HDMI audio

All being well, I should soon be getting an HDMI switch that also provides digital output (de-embedding) via spdif. The device itself is said to work with sample rates up to 192k, but I’ve not used or tested such a device before, so I have one basic question wrt this.

Do such switches require the monitor/screen/output device to also support a given audio sample rate before they will accept them and de-embed to spdif?

I ask because my current monitor (and the one on my wife’s machine) only list up to 48k/24 LPCM when checked. So I’m wondering if I’d need a better monitor before the HDMI switch would accept the audio, and hence won’t provide a > 48k output unless the monitor will accept it.

Ultimately it’s the EDID which decides what audio formats the computer will use, so either the monitor needs to have native support for the format or the switch needs to rewrite the EDID in order to signal support for more formats. So it will all come down to whether the switch is “just” a switch or whether it contains some extra logic as well.

Um. That raises the obvious question: How does the prospective buyer tell how a specific switch will behave without buying and taking a gamble? What specs I’ve seen make no mention of this.

FWIW The one I’m likely to get is the Monoprice HDX-401TA. But as with others, I’ve not seen this question covered.

A few seconds in Google (ie. just searching for the model number) shows that folks on avsforum are failing to get 5.1 audio out of that unit unless the monitor supports it. Therefore I’d suggest that it is a waste of money for your purposes :( Also, it is crazy expensive (100$, so about 75ukp). You can find units from about 15ukp that offer the ability to run in different modes (eg. pass through, override EDID etc)… but we’ve had that discussion already.

As of latest ROOL changes, the display manager can accept “dropped on” EDID. This opens the possibility of using saved EDID info from a “known good” device, I guess. I haven’t been able to test that yet, though.

Just to be clear, I would be very wary of paying that much for a unit, unless you are very clear on what it can do for you. Others are pulling SPDIF out for much less. However, the issue with all of these will be >48khz, since most sources tend not to know about SPDIF>48khz.

The one I’m buying is second-hand for much less money than the amounts you quote. I’m buying it mainly for tests. I know that it can do >48k, but as we’ve discussed, it may mean the monitor or downstream HDMI device also has to accept it.

Again, as I’ve discussed elsewhere already.

A) If someone knows of a unit that de-embeds up to 192k/24 LPCM stereo even when used with an HDMI destination device that doesn’t accept >48k and I can buy from a UK address via cheque-in-post. Please let me know.

B) I’ve said I probably want a new monitor anyway for display reasons. And I’d wish for one that can accept 192k.

More generally, given that RO systems can now output high rez via HDMI we really do need to have users informed about what devices can support what. At the moment we have no clear idea what anyone should buy if they want 192k stereo. It isn’t enough that RO can output it. To use it we’d need a suitable output device. And most ‘soundbars’ and monitors aren’t likely to cope well.

Given that no-one has provided info to let me choose an appropriate device I’m doing what seems I need to do. To get some examples and do some tests. That can help me tell others what to avoid or prefer, depending on their individual requirements.

So if you know of a device that does de-embed 192k LPCM and lets me buy as I wish, please let me have the details and I’ll get one. Indeed, I’m quite prepared to buy more than one type/model to compare and be able to tell people about to save them having to do their own blind searches.

TBH Andrew I think it would make sense if you and CJE did stock/offer one or two such models as there will be people who would prefer to buy them from you rather than some shop/vendor who doesn’t support RO. Just offerring examples you knew and could say would de-embed without requiring monitor support would help RO users.

If people are going to hang the ‘way to get high quality digital audio’ hat on the peg ‘HDMI’ more than on ‘USB’ the above does need to become a better informed situation I fear. It isn’t enough to simply ensure that the RO box can send the info. People need more info to make full use of it. So I’m just doing what I can to illuminate this area.

The “HDMI Converter” (shudder) I’ve got, has three settings.
The first is passthrough.
This setting means that whatever the monitor gives you will get – this is the one I have to use as I want 1980×1200 display.
Unless you get a convertor that supports beyond HD resolution if you want high res displays then passthrough is your only option.

The second and third are 2Ch and 5.1 which are fairly obvious.
These modes replace the EDMI with a “standard” set that support 2Ch and 5.1 depending on which mode is selected.
However my “converter” only supports up to 1080p so I’m stuck with passthrough :-(

I’m really happy with 48k via SPDIF.

