HD audio support only with OpenELEC test builds and PCM?
#1
Question 
Are OpenELEC test builds the only way to get HD audio working on RPi 2, or are there other (stable) releases or options (Xbian?)?

I understand that RPi 2 doesn't support DTS HD-MA and TrueHD bitstreaming due to hardware limitations. But it appears that some OpenELEC test builds decode HD audio streams and can send a 5.1 (and higher?) PCM signal via HDMI.

On that topic, how can I verify that it is indeed using the DTS HD-MA stream, rather than the DTS CORE stream which is included in the HD-MA signal? They can be hard to distinguish without being able to do a/b comparison with test discs. With bitstreaming it's easy as you can check you AVR lights. Does Kodi's stream info show what are the file contents, or what is actually being played, i.e. is it trustworthy?
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#2
(2015-05-05, 14:31)Eklar Wrote: Are OpenELEC test builds the only way to get HD audio working on RPi 2, or are there other (stable) releases or options (Xbian?)?

As far as OpenELEC is concerned, only test and recent nightly builds include DTS HD MA support. It might also be in OSMC, Xbian and Arch builds, although I'm not familiar with these distributions so others that are will need to confirm.

(2015-05-05, 14:31)Eklar Wrote: I understand that RPi 2 doesn't support DTS HD-MA and TrueHD bitstreaming due to hardware limitations. But it appears that some OpenELEC test builds decode HD audio streams and can send a 5.1 (and higher?) PCM signal via HDMI.

Yes, it can output 7.1 PCM via HDMI.

If you configure less than 7.1 channels in Kodi then the DTS HD-MA library will downmix the audio to whatever number of channels you have configured. If you configure Kodi with 7.1 channels, then your amp will take care of any downmixing should you have less than 7.1 speakers.

(2015-05-05, 14:31)Eklar Wrote: On that topic, how can I verify that it is indeed using the DTS HD-MA stream, rather than the DTS CORE stream which is included in the HD-MA signal?

Open the Codec OSD while playing back a video.

If the first line is showing "s32p (24 bit)" then you're decoding audio with the DTS HD MA library. If not, you're decoding only the "DTS core" with the older DTS decode library.
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#3
Excellent news, thank you for the info!

Glad to hear this is worked on, as HD audio support is quite rare on various media centers and players capable of connecting to a NAS.
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#4
I have a question about this. Some of my movies that have a DTS-HD MA audio track show this in the OSD:

Code:
D(Audio: dts (DTS-HD MA) ([134][0][0][0] / 0x0086), 48000 Hz, 5.1(side), s32p (24 bit))

While others show this:

Code:
D(Audio: dts (DTS-HD MA) ([134][0][0][0] / 0x0086), 48000 Hz, 5.1(side), s16p)

As you can see both are DTS-HD MA 5.1 tracks, but one seems to be decoded differently than the other. Am I still listening to the DTS-HD track in the second case or is that the DTS core track playing?
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#5
You might want to post the mediainfo for both files - the s32p/s16p value may vary with the "bit depth" of the audio stream. All of my 7.1 DTS HD samples show "s32p (24 bit)" and have 24 bit depth. I'm assuming s32p/s16p means signed-32 and 16 bit quantities (24 bit samples may be treated as 32-bit?)

But certainly, if the OSD codec shows "fltp" in the first line then you're decoding using the old DTS Core decoding library.
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#6
(2015-05-05, 14:55)Milhouse Wrote:
(2015-05-05, 14:31)Eklar Wrote: I understand that RPi 2 doesn't support DTS HD-MA and TrueHD bitstreaming due to hardware limitations. But it appears that some OpenELEC test builds decode HD audio streams and can send a 5.1 (and higher?) PCM signal via HDMI.

Yes, it can output 7.1 PCM via HDMI.

If you configure less than 7.1 channels in Kodi then the DTS HD-MA library will downmix the audio to whatever number of channels you have configured. If you configure Kodi with 7.1 channels, then your amp will take care of any downmixing should you have less than 7.1 speakers.

Do you have any sense of what does a better job at downmixing, AVR or KODI?

Regrading DTS-HD bitstreaming, is this a pure hardware limitation or are there any licensing issues also?
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#7
You are right, it's related to the bit depth as can be seen with MediaInfo. As far as I can tell, all DTS HD 7.1 tracks seem to have a bit depth of 24, but with 5.1 tracks some are 16 bit and some are 24 bit.

