dom
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Re: DTS-MA passthrough

Sat Jul 16, 2016 2:44 pm

flash_uk wrote:Have read the entire post and wanted to check if I understand the current position with RPi2 and RPi3...is it correct that:
- Hardware constraints mean that neither RPi2 or 3 will ever offer passthrough of TrueHD or DTS-HD MA
- Both Rpi2 and 3 CAN decode both TrueHD and DTS-HD MA, and output 8 channel PCM at 48kHz

So one additional question: how different in quality is audio output as 8 channel PCM at 48kHz versus audio output by an amp decoding say TrueHD or DTS-HD MA?
Your understanding is correct. The HD audio formats are lossless and the decoder should be bit exact, so there should be no difference in the audio with 8 channel PCM or passthrough.

There are some extensions like ATMOS which your receiver may be able to do something with, but ffmpeg doesn't, but I believe they are mostly for systems with > 8 speakers.

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MeneerJansen
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Re: DTS-MA passthrough

Wed Aug 10, 2016 9:14 pm

dom wrote:
ktf wrote:I am considering getting a Raspberry PI 2 to use it as a media player (both movies, all audio formats) and audio with an external DAC. If the external DAC only requires USB2 drivers, it should be fine on Unix, since those are native

Regarding the audio, in the end , what is the expected behavior on movies ? I have a receiver that is capable of decoding all DTS formats, but I understand the PI is not able to passthrough the lossless formats. What does it do to them ? Convert to PCM or discard anything ? I bet there are more people like me who are a bit confused by this :) It would be lovely to have a list of formats supported with pass through and a list of unsupported ones and the result of playing the latter
The HD audio passthrough issue is only related to HDMI output.
It depends where the content comes from. Blu-Ray mandates that non-HD audio is present. DTS-HD contains a 5.1 channel DTS core which can be passed through by the Pi (through HDMI).
Alternatively if the HD audio is TrueHD, then there must be a 5.1 channel AC3 track with the same content, which the Pi can pass through.

If passthrough is not available, then DTS or AC3 can be decoded by the Pi, and either output as 6 channel PCM (through HDMI), or downmixed to stereo (for analogue audio or HDMI if TV doesn't support multichannel PCM).

With the new libdcadec library, we can now decode 8 channel DTS-HD. TrueHD was already supported, and can produce 8 channel audio. These 8 channel formats can be output as 8 channel PCM, or downmixed.
Dear Dom,

Forgive me the following, stupid, question. Because I'm updating my knowledge about multi-channel audio. I'm from the time that DTS (what you'd call "DTS-core" now-a-days) and Dolby Digital 5.1 through an s/pdif digital output was state of the art. I have a Receiver w/ only s/pdif IN ports. No HDMI IN.

If I buy a new Recever/Amplifier that accepts HDMI-in, then can I playback DTS-MA and/or DD TrueHD w/ my Pi by letting my beloved Pi "decode" the DTS-MA or TrueHD audio strem to 8 (or less?) PCM channels? Will my amplifier then playback high fidelity audio over 5.1 speakers (I'm not going to buy more than 5.1 speakers!)?

And I take it that more than 2 PCM channels over s/pdif is impossible?

I realize that pass through of DTS-MA or TrueHD is technically impossible for the Pi. But that wouldn't be a problem to me if I can playback high def. audio via a PCM "workaround".

Regards,

Jansen
P.S. If I buy an external USB Blu-ray player (like the Asus SBC-06D2X-U (link)) can I play copy-protected encrypted Blu-ray's then w/ my beloved Pi? That is, can the BD's be decrypted?

dom
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Re: DTS-MA passthrough

Thu Aug 11, 2016 3:34 pm

MeneerJansen wrote: Forgive me the following, stupid, question. Because I'm updating my knowledge about multi-channel audio. I'm from the time that DTS (what you'd call "DTS-core" now-a-days) and Dolby Digital 5.1 through an s/pdif digital output was state of the art. I have a Receiver w/ only s/pdif IN ports. No HDMI IN.

