Audio skew
#1
I have a Pioneer Amp (SC-LX86) connected to my Pioneer TV (PDP-LX509) via HDMI.
I also have my PC (HP Z210) connected to the Amp via HDMI.
For the moment i only have some crappy L+C+R speakers connected to the Amp which i hope to resolve shortly Smile

The TV does minimal video processing or enhancements and is set to display 'dot for dot' so video processing delays should be minimized and overscan eliminated.

Unfortunately i am noticing a frustrating audio skew which luckily can be corrected within XBMC on a per movie basis (by adding an audio delayed of 150ms).
However the audio skew does not occur if i connect the PC directly to the TV via HDMI but in this instance XBMC must do the audio decoding as the TV only seems to handle stereo PCM!

I don't understand where the audio skew is coming from.
In fact i thought the later versions of HDMI were supposed to fix audio skew issues automatically Confused

Does anyone have any info on what may cause the audio skew issue when the Amp is in the loop and how to fix such a problem?

(edited to clarify type of audio skew)
(edited to clarify TV does minimal video processing/enhancement)
I'm a XBMC novice :)
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#2
Well audio lip-sync is definitely part of HDMI 1.3 specification.

And my TV is HDMI version 1.3 compliant (according to the manual) so it should support lip-sync.
But my Amp manual states nothing about the version of HDMI supported (thanks to the HDMI's consortium's hate of version numbers and like of optional features)....

Anyway there is a setting within the Amp Audio menu called A.DELAY that if set to ON will ensure the audio/video is syncronized (lip-sysn).
There's also a DELAY setting that allows delays to be added to pre HDMI 1.3 equipment and other analog inputs.
So now it's back to the Amp menu (which Pioneer designed in a more convoluted way than was needed) to play with the A.DELAY settings to see if that would help...

I'll report back within the next few days...
I'm a XBMC novice :)
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#3
It turns out that the A.DELAY setting within my Pioneer Amp was already set to ON so the Amp should play nice with the Pioneer TV and compensate for audio skew but unfortunately this setting seems to do nothing from what i can hear.

So i still have an ~150ms audio skew when playing a movie via XBMC but no audio delay when playing the same movie via VLC Confused
The only difference between the two players is that XBMC passes the audio stream direct to the amp while VLC processes it and passes stereo pcm.

I'm not keen to use the Amps DELAY setting and force a fixed 150ms delay (though it's actually defined in frames IIRC) on the HDMI port used by the PC, nor am i keen to simply set a per unit audio delay of 150ms within XBMC.

I'd really like to understand why i'm having this issue and where the audio skew is coming from. Does anyone have any ideas?
I'm a XBMC novice :)
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#4
(2014-02-12, 09:24)skylarking Wrote: It turns out that the A.DELAY setting within my Pioneer Amp was already set to ON so the Amp should play nice with the Pioneer TV and compensate for audio skew but unfortunately this setting seems to do nothing from what i can hear.
Have you try to turn off the delay in Pioneer Amp?
>Alienware X51- do it all HTPC
>Simplify XBMC configurations
>HOW-TO Bitstreaming using XBMC
I refused to watch movie without bitstreaming HD audio!
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#5
Try disabling audio passthrough in audio settings within Xbmc. It's the only work around that I've found for me with an Onkyo AVR and Samsung TV.
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#6
Why would you want to turn passthrough off ? The best way to solve this is just to set up the delay in xbmc for all videos, which takes only a second.
I hadn't responded yet because I am not sure why these delays occurs exactly, but disabling all the great passthrough stuff seems like a radical solution.

Quote:And my TV is HDMI version 1.3 compliant (according to the manual) so it should support lip-sync.
Nice, but of course the audio never gets to your TV when using the AMP.
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#7
(2014-02-12, 16:24)SkinnyT Wrote: Try disabling audio passthrough in audio settings within Xbmc. It's the only work around that I've found for me with an Onkyo AVR and Samsung TV.
I never have any issue with Delay using XBMC passthrough option on Onkyo AVR's with all type of HDTV's...
>Alienware X51- do it all HTPC
>Simplify XBMC configurations
>HOW-TO Bitstreaming using XBMC
I refused to watch movie without bitstreaming HD audio!
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#8
(2003-10-02, 13:10)Gamester17 Wrote: a such tool would be great, but i'm pretty sure that the official xbmc devs don't have time to make one

I didn't have a problem when I ran raspbmc on my Pi. I wonder if maybe I have an old home cable or something.
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#9
(2014-02-12, 16:15)bluray Wrote:
(2014-02-12, 09:24)skylarking Wrote: It turns out that the A.DELAY setting within my Pioneer Amp was already set to ON so the Amp should play nice with the Pioneer TV and compensate for audio skew but unfortunately this setting seems to do nothing from what i can hear.
Have you try to turn off the delay in Pioneer Amp?

Yes i have, in fact i've tried all the settings i can find within the Amp but i get the same result, approximately 150ms skew in most but not all movies...

(2014-02-12, 16:45)Kib Wrote: Why would you want to turn passthrough off ? The best way to solve this is just to set up the delay in xbmc for all videos, which takes only a second.
I hadn't responded yet because I am not sure why these delays occurs exactly, but disabling all the great passthrough stuff seems like a radical solution.

Quote:And my TV is HDMI version 1.3 compliant (according to the manual) so it should support lip-sync.
Nice, but of course the audio never gets to your TV when using the AMP.
Kib, i must confess i don't understand how lip-sync works but for lip-sync to be useful i would expect the video processing device would notify the audio processing device of the delay that the video engine requires, then the audio processing device can adjust accordingly. Great when both processing devices are carried out in the same box but when they are carried out in different boxes, some form of hdmi data transfer must occur to make this feature meaningful (for those that have a separate display device and audio device). But as i said, i don't understand how the basic hdmi 1.3 lip-sync works (let along how the more elaborate dynamic lip-sync available in hdmi 2.0). Lets hope lip-sync is not just marketing words (BS).

Also the audio skew problem was not evident on one or two movies i watched through the Amp. Unfortunately i didn't make a mental note of which movies were ok so now i have to find them again and look at the audio/video streams to see if there is anything that may hint at why this is not a universal issue for me. For now, a global 150ms delay is only a temporary solution that is ok for most of my BD rips.

(2014-02-12, 16:24)SkinnyT Wrote: Try disabling audio passthrough in audio settings within Xbmc. It's the only work around that I've found for me with an Onkyo AVR and Samsung TV.
I want the pure unadulterated audio stream sent by XBMC to my Amp in all it's glory so the Amp display can indicate what encoding scheme i'm listening too. So turning off passthrough is not a solution for me...

I would still like to understand where the audio skew is coming from so if anyone has any ideas on what more i can do to isolate the issue before the return window on my Amp expires (in a month) and before i spend a bucket load of money on new speakers, it would be greatly appreciated.

Thanks to all for their posts to date.
I'm a XBMC novice :)
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#10
Just dial in 150ms audio offset for all video and stop worrying about it. It's not your AMP.
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#11
Make sure deinterlacing is set to auto not always. I understood it could cause an extra delay when enabled for progressive video.
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