I haven't seen "fltp" yet when playing DTS HD tracks, so I suppose it's all OK Smile
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#8
(2015-05-05, 19:18)MrMagic Wrote: I have a question about this. Some of my movies that have a DTS-HD MA audio track show this in the OSD:

Code:
D(Audio: dts (DTS-HD MA) ([134][0][0][0] / 0x0086), 48000 Hz, 5.1(side), s32p (24 bit))

While others show this:

Code:
D(Audio: dts (DTS-HD MA) ([134][0][0][0] / 0x0086), 48000 Hz, 5.1(side), s16p)

As you can see both are DTS-HD MA 5.1 tracks, but one seems to be decoded differently than the other. Am I still listening to the DTS-HD track in the second case or is that the DTS core track playing?

Pretty sure that just means the first track was sourced from a 24 bit master, and the second from a 16 bit master. Most audio is mixed in the 24 bit domain these days, but lower budget or older productions may well be 16 bit.
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#9
(2015-05-05, 20:09)Lamm Wrote: Do you have any sense of what does a better job at downmixing, AVR or KODI?

That topic is a whole can of worms. But there shouldn't be any difference, except in some situations where RPi/Kodi messes up the decoding in software - which I guess is possible with beta builds.

PCM is essentially uncompressed DTS HD-MA or TrueHD (which use lossless compression), and thus should be identical. PCM is transferred digitally to the AVR so the DAC in the AVR does the final decoding, thus there shouldn't be any difference in audio quality due to noisy electronics in the RPi or cabling.

Bottom line is that the only difference is that bitstreaming makes your AVR DTS blinkenlights go, and I think we're all suckers for that Tongue

Quote:Regrading DTS-HD bitstreaming, is this a pure hardware limitation or are there any licensing issues also?

My understanding is that it is a hardware bandwidth limitation of RPi, but would be nice to hear from someone who has more than google research as source Smile
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#10
(2015-05-05, 22:44)Eklar Wrote: My understanding is that it is a hardware bandwidth limitation of RPi, but would be nice to hear from someone who has more than google research as source Smile

Pretty certain popcornmix confirmed this. The Pi/Pi2 only supports an HDMI audio bandwith for up to 4x192kHz streams, which isn't enough bandwidth to carry a max bitrate DTS HD-MA or Dolby True HD stream, which can carry 5.1 at 192kHz / 24 bit, and as they are lossless compression they can't guarantee to reduce the data rate at all times by a third. (Complex audio won't compress that much)
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#11
The Pi1/Pi2 HDMI supports 8 channels up to 96Khz (or 4 channels at 192kHz), any more than this and it will resample down.

However virtually all DTS HD MA tracks on BluRay are 96KHz or below, so this 192Khz limitation shouldn't be a problem for the vast majority of users.
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#12
(2015-05-06, 03:24)Milhouse Wrote: The Pi1/Pi2 HDMI supports 8 channels up to 96Khz (or 4 channels at 192kHz), any more than this and it will resample down.

However virtually all DTS HD MA tracks on BluRay are 96KHz or below, so this 192Khz limitation shouldn't be a problem for the vast majority of users.

I think I only have one 5.1 192kHz Blu-ray. Akira - which is Dolby True HD. 192kHz multichannel is very rare as it can take up more bandwidth than a decent quality video track, and very few movies are recorded or mastered in 192kHz (there are also strong reservations as to whether it actually makes things sound worse in some set-ups - as you can get all sorts of harmonic issues)...

(Uncompressed 5.1 192kHz 24 bit audio is around 28Mbs, Uncompressed 5.1 48Kz 16 bit is around 4.6Mbs... Lossless Dolby True HD or DTS-HD MA Compression will get these down a bit - but not massively. For comparison - many VIDEO tracks are around the 15Mbs, and broadcast H264 HDTV is around the 8-13Mbs range usually...)
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#13
(2015-05-06, 03:24)Milhouse Wrote: The Pi1/Pi2 HDMI supports 8 channels up to 96Khz (or 4 channels at 192kHz), any more than this and it will resample down.

However virtually all DTS HD MA tracks on BluRay are 96KHz or below, so this 192Khz limitation shouldn't be a problem for the vast majority of users.

So does this mean that in theory, the Pi1/Pi2 should be able to run DTS-HD bitstreaming (7.1ch 96KHz) if there was KODI/library code to support it?
If yes, is this something that might be coming to KODI down the line?
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#14
(2015-05-06, 14:17)Lamm Wrote: So does this mean that in theory, the Pi1/Pi2 should be able to run DTS-HD bitstreaming (7.1ch 96KHz) if there was KODI/library code to support it?
If yes, is this something that might be coming to KODI down the line?

No. The transport for DTS-HD (and TrueHD) uses 8 [email protected] even for 96kHz and 48kHz content.
I have tried outputting at 48/96kHz but the receiver doesn't detect it...
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#15
Not for the sake of your "green" AVR lamp ... and no we don't plan to change the way we are handling passthrough audio.
First decide what functions / features you expect from a system. Then decide for the hardware. Don't waste your money on crap.
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