If I buy a new Recever/Amplifier that accepts HDMI-in, then can I playback DTS-MA and/or DD TrueHD w/ my Pi by letting my beloved Pi "decode" the DTS-MA or TrueHD audio strem to 8 (or less?) PCM channels? Will my amplifier then playback high fidelity audio over 5.1 speakers (I'm not going to buy more than 5.1 speakers!)?
Yes, Pi can decode 8 channel DTS-MA/TrueHD losslessly and output it as 8 channel PCM. Your receiver will be able to downmix that to 5.1 (or you can let Kodi do the downmixing to 5.1).
And I take it that more than 2 PCM channels over s/pdif is impossible?
Yes. Two physical PCM channels is maximum over spdif. That can carry 5.1 channel compressed DTS or AC3.
P.S. If I buy an external USB Blu-ray player (like the Asus SBC-06D2X-U (link)) can I play copy-protected encrypted Blu-ray's then w/ my beloved Pi? That is, can the BD's be decrypted?
I believe Kodi has some ability to decrypt (libaacs) but I don't think it works for all titles.
I would recommend ripping the disks to ISO or mkv (without transcoding, which is lossless) and playing those from a network source.

dboy007
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Re: DTS-MA passthrough

Wed Sep 07, 2016 5:09 pm

What did you use for the HDMI input?

finite9
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Re: DTS-MA passthrough

Thu Feb 02, 2017 9:13 am

Hi Dom,

I've read this thread and the replies are frustratingly vague and disjointed.

First post you said it's not a hardware issue. Then later, you amended that to say it was a hardware issue because the (then) RPi 1 was not capable of physically handling 8 channels of 48KHz audio. Then people started asking about the RPi 2 and you said that that one could decode DTS-MA and convert it to PCM and output those 8 channels to a receiver if you had the Milhouse build. Other people have asked about DTS licensing and mentioned potential issues with the Broadcom firmware and it's ability to do passthrough. So now we've got the RPi 3 with the Broadcom Videocore IV chip which was not the same as used in the RPi 2, but from what i've read, your still saying that the hardware can't do it.

So the chain looks like this:

source material MKV with H.264 video/DTS-MA 8 channel audio stream
-->
RPi 3 HDMI 1.3 interface (ok for dts-ma passthrough interface wise)
-->
LibreELEC 7.95.1 using Kodi 17 RC3 (should have everything needed for DTS-MA and DD TrueHD: no longer a S/W issue)
-->
HDMI 1.3 cable to receiver
-->
Receiver capable of decoding DTS-MA and DD TrueHD

It cannot possible be a hardware issue as in "the hardware can't physically handle the stream data size" anymore.

It could be a licensing issue. If you have a license for DTS passthrough, you apparently need a license for DTS-MA passthrough as well. You have not answered this question at all, so we still do not know the status of this.

It could still be an issue of "the firmware in the Broadcom chip doesn't do it", which is another kind of hardware issue, but as the chip is significantly different in the RPi 3, we don't have any updated status from you guys on this front.

You've said that it will not happen because of hardware issues, even with RPi 3 and assumingly future releases, which implies that you know something along the lines of "Broadcom has told us they're not going to implement this, but we don't intend to go with another chip supplier and we don't intend to tell our users this".

The fact that RPi 2 can decode DTS-MA and send it out as PCM on 8 channels at the same bitrate implies that the hardware has been physically capable for some time, and that it's either a license issue or Broadcom implementation issue in the firmware and that you've hit a brick wall in getting either of those issues sorted out, but it would be appreciated if you just said so in that case.

I can DTS-ES passthrough to my Denon AVR-2310 receiver from RPi 3 and it works great. Annoying that I can't do the same for DTS-MA lossless or Dolby lossless. It's _not_ the same to decode it in the RPi and pass PCM stream to the receiver! There is a very clear difference in sound quality between PCM and DTS-MA decoding done in the receiver, that's got nothing to do with the specification of the signal being received... they both may be 8 channel 48/96KHz 24-bit, but when the receiver gets a DTS-MA signal it is able to implement it's channel levels and speaker distance measurements that are set up using e.g. Audyssey. This does not happen when it receives PCM signal, and then it's effectively in "pure" mode, so unless you have the perfect room setup, it's going to sound flat in comparison.

dom
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Re: DTS-MA passthrough

Thu Feb 02, 2017 1:08 pm

finite9 wrote: It cannot possible be a hardware issue as in "the hardware can't physically handle the stream data size" anymore.
It is a hardware issue. The Pi can output 8 channels of 48kHz PCM audio.
However trying to output 8 channels of 96kHz or 8 channels of 192kHz audio results in samples being dropped from the audio fifo.
This is purely a bytes/second limitation. We can for example output 2 channels of 192kHz PCM data.

