will not get any louder)

At the bottom of the dialog you can choose to make this new setting the default for all videos. (If you also watch music videos/concerts you will want to set those individually to 0 however as the limiter will not sound good on music)

I find 6 dB for volume amplification and 3dB for boost centre channel gives a pretty decent result on most videos, but keep in mind that the quality and volume of the analog output of the Pi is inherently somewhat limited.

thanks very much. I’ll play around with those settings and see what works best.

the morning i installed the update i got this exact issue.

it was a constant background hiss even with the volume on the machine at 0 but not tv at 0. i could slightly hear dialog still like a background feedback hissing echo in it.

everything sounded fine otherwise except for this hiss overriding everything it is awful and there even with music.

i also use the normal rca style jack as i dont have a hdmi tv.

it also showed up when i plugged my headphones into the jack to test. Im not sure if supposed to sound right that way in the first place though.

id also note my video/audio cable colors are all jumbled (video is red audio is yellow/white) but its always been like that since i just used some random cable i found.

this also may have occurred 2 times before when i first got my pi but i wrote it off because i didnt notice it again.

Do you have the normal master volume level in Kodi (adjusted with plus and minus keys) turned right up ? It doesn’t sound like you do…

With analog output from a Pi you should always have the master volume turned right up.

i just played with it and the hiss is still there.

i spent like 2 hours playing with settings that morning and the problem is still there.

the things always been a little odd with the fact the slider needs to be at around 50% or more to reasonably hear anything. but now with the hiss eh.

this hiss isnt nearly as noticeable with the volume up and things going on. its like there is this flawless sound then this horrible distortion trying to fill the empty space with it.

The analog output of the Pi has always had quite a bit of hiss, and dynamic range is quite limited so if you turn the master volume down too far it will get quite distorted. It’s always been like that I’m afraid, so I’m not sure why you haven’t noticed it before.

There was a bug in earlier versions of Kodi where the master volume did not actually work properly in omxplayer - you had to turn it down a long way to get much reduction in volume, because the volume values were calculated as a linear scale instead of logarithmic as it should be.

This means that now this bug is fixed a setting of 50% is MUCH quieter than it used to be, and now behaves the same as dvdplayer and Kodi on other platforms. However a setting of 100% should be exactly the same as before.

So my guess is you had your master volume set to less than 100% so you noticed the reduction in volume when that bug was fixed. As I suggested earlier in the thread, always use 100% for the master volume setting on analog output from a Pi. (Plus some volume amplification)

DBMandrake, the settings you suggested made a noticeable difference. thanks. but its only just good enough now, and considering the poor sound quality that the normal pi soundcard has I’m going to start another forum post asking for USB soundcard suggestions

one final update.

after some research i bought a soundblaster play usb soundcard (£17), since it appears on the Raspbian list of supported usb soundcards. with the pi turned off, i plugged it in, started the pi, used ssh to sudo apt-get update, and then sudo apt-get upgrade (because, why not?). then went to settings/system/audio and the new soundcard was there as an ALSA device.

I chose the ALSA analogue output, undid the settings you suggested above, DBMandrake, for the standard pi analogue audio and it just worked. the sound quality is noticeably better, and the volume is a bit higher too, allowing me to turn the stereo down more, further reducing any hiss.

money well spent, and the first time I’ve had a truly plug & play device for the pi that simply worked out of the box, with no config tweaking.


I had the same problem, resolved by the installation of PulseAudio (sudo apt-get install pulseaudio).