How to play 5.1 audio from a bluray player with sr-1000 or ims3000

[Miguel Moreno]

Greetings to all colleagues in film Tech.
I haave a very silly question.
How to get 5.1 trough HDMI bluray player in to a HDMI sr1000 or ims3000?

Recently i had a special event, a new movie that came on blu ray disc.
Its something we dont usually do so first i test with an original bluy ray movie that has 5.1 audio. The image looks great on screen but i found that my CP750 was sending only Left and Right audio ( Stereo).

I checked the audio output settings of the player and it was in PCM Multichannel but i dont know if i have to change something on the IMB´s in order to get the correct audio distribution like a DCP.

thanks for your help.

mike moreno

[James Gardiner]

I have not used that input for a while myself with a blueray,
But from memory, the IMS2000/3000 takes in the HDMI embedded audio and passes it out to the AES channels.
From memory it should support 5.1, encoded audio, likely ac3. and decode it in the IMS feeding 5.1 out the AES port. (Being a Dolby device I expect it comes with a license)
USL JSD60, I would pass the HDMI to the projector and coax or optical from the DVD player into the sound processor, but you needed to get the extra JSD60 option containing the Dolby decoder license for that to happen.

The issue with DVD/Blu Ray, you need something that can decode the audio into individual channels in the chain if you want more than 2-channel audio. And all multi-channel formats for domestic formats use licensed codecs, so it's problematic.

[Steve Guttag]

You shouldn't have to do anything. Verify that you've selected the correct version of audio track on your disc. Often, on USA pressings, other languages are stereo only (well, AC3 but if just PCM, it will just be 2-channel). If there are 5.1 PCM audio tracks on the disc, then you should get the PCM audio coming out of the respective IMBs. Note, the CP750 CAN do a Pro-Logic (and Pro-Logic II) decode, if you do have just two PCM channels so you can get back to 4.1 or 5.1 audio. The CP750 also has Coax and TosLink inputs that will decode AC3 tracks, if the player is set to bitstream on those outputs.

[Dave Macaulay]

BluRay is an audio nightmare.
All BluRay discs should have certain formats included as they are mandatory in the standard: linear PCM stereo, DTS digital 5.1, and Dolby digital 5.1. But they often don't - the standards are enforced just like the DCI standards - and then there are a bunch of optional extra formats like Dolby TruHD, ATMOS, and DTS-HD. New formats can be included, the optional list is open.
And as a bonus: a movie might have multiple disc versions... ie if you want Dolby TruHD or ATMOS you could need a particular version and these can be hard to find.
If you have a disc with AC3 and manage to program your player to default to that, you should get digital 5.1 sound from just about any IMB or internal server.
Most if not all linear PCM stereo tracks are compatible with ProLogic decoders but I have found one that isn't so the channels fade in and out like when decoding an FM music station.
The Dolby Digital AC3 5.1 patents fully expired in 2017 so it is apparently now license free, but the Doremi IMB decoded it before then (long before Dolby took over). I don't know if they were licensed or not, but none I know of have the Dolby logo indicating they are.

[Leo Enticknap]

As a general rule when passing BD player audio through the HDMI input of an IMB or IMS, I find that forcing the player's output to LPCM (i.e. no Dolby or DTS) does the trick.

[James Gardiner]

Note, If using Toslink (optical) or coax for audio from a DVD/BR player, it can only do 2 channels of uncompressed. OR a compressed multi channel format like ac3 or others. Of which a device down the chain needs to know how to split up into uncompressed channels and fed into the sound processor.

Embedded Audio on HDMI can do 8 channels. So a play MAY be able to convert to 5.1 and feed into the IMS uncompressed 6 channels of audio. This should be possible but I have never seen this functionality in a domestic player. But then again, I have not looked hard. But worth looking for the option.

[Thomas Piccione]

I cannot speak for the SR-1000, but on our IMS-3000, it passes through just about any HDMI embedded audio from our Oppo bluray player exactly as it is sent. If it's a 2.0 mix, it will output as 2.0 to the AES output. We've had no issues with bitstream formats like TrueHD and DTS. We also do not have any licenses with our IMS 3000, so this is a base level feature as far as I can tell.