Unfortunately the spec for HBR (high bitrate) passthrough, which is used by DTS-MA/TrueHD uses 8 channels of 192kHz audio.
It uses this whatever the actual sampling rate is.

Now 99% of BluRay content is 48kHz, so it seems perverse that to send the compressed audio stream requires a higher bandwidth than the uncompressed stream.
Most of the data transmitted is just zeros. But that is how it is. You cannot passthrough HBR audio using 8 channels of 48kHz samples.

However for the 48kHz content we can decode the audio losslessly (ffmpeg now supports both DTS-MA and TrueHD) and output the data as PCM.
Apart from out-of-band data like Dolby Atmos, this should produce identical output from your receiver as the passthrough data.
On a Pi2 or Pi3 the CPU usage required is insignificant (e.g ~10% of one core).

Remember VideoCore was designed for mobile phones a number of years ago so DTS-MA passthrough was not a priority.
The use case was never tested until we started getting requests on raspberry pi and only then was the limitation discovered.

finite9
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Re: DTS-MA passthrough

Fri Feb 03, 2017 9:37 am

Thanks for the clear answer! I'd misunderstood the 96KHz limitation...thought that dts-ma was 24/48.

Danielowenuk
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Re: DTS-MA passthrough

Fri Feb 17, 2017 2:11 pm

Clear answer; from a bitrate perspective I agree there would be no difference. But thats not the only benefit of having passthrough to a receiver.

When you decode to PCM you lose the metadata that can be used for things like dialog normalisation.

Not saying this should be a priority, nor am I saying I don't appreciate the detail you have gone into explaining what the Pi can do. Just want to be clear that it's not as simple as "PCM is just as good". And would be nice to think something could be done in a future version.

PlinyTheElder
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Re: DTS-MA passthrough

Tue Feb 21, 2017 3:40 pm

With the decoding it's been mentioned that it decodes to 8 channel 48KHz PCM, will this still be 24bit, or is it reduced to 16bit, forgive my ignorance, just can't seem to find any reference that confirms either way. Wasn't sure if the bandwidth is mostly frequency limited or if the bit depth also comes into play. Cheers!

dom
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Re: DTS-MA passthrough

Tue Feb 21, 2017 4:54 pm

PlinyTheElder wrote:With the decoding it's been mentioned that it decodes to 8 channel 48KHz PCM, will this still be 24bit, or is it reduced to 16bit, forgive my ignorance, just can't seem to find any reference that confirms either way. Wasn't sure if the bandwidth is mostly frequency limited or if the bit depth also comes into play. Cheers!
24-bit is supported. In fact the PCM data is always sent as 24-bit, so it just depends on what the source sends. Kodi supports 24-bit decode.

PlinyTheElder
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Re: DTS-MA passthrough

Wed Feb 22, 2017 12:43 pm

dom wrote:
PlinyTheElder wrote:With the decoding it's been mentioned that it decodes to 8 channel 48KHz PCM, will this still be 24bit, or is it reduced to 16bit, forgive my ignorance, just can't seem to find any reference that confirms either way. Wasn't sure if the bandwidth is mostly frequency limited or if the bit depth also comes into play. Cheers!
24-bit is supported. In fact the PCM data is always sent as 24-bit, so it just depends on what the source sends. Kodi supports 24-bit decode.
Thanks! That's really good to know. I'm trying to establish a device that will send 24Bit/48KHz PCM to a home cinema receiver and if I can prove no loss my Dad will believe me that the DTS light coming on will make no noticeable difference! Does that apply generally to pcm transfer in this fashion or specifically to the raspberry Pi? Many thanks Dom!

dom
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Re: DTS-MA passthrough

Wed Feb 22, 2017 3:02 pm

PlinyTheElder wrote:I'm trying to establish a device that will send 24Bit/48KHz PCM to a home cinema receiver and if I can prove no loss my Dad will believe me that the DTS light coming on will make no noticeable difference! Does that apply generally to pcm transfer in this fashion or specifically to the raspberry Pi? Many thanks Dom!
I believe the physical channel for hdmi audio alway uses 32-bit word with 24-bit audio (some signalling flags are in the other 8 bits).
It depends on the source device whether audio is truncated to 16-bit at any point between decode and render.
The Pi running Kodi should render 24-bit audio bit perfectly.

bootsmann
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Re: DTS-MA passthrough

Thu May 04, 2017 3:57 pm

Hi
I have a similar issue with a RPi 3 (Libreelec 8.0.1, Kodi 17.1):
I have activated passthrough and if I watch a movie with DTS my AVR shows me PCM instead DTS signal. But if I watch a movie with AC3/DD audio the AVR displays Dolby logo...
My old dreambox 800se passes through DTS signal correctly and AVR shows DTS logo on its display.