I think the main problem with supporting 192k is that the people who need it are likely to be very fussy.
i.e. I’d be pretty angry if I spent 200 quid on a high end convertor that didn’t work.
Buying say 5 of them to do a comparision for RISC OS users, I would guess isn’t practical for a return from a commercial perspective.

That said I’m interested in getting something nicer than the “converter” that I have.

My ideal would be around 50 quid, that supports 192k, SPDIF and 4K video.
I suspect it’s going to be hard to find anything for less than 150 quid, due to the market size of people wanting this kind of equipment.
But I hope to be wrong!

I’ve ordered another HDMI convertor that supposedly supports “4k”. It looks from the specs to be higher quality than my current one.
Assuming I’m feeling 100% and got over this nasty bug, which seems likely – I’m doing a talk at the WROCC this Wednesday where I’ll cover what I’ve discovered so far.

One thing that I’ve noticed, is that whether I’ve got above 48k support is pointless at the moment – all my audio mp3’s are 48k.
I should really do something about that!
PlayIt seems to only output at 44100

PlayIt seems to only output at 44100

You should be able to change the system rate and have PlayIt follow the rate you set.

One generic problem for HDMI monitors and other AV kit, though, is that they may insist on resampling everything into 48k. So some devices may accept other rates, but grind them all into 48k.

The above doesn’t matter for over-air broadcasts, iplayer files, or DVDs. May not matter for 48k/24 BD. But for CD-based material it can mean that if you play it the result gets forced into being 48k even when sending 44k, etc, via HDMI. Real PITA.

The root problem here is the obsessions and lazyness of the general AV biz. They lock down what happens and make assumptions about what mere users will do, or should be allowed to do. Since most people have no idea what is going on, they don’t complain.

The second and third are 2Ch and 5.1 which are fairly obvious.
These modes replace the EDMI with a “standard” set that support 2Ch and 5.1 depending on which mode is selected

Does the “2Ch” then allow and de-embed > 48k? If so, even when the monitor doesn’t accept > 48k? Or does it simple adopt the standard limitations common for TVs and monitors?

I realise that the market for >48k LPCM is small. But then that’s true for RO anyway. :-) But if HDMI is going to be seen and used as a ‘quality’ way to get audio out of RO in a digital form it does really need to offer users a way to get > 48k. I’m sure this is possible. The problem is identifying which specific bits of kit will do it and people might be best advised to choose.

My monitor only supports 48k, however…
According to sound check it does support 192000 when I turn on 2ch:

The bit I’m interested in is supporting >1080p and these modes, then it’s “nice” ;-)

That’s good news, I suspect. :-)

What model is it, and where did you buy it?

Do you have any way of testing its spdif output to ensure it doesn’t blindly downsample everything?

I think I’ve got a mp3 that is encoded at 19200.
If I use the 2Ch it seems to be the only one that plays.
The other mp3 are silent.
That said I can’t tell the difference!
Need to do some more digging I think

Couple of comments:

You may find testing easier with wave file. However mp3 should work, depending on what you’re using to play them. Unusual to have 192k mp3’s!

You may find ‘sox’ is useful as it will let you generate versions of a file with other sample rates so you can have the same nominal content for comparison purposes.

LOL…. the link is on the previous thread.
I won’t say where I bought it ;-)
I don’t have any ideas of how to test, techically or not whether it is blindly downsampling everything or not.

For the luser (i.e. me) I suspect any HDMI convertor that supports “pass-through” and SPDIF will do the trick. Don’t quote me on that!

As for how good/bad it is – I wish I had the time and knowledge.

I suspect if you want something decent, research is required.
But the main requirements would be 4K monitor support and 2Ch 192000 sound selection that doesn’t do anything “dodgy” – not sure what that could be.
If it is HDMI→SPDIF surely it’s more work to do something dodgy.
I know on my Playstation and Amazon Firestick, you have to select the correct sound frequency and options for the sound system you are connecting to. Otherwise you get diddly squat sound out.
That would make me assume (possibly wrongly) that there is usually no up or down sampling ever done with sound, that it is a “dumb” protocol.
i.e. if you send a 48k soundtrack down a 192k sound it ends up silent (which is what I’m seeing).
But that could be any number of other daft things I’m doing.

