5.1 DTS -> 5.1AC3 - only stereo
#1
Hi. I recently bought raspberry pi 2 and installed newest OpenELEC on it.
I have many movies with dts 5.1 sound, unfortunately my tv supports only Dolby Digital via hdmi.

Using my notebook, dts -> AC3 transcoding works flawlessy. On my pi I can only hear stereo sound.

I set number of channels to 2.0, activated decoding on external device, checked Dolby Digital (AC3) capable receiver and Enable Dolby Digital transcoding.

As I said it looks like audio is downmixed to 2.0.
However, on this settings I get full 5.1 on movies, that already have dolby digital audio.

I have pi 1 too, it has the same problem plus it usually can't keep up with audio.

What should I do?
Thanks
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#2
Can you try disabling omxplayer in video/acceleration settings.
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#3
It's perfect now, thanks Smile

So I suppose we have a bug in omxplayer?
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#4
(2015-02-14, 00:52)l0udpl Wrote: So I suppose we have a bug in omxplayer?

No. omxplayer runs the audio sink on the GPU. It has no ability to encode AC3 audio, so can't support transcode.
Possibly we should disable omxplayer automatically when audio transcode is enabled.
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#5
Please, can you tell me your audio configuration?
I'm not able to get passthrough, only get noise.

Which brand is your tv? Here http://forum.kodi.tv/showthread.php?tid=...pid1935745 we are using sonys and can't get ac3 passthrough

Thanks
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#6
I'm using Philips tv (2013 or 2014 model) with some kind of old Panasonic home cinema system connected via optical link.

Previously I had Sony TV too (older model) and I was using dts passtrough on notebook with xbmc.
As I remember that Sony TV was kind of annoying, because I had to manually switch it to "external speakers" (or something like that) via menu triggered by "Options" button on remote. Otherwise it would downmix to stereo and after that pass it via optical link.
I'm afraid it's not going to help you as you're getting noise only. I may test new raspberry on that old TV, but it'll take around a week as I don't have access to it right now...
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#7
Thank you.

You're right, I have to manually switch to external speakers in tv, otherwise it downmixes.
I can get passthrough with omxplayer, problem is with dvdplayer. I want to do the same as you, ac3 transcoding because tv doesn´t pass dts signal to receiver.
If you don´t mind, it would be helpful to know if you can do ac3 passthrogh in your Sony tv.

Regards
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#8
Looks like being a problem with Kodi dvdplayer in combination with Sony.

I've been struggling with the problem of getting only static noise when playing AC3 sound from dvdplayer with passthrough enabled. For a test I have now tried temporarily moving the HDMI connection to a a Philips tv and this seems to work ok.

It looks like it's not a Pi-related problem as others have reported the exact same problem on other platforms: http://forum.kodi.tv/showthread.php?tid=214114
Interestingly enough someone in the thread mentions that the problem does not exist with an older Kodi version.
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#9
I've tried the version he says, xbmc 13.2 with openelec 4.2.1 and it doesn't work. His device is an Ouya.
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#10
I couldn't tell from the posts whether you were using a receiver and speakers or just the tv. In my system all signal producing devices (Bluray, WDMP. Pi etc go to the receiver first through HDMI and a single HDMI feeding the TV input (Toshiba) . The TV is only used for a picture, all sound is handled by the receiver. No problems with any kind of decoding
HWF
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#11
Kind of repeating what Harpanet13 says, but I have all Sony equipment (TV, PS3 as BluRay player, and DTS Home Theater receiver). I found that if you put the TV in the middle (playback device --> TV - Audio Out via HDMI --> Home Theater Receiver), it down mixes the signal, even with HDMI passthrough enabled. The only way I could get 7.1 sound on my blue-rays was by direct connecting the device to the Home Theater (device --> Home Theater - Video out via HDMI --> TV). This setup can be a pain, because you have to use two remotes when you want to switch the source device, but it was the only way I could get full theater audio.
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#12
I think that with tv in the middle you can only get ac3 passthrough, and you need to tell the tv to use external speakers, because if not it downmixes to stereo.
You can run tvservice -a in a raspberry to see the tv supported codecs
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#13
Thanks guys, I came across the same issue. Disabled omxplayer and everything is great now Smile

So, as suggested above, it should be disabled by default when transcoding is activated. Better yet, it could be disabled "on the fly" on a case by case basis. This way omxplayer would still be used whenever transcoding is not required.

Cheers
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#14
(2015-03-03, 00:18)joshcube Wrote: Kind of repeating what Harpanet13 says, but I have all Sony equipment (TV, PS3 as BluRay player, and DTS Home Theater receiver). I found that if you put the TV in the middle (playback device --> TV - Audio Out via HDMI --> Home Theater Receiver), it down mixes the signal, even with HDMI passthrough enabled. The only way I could get 7.1 sound on my blue-rays was by direct connecting the device to the Home Theater (device --> Home Theater - Video out via HDMI --> TV). This setup can be a pain, because you have to use two remotes when you want to switch the source device, but it was the only way I could get full theater audio.

If you are routing your audio via your TV then you are likely to either be using Toslink/Coax or ARC (Audio Return Channel) over HDMI (where audio is sent 'the wrong way' back to an amp from a display via a limited bandwidth secondary audio connection). Both of these are limited to PCM 2.0 or DD/DTS legacy compressed. ISTR that DD and DTS codecs only support a max of 5.1 audio, with DTS EX carrying either discrete or matrixed 6.1 channel audio.

For 7.1 audio you will need HDMI carrying either 7.1 HDMI multichannel PCM or HD Audio bitstreamed. The Pi only supports HDMI multichannel.
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#15
(2015-05-14, 12:25)marvalar Wrote: Thanks guys, I came across the same issue. Disabled omxplayer and everything is great now Smile

So, as suggested above, it should be disabled by default when transcoding is activated. Better yet, it could be disabled "on the fly" on a case by case basis. This way omxplayer would still be used whenever transcoding is not required.

It's a valid suggestion. I'll look into it.
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