So, is this a RPi 3, Libreelec or a Kodi problem?

RPi with DD
Image
dreambox with DTS
Image
AVR <- dreambox <- dts signal
Image

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MeneerJansen
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Re: DTS-MA passthrough

Thu May 04, 2017 4:12 pm

bootsmann wrote:Hi
I have a similar issue with a RPi 3 (Libreelec 8.0.1, Kodi 17.1):
I have activated passthrough and if I watch a movie with DTS my AVR shows me PCM instead DTS signal. But if I watch a movie with AC3/DD audio the AVR displays Dolby logo...
My old dreambox 800se passes through DTS signal correctly and AVR shows DTS logo on its display.

So, is this a RPi 3, Libreelec or a Kodi problem?

RPi with DD
Image
dreambox with DTS
Image
AVR <- dreambox <- dts signal
Image
Make sure Kodi does not re-encode DTS to something else. Go to: System (settings) -> System -> Audio output -> deactivate "Dolby Digital transcoding" and enable "DTS capable receiver".

Hope this helps, it sometimes does... :-)

bootsmann
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Re: DTS-MA passthrough

Thu May 04, 2017 4:26 pm

Hi

I don't have this settings. Why?
Image

I see. I have to change to expert view..

Great it works!
thx

spooker
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Re: DTS-MA passthrough

Mon Aug 28, 2017 1:27 pm

Should we expect raspberry pi 4 to support dts MA and dolby true HD passthrough? If not I think that you should reconsider.

PatroSK
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Re: DTS-MA passthrough

Sun Sep 10, 2017 6:39 pm

Hello!
Is there any addon (to expansion board) for RPi3 with another HDMI output, capable to bitstream DTS-MA, Dolby TrueHD...?

euroecua
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Re: DTS-MA passthrough

Fri Mar 16, 2018 8:09 pm

Does anyone know if the new Raspberry Pi 3 Model B+ supports DTS MA and Dolby True HD passthrough?

AleXxX121
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Re: DTS-MA passthrough

Thu Sep 20, 2018 10:44 am

Hello, what is the better way to decode DTS-HD MA or Dolby TrueHD. I use a denon x4000 and a 4.1 setup. Should I adjust in kodi 4.1 or 7.1 and the whole mixdown let the reiver take over?
best regards

dom
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Re: DTS-MA passthrough

Fri Sep 21, 2018 12:09 pm

AleXxX121 wrote:
Thu Sep 20, 2018 10:44 am
Hello, what is the better way to decode DTS-HD MA or Dolby TrueHD. I use a denon x4000 and a 4.1 setup. Should I adjust in kodi 4.1 or 7.1 and the whole mixdown let the reiver take over?
It should work fine if you set "number of channels" to 7.1 (and denon will do the downmix from 7.1 to 4.1) or if you set number of channels to 4.1 (and kodi will do the downmixing).

Try both options and pick the one you prefer (they may sound identical).

lchiu7
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Re: DTS-MA passthrough

Tue Oct 23, 2018 7:04 pm

I am new to this forum but have been running a Pi for a while using Kodi and OpenElec. I recently upgraded to Atmos and tried playing some content to test it out, downloading some samples from Dolby's web site.

The Atmos logo appeared on the display of my Denon AVR-730H which was a nice surprise and it sounded great. So I tried some movies encoded in Atmos and the Atmos display didn't show up (I was playing directly with the media player in Kodi) and instead it showed DD+ Surround.

Doing more research I found this board where it clearly states the Pi3 (and other gens) cannot pass through TrueHD or DTS MA and I have my Pi set to passthrough. So it cannot play Atmos either. But clearly Atmos was playing on the demos I downloaded from Dolby. So I used Mediainfo to check them and they are actually DD+ with Atmos, not TrueHD with Atmos. So the lesser bandwidth of DD+ can be passed through and the height information from Atmos comes along fine.

But very few commercial videos are encoded as DD+ with Atmos so I might have to look at something like a Nvidia Shield instead if I want to backup my BD's and play them from the server with Atmos.

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