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Original question:

PCM2704: Does the PCM270x support Windows10 ?

PCM2704: Is there a way to use PCM2704 SPDIF output for 5.1 configuration under Windows 10?

A R76
Prodigy 60 points
Part Number: PCM2704
Other Parts Discussed in Thread: PCM5122

Windows insists there are only 2 channels, which may be true as a DAC, but I'd like to interface to a receiver, via its SPDIF interface.

Since Windows only views 2 channels, I'm unable to passthrough via USB.

Ideas?

Thanks.

  • 0
    TI__Guru 53633 points
    Hi,

    I will check this in the lab tomorrow to see if I can achieve a 5.1 output.

    Thanks,
    Paul
  • 0
    Prodigy 50 points

    I also want to know this. The only playback device I can choose for the PCM2704 is "Speakers (USB AUDIO DAC)" but I can't get any of the software I use for media playback to do multi channel passthrough, which they can with a different DAC with SPDIF out.

  • 0 in reply to Johan Tenbrink
    Prodigy 60 points
    Wonder if there are registry entries that controls this; It appears Windows 10 insists on reformatting audio stream according to what the device tells it. Earlier Windows versions were not so protective..
    No wonder there are so many Android-based streaming boxes.
  • 0 in reply to A R76
    Prodigy 50 points
    I connected the 2704 to a Windows 7 VM (VMWare) bypassing the host OS but same problem. I can only choose "Speakers USB Audio Device".
    Yeah I've tried using both an RPi and an Android box as HTPC's but neither fits my needs 100%, only a Windows based HTPC will.
  • 0 in reply to Johan Tenbrink
    TI__Guru 53633 points

    Hi Johan and AR76,

    I believe Windows 10 allows the 5.1 configuration to be set by specific applications.  I have successfully configured my EVM to output 5.1 to my AV receiver using VLC.

    Below is the configuration I used:

    Windows sound settings:

    VLC Settings:

    I hope this helps!

    Thanks,

    Paul

  • 0 in reply to Paul_Frost
    Prodigy 50 points

    Hi Paul and thanks!

    Unfortunately I can't get it to work with these settings, should it be any difference whether toslink or coaxial is used? And what type of 5.1 sound did you use? I'm mostly interested in getting DTS 5.1 and Dolby Digital 5.1 to work and neither does.

  • 0 in reply to Johan Tenbrink
    TI__Guru 53633 points

    Hi Johan,

    I used the LFE and SBR test .wav file as shared on this page:

    https://www2.iis.fraunhofer.de/AAC/multichannel.html

    I would check that your AVR is also configured correctly to accept the 5.1.

    One thing I did not consider is if my AVR that I tested on was switching to Dolby Logic Pro Surround - so I will check this configuration again tonight.

    Thanks,

    Paul

  • 0 in reply to Paul_Frost
    Prodigy 60 points

    Thanks for your efforts, Paul. So far, we're in stereo world.

  • 0 in reply to A R76
    TI__Guru 53633 points
    Hi Everyone,

    I confirmed that I was operating with Dolby Logic Pro, so I was not able to achieve 5.1 surround. From my new understanding of the device, it cannot support DTS or Dolby Digital surround formats. I believe the device is only capable of 2.0 S/PDIF.

    I cannot find any example of this working with the PCM270x family in a product either.

    I think you are stuck with that, but I will say that Dolby Logic Pro does a pretty good job converting 2.0 to 5.1. With the sample audio it was able to isolate the center channel completely, with some overlap between Left/Left surround and Right/Right surround.

    I am not sure about the branding requirements, but if the PCM270x supported dts or dds we would show the trademark on the datasheet.

    Thanks,
    Paul
  • 0 in reply to Paul_Frost
    Prodigy 60 points

    Thanks for your answer. I didn't think it would be an issue, since I'm trying to passthrough, not decode/encode anything. The receiver will do that :)

    In fact, does it not force the chip (or the computer) to decode the 5.1 track and re-encode for stereo?

    Thanks again,

    Amit

  • 0 in reply to A R76
    Prodigy 50 points
    You would think this was a no brainer that if a DAC has SPDIF it should be able to passthrough DTS to a receiver which does the decoding, but I've tried 3 different USB DAC's with spdif that can't and after a lot of online research it seems there are none. It's just a matter of sending an unmodified signal since DTS is compressed, but for some reason this is rare. There was a USB DAC that did passthrough which a lot of people used pre