Sound clipping issue after downmixing bugfix #96

strich opened this Issue Sep 21, 2012 · 12 comments


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strich commented Sep 21, 2012


We upgraded the firmware after the downmixing bugfix was applied to the firmware, which appears to have resolved it. Unfortunately there are now some sound quality problems in that the sound is 'clipping'.

Not sure what additional information I can give at this point.


popcornmix commented Sep 21, 2012

What are you running when you get this effect?
Is it clipping (i.e. distortion when loud signals are played, continuous through the track)
Or is it popping (occasional bursts of noise near the beginning and end of track, although can also occur on underruns).

Good work on getting us the elusive central channel. I can confirm the clipping. It's definitely clipping. While playing a .mkv with 6ch AAC audio with omxplayer or xbmc I get a substantial amount of it in louder scenes at any volume setting. I'm using analog as output.


popcornmix commented Sep 21, 2012

Do you have boost volume on downmix set in xbmc?

Boost volume on downmix is disabled.


popcornmix commented Sep 21, 2012

Analogue or HDMI audio?
Do you have an example file that exhibits the problem?

Seri- commented Sep 22, 2012

I can also confirm clipping with 7 Channel DTS Sound. Happens with HDMI audio (can't test analogue), boost volume is deactivated, sound output volume doesen't effect the clipping.

@torarin torarin referenced this issue in huceke/omxplayer Sep 22, 2012


Don't boost on downmix #55

Here is a sample that is not very good, I'll try to make a better one later.

Here is another sample. I'm using analogue output.

strich commented Sep 27, 2012

@torarin Should this issue be closed now as part of the fix in pull request 55 above?


popcornmix commented Sep 27, 2012

@strich Yes, this should be fixed. Have you tested it?

strich commented Sep 28, 2012

Tested it last night with a movie scene I know to have failed previously and it all looks good!
May want to wait for @evilpower to confirm as well before closing off.

Confirmed. Sounds much better. Even if your volume setting is a bit too high, clamping works like a charm. Good work!

@popcornmix popcornmix closed this Oct 28, 2012

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