I’ll produce some documentation of what I’ve done so far for the write-up of my talk, so that will be in the newsletter – then be avaliable afterwards

I know this will make you sad, but the E-SDS one looks more promising.
Whether it is or not is another question, it should arrive tomorrow.
I should have enough time to look at it before the talk on Wednesday I hope.

My main issue is that I want something reasonable, my previous one is OK – but I’m not 100% happy – possibly 80% happy.
But I don’t need anything “high end” as I don’t have anything good enough to connect it to – I wish I did!

If it’s unusal to have mp3’s at 192k, then I guess it’s probably not – I know I’ve got a few higher than the normal rate when I did a custom conversion for some tracks.
I’ll do some custom mp3’s and flac etc. at 192k to see if I can get them to work and work out how to set the “system” rate to 192k as well.

Guess I should start being scientific about this rather than random!

Looks like 48k is the highest that I can play at through the soundbar.
Using DigitalCD seems to be the easiest way to prove it.
If I set the mixer speed to 48000Hz I get a sound, any higher I don’t get anything.
Everytime I change the setting I need to switch the sound bar on/off though.

I can’t tell any difference, but it makes me feel better. It sounds awesome anyway

I’ve verified this using !SoundCheck, so I’m guessing I get 192k to the soundbar – but it can’t handle it.
I could of course read the instruction manual, but there are strict rules against doing that.

Unusual to have 192k mp3’s!

Unusual? Unlikely! The normal upper limit for a legitimate MP3 is 48kHz, indeed that is all that my phone will accept (looking at the MTP properties information). Ditto AAC (though some can do 96kHz).

For 192kHz, you’ll probably be looking at FLAC…

You can set !DigitalCD to adopt whatever rate the file reports. It then will switch the rate as required when it plays each file. !SoundControl will list the available system rates.

You can also fix the rate and it should then convert. But that tends to introduce distortions so is best avoided unless you can employ a better rate convertor than the RO tendency to perform simple linear interpolations.

It would be weird to have an 192k sample rate mp3 because the ‘judgement rules’ would probably remove all the ultrasonic components anyway. So I’m wondering if you might have confused sample rate with bitrate.

I thought it was 192 – but don’t know about the bit rate or samplerate. Either way I was wrong.

I’ve got my new “Converter”, it seems to be better….according to !SoundCheck. This is in plain pass-through mode:
SoundCheck V1.22 – 28th Jan 2016
=========

• System settings *
  -————————

Number of rates available = 7

Current rate index = 3 => rate 48000 samples per sec

List of available system rates:

Rate index 1 => rate 32000 samples per sec
Rate index 2 => rate 44100 samples per sec
Rate index 3 => rate 48000 samples per sec
Rate index 4 => rate 88200 samples per sec
Rate index 5 => rate 96000 samples per sec
Rate index 6 => rate 176400 samples per sec
Rate index 7 => rate 192000 samples per sec

Sound system supports 16-bit audio.
DAC clock is slaved to external clock
Oversampling ON

The next set of values are the defaults for 8-bit VoiceGenerators
-———————————————————————————————
Number of VoiceGenerator channels = 1
Nominal sample buffer length = 960
Nominal sample buffer period = 21 [microsec]
VoiceGenerator Channel Handler pointer = 4211032128
Schedule Pointer = 537332564
-———————————————————————————————

Sound ON
Speaker ON

Volume setting = 127
Nominal Volume gain scaling x 1.000 [ 0.00dB ]

Tuning offset = 548.0469 [% of Octave]

• Now see if the system supports multiple devices *
  -——————————————————————

DMA able to handle multiple devices OK. :-)

Currently selected device:

ID string for the current device = SoundDMA#HAL_0007_16000000
Name of device = i.MX6 HDMI audio controller

Enumerate all available devices:

ID string for audio device = SoundDMA#HAL_0007_16000000
Name of device = i.MX6 HDMI audio controller

ID string for audio device = SoundDMA#HAL_0005_41000000
Name of device = SGTL5000-compatible audio controller

