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Discussion Starter · #1 ·
I'm new here, first day!


I know this question is a bit peripheral to HTPC and more amp/receiver related, but I thought this would be best tested by a HTPC connected to an amp than anything else.


What happens if you guys feed your amp/receiver with a 7.1 audio track/stream via HDMI if you only have 5.1 or 4.0 speakers connected to the amp?


The reason why I ask is that I have been messing about with bitstream and PCM for various reasons and in sondoing I downdoaded a 7.1 channel check TrueHD m2ts clip. This cycles through each speaker in turn. When I bitstream the TrueHD track, the extra channels ( the two surround back in the case of the 5.1 setup and these and the center and sub channels in the 4.0 setup) are automatically matrixed to the available speakers and are heard (the rear surround go to the side surround and the center go to the fronts equally). Unfortunately if I set my PC to decode the TrueHD and send out a 7.1 PCM via HDMI my amp does not matrix the extra channels and I get silence for the missing speakers. Not a huge problem for 5.1 as there are very few movies out with surround rear channels ( I think LOTR has a 6.1 track), but in a 4.0 setup I would lose dialogue from the centre by sending PCM. More than just annoying!


If you have a full speaker complement, you can test this by temporarily turning off the center or rear surrounds in the amp menu to none. Or I you have a 5.1 setup turning the centre to none. Toggling between bitstream and PCM on the PC should make it obvious if you lose the center channel.


Can you post the make of your amp and the results please?


SBR
 

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Quote:
Originally Posted by Sandy B Ridge /forum/post/20823288


I'm new here, first day!


I know this question is a bit peripheral to HTPC and more amp/receiver related, but I thought this would be best tested by a HTPC connected to an amp than anything else.


What happens if you guys feed your amp/receiver with a 7.1 audio track/stream via HDMI if you only have 5.1 or 4.0 speakers connected to the amp?


The reason why I ask is that I have been messing about with bitstream and PCM for various reasons and in sondoing I downdoaded a 7.1 channel check TrueHD m2ts clip. This cycles through each speaker in turn. When I bitstream the TrueHD track, the extra channels ( the two surround back in the case of the 5.1 setup and these and the center and sub channels in the 4.0 setup) are automatically matrixed to the available speakers and are heard (the rear surround go to the side surround and the center go to the fronts equally). Unfortunately if I set my PC to decode the TrueHD and send out a 7.1 PCM via HDMI my amp does not matrix the extra channels and I get silence for the missing speakers. Not a huge problem for 5.1 as there are very few movies out with surround rear channels ( I think LOTR has a 6.1 track), but in a 4.0 setup I would lose dialogue from the centre by sending PCM. More than just annoying!


If you have a full speaker complement, you can test this by temporarily turning off the center or rear surrounds in the amp menu to none. Or I you have a 5.1 setup turning the centre to none. Toggling between bitstream and PCM on the PC should make it obvious if you lose the center channel.


Can you post the make of your amp and the results please?


SBR

I can't answer your question specifically but you should be sending an encoded signal(DTS/DD...etc)to the receiver whenever possible, PCM should be a second resort.
 

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4 channel speakers is usually no problem (in my case ONKYO 606). Use WASAPI exclusive mode for multichannel LPCM.


BTW why do you want to send multichannel LPCM instead of sending compressed audio bitstreams (except for those BDs with only LPCM audio tracks)?
 

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Discussion Starter · #4 ·

Quote:
Originally Posted by renethx /forum/post/20823468


4 channel speakers is usually no problem (in my case ONKYO 606). Use WASAPI exclusive mode for multichannel LPCM.


BTW why do you want to send multichannel LPCM instead of sending compressed audio bitstreams (except for those BDs with only LPCM audio tracks)?

Having much trouble with 23.976 as my amp has an unbypassable video processor that reclocks it to 24.00 giving annoying stutter every 40s or so. I also can't get anything close to 23.976 with the current iGPU 2500k. Trying to select any of the NTSC frequencies in windows just bombs out and gives [email protected] There's a thread on the intel forums about it with a promise that intel are looking into it!


That means having to 'reclock' the 23.976 bluray to 24.00 in the HTPC and therefore resaampling the audio to 24.00 which can't be done and keep bitstreaming. I'm using jRiver 'Video Clock' to do this rather than fiddle about with Reclock filter and it works fine (except that my amp ignores the chaannels for the missing speakers).


I am therefore between a rock and a hard place. The amp refuses to deal with 23.976 properly and stutters, but will deal with bitstreaming properly. Or I get smooth unstuttering video at 24.00, but missing channels due to having to send the audio as reclocked PCM.


SBR
 

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I see. For PCM, try WASAPI exclusive mode (JRMC supports it). If HD audio bitstreaming works with your AVR + 4.0 speakers, then PCM in WASAPI exclusive mode should work too. Windows speaker configuration is totally irrelevant in WASAPI exclusive mode as Windows audio engine will be bypassed.


Another workaround may be bypass AVR for video. Connect DVI port to your display directly (with a DVI-HDMI adapter), HDMI port to AVR for audio (+ another half of the desktop). Or HDMI to display and DVI to AVR (if your mb supports audio over DVI). There are a bunch of BD movies whose HD audio is LPCM, so you still have to use WASAPI exclusive mode.
 

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Discussion Starter · #7 ·

Quote:
Originally Posted by Calcvictim /forum/post/20823751


When you send the audio using PCM, do you change your speaker configuration in both windows and jriver to 4.0?

Well, sort of yes and no!


I am using WASAPI exclusive.


My original plan was to try and mess about with remixing the audio as little as possible, so just decoding the TrueHD and DTS MA to 7.1 PCM and just reclocking the 7.1 PCM to 24.00 without doing anything else. This was in the belief that the (more expensive) amp would do a better job of downmixing the 7.1 to 4.0 or 5.1 or whatever than the PC.


However, setting jRiver up with 4.0 or 5.1 and letting the program do the biz does work well. I think it's called JRSS or something like that. The downside is that for 2.0 audio it gets sent as 5.1 or 4.0 also, so I lose 'bitperfect' output.


Actually, the pseudo surround for 2.0 is probably something I can live with for now.


Splitting the HDMI is an option and sending one to the TV and one to the Amp. This would solve the 23.976 issue (as long as I could get intel to do it! Or get a dGPU). I wonder what would be the effect of this on the EDID? The TV would report 23.976 and xvRGB (another thing missing from the amp that the tv supports!), but only 2ch sound. I believe that EDID overrides do not work with intel iGPU? Would I still be able to bitstream TrueHD and DTSMA if the EDID only showed support for 2 ch audio in the sink?


Cheers


SBR
 

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The two displays (TV and AVR [with no display device connected]) are totally independent even if they are connected to the same GPU. TMDS signals to TV do not carry audio (well, they can carry stereo audio, that the EDID of your TV tells), while those to AVR can carry audio in whatever format your AVR supports.
 
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