[Leo Enticknap]

So a play MAY be able to convert to 5.1 and feed into the IMS uncompressed 6 channels of audio. This should be possible but I have never seen this functionality in a domestic player.

The higher end ones definitely can, e.g. both the 2K and 4K Oppos, and the Panasonic model we started to install after Oppo quit the disc player business (sorry: can't remember the model number). It wouldn't surprise me if a typical $70 player from Walmart can't, though.

[Harold Hallikainen]

It really seems like decoding (decompression) of the audio should happen in the player and then multichannel sound would be sent as PCM over HDMI. It further seems like the player should be able to poll the device to determine how many channels of PCM it supports, then send a mix with that number of channels. Does HDMI support polling of the receiving device and configuring audio based on that? If so, do cinema servers that support HDMI tell the source that they support 6 or 8 channel audio? This stuff should just work.

[James Gardiner]

@Harold, yes, in general, you can set priorities of codec to choose. But as you have competing codecs doing the same thing. There is no clear order of priority, and as such, generally, you need to set a priority by hand, or the preferred codec, that then selects a basic fallback, typically prefers -> ac3 -> stereo. But really, it's all a bit of a mess and there is no defined path like you would find in cinema land.

[Harold Hallikainen]

Is that preference set in the player, or in the device receiving the audio and video over HDMI. It SEEMS that the device receiving the audio should just be able to say, in order of preference, I'd like 7.1, 5.1, stereo and let the player figure out how to decode the disk and deliver. In cinema, it looks like we have decoders in the player, in the server receiving the HDMI, and in the sound processor receiving the audio over AES3. Since HDMI and multi-pair AES3 support 7.1, why ask for decoding at the far end?

[James Gardiner]

@harold, yes, you would typically see a good domestic sound processor have such configuration options, but also the player can have them too. Even TV/Large flat-screen units can have them. I have been meaning to turn my option on my TV to hard-coded if I can as the auto-detect takes a few seconds to kick in when changing channels, starting a stream, or pausing a stream. Annoying.

If you ask me, domestic audio options are a mess as competing licensed codecs tried to own the market , only making it confusing and clumsy. Most people have no idea whats going on.
Hell, I get confused with all the options. I do keep on top of it and I at least studied it as part of coding against it years ago.
At least HDMI can now do uncompress 8ch. and for me. I wish they would always just output uncompressed so we can forget about detecting codecs, and all the issues with initialising a codec etc. just a basic uncompressed bitstream please...

For example, the old dCine product, as toslink/coax could not do uncompressed 6ch, we ended up using a filter that could upmix/passthrough and real-time encode to ac3 at the highest bitrate possible (If not already ac3), so we could just send audio out 5.1 reliably over toslink/coax. No jumping from this to that.
And on computers at the time, that was the best way to get a digital audio signal into the audio chain, no analogue up until typically decoded in the sound processor. And use sound processors that could decode ac3.

[Leo Enticknap]

The two devices at either end of an HDMI connection are supposed to exchange EDID data with each other upon initial hookup, figure out what each other is capable off, and agree to send the highest possible quality of pix and audio from the source to the sink, based on what both can support. In practice this doesn't always work reliably. Audio, IMHO, is the most frequent cause of trouble. Even though Barco and GDC IMBs cannot handle anything other than LPCM embedded audio with HDMI for transcoding into AES3 and onward transmission to the audio processor, you will frequently hear silence if playing a Dolby or DTS-encoded disc, unless and until you go into the player's settings menu and forcing the HDMI audio output to LPCM, even if the player believes from the EDID handshake with the Alchemy or SX-3000 (for example) that it can send Dolby or DTS. In my experience, the player cannot usually figure out automatically that it can only send LPCM audio.

[Paul Finn]

I have seen conditions where the HDMI EDID source output will always default to the lowest number of channels it sees compatibility with in the devices in the chain. If there is a HDMI video monitor (TV) that can only handle two channel stereo in the chain for example, under HDMI rules, the player will only output two channel stereo in the HDMI stream regardless of how the player output is configured. I have seen this even with two HDMI output Oppo players.

As others have said, HDMI can be a jumbled puzzle to solve and different with every different combination of equipment. If multi channel (5.1/7.1) analog audio is available from the player, it is often better to use it if the cinema processor has the inputs, and keep the video and audio chains separate.

Paul Finn