• Probe HDMI Audio *
  -——————-

• SoundControl settings *
  -———————————

required size for results = -16
set size to 16 ⁴ = 1 devices
If this is zero we are OK! = 0

adj stereo on [ 0] System gain = 0.00 Min -40.00 Max 0.00 Step 0.06 [dB]

• SharedSound settings *
  -——————————-

Handler number = 1
Handler 1
Flags = 1 Type = 0 Immediate

*

When using the “4K 2ch Audio” setting, the sound still worked fine – but as I assume because my monitor doesn’t do above 1920×1200 it was clipped at 1920 × 1080 and it showed far fewer modes. So I’m guessing the modes stored in the EDID are standard “Movie” modes.
So it looks like the pass through on this model is much better.
This one also specifies the default as “Copy HDMI out EDID” and it specifies:
“This HDMI to HDMI+audio converter converts the HDMI video signal to displayer/projector, and coverts the stripped HDMI audio signal via the digital Optical/ Coaxial\3.5mm audio output to amplifer or speaker, So that audio and video can be separated. the resolution of this converter can be up to 4096×2160/30Hz”

So I’m guessing it has completely replaced the HDMI audio section of the EDID as my monitor only has a 3.5mm jack.
There is no way it could ever do 7 Channel DTS!

Hi Malcolm!

Just for clarity, can you confirm the following:

1) In “Passthrough” mode, your monitor is able to do 1920×1200 (not a normal “TV” HDMI resolution), and picture is correctly displayed (no colour distortion or other corruption).

2) In “Passthrough” mode, audio EDID is re-written, showing up to 192khz in SoundCheck

[This is unexpected, as passthrough would normally pass audio settings too]

3) When set to 2ch/5.1ch override, it limits display to 720p/1080p/4k resolutions (no 1920×1200).
Does it offer a 1080p/2channel mode?

I think you’ve kinda already answered these, but it’d be helpful to have confirmation on the points, as it sounds like you’ve hit upon a pretty-much perfect solution.

I’d be interested to know what device it is. And does it accept and de-embed >48k when set to “2ch” mode even when the monitor can’t accept > 48k.

The key question for me is how anyone would de-embed to spdif >48k LPCM stereo when their monitor can’t accept it. Until people know which models can do this, and which can’t, chooing a de-embed device is a nightmare. Even simply knowing of one or two models that do it would be a big help.

The “E-SDS”https://www.amazon.co.uk/gp/product/B01DNNYL64/ model I linked earlier is the one I’m talking about now.
To answer Andrew’s questions.
1) Yes – in “pass-through” mode it shows ALL of the EDID modes that the monitor does (up to 1920×1200).
2) Yes – in “pass-through” mode the audio EDID is rewritten, showing up to 192khz in Soundcheck

I don’t think in this model it is passthrough for audio, just for the screen resolutions.

3) in 2Ch/5.1ch override it cuts the resolutions right down to only about 5 (for me) as I don’t have a 4K monitor.
So it looks like because my monitor doesn’t support 4k it only shows 1080p/2 channel in 2Ch mode.
I assume if I had a 4k monitor this would show the 4k modes through.

Just to add some information, both models I tried showed the monitor name when using “pass-through” and some other custom name when using 2/5.1Ch modes.
If you change the modes, I found it was better to power-cycle the unit and turn HDMI sound off and on again to ensure it was picked up fully.
The first one I used required the HDMI leads unplugging to, as these seemed to provide power for the unit.

The way this “converter” works seems to imply that it’s irrelevant what the monitor supports, which would make sense if you are stripping out the audio.

If someone buys me a 4k monitor, I’m more than willing to test it out for an extensive period…say 10 years?
The “converter” currently costs 26 quid, so it doesn’t break the bank.

It works for me™ and I’m happy with it – I’d be happier if I had a stonking sound system to connect it to.
But for that I’d need a nice detached house as well, again, I’m happy to soak test ;-)

On a slightly more realistic note, if people aren’t happy with that model, at least this should confirm what to actually look for and ask for.
As I’m not an enthusiast, as is clear by my above posts and am fudging my way through this.
At least I know there’s more to sound than on and off now!

Thanks Malcolm. In “Passthrough” mode, it sounds perfect – full audio capabilities, but with monitor-read screen modes.

I’ll get one ordered.

Jim, I’ll let you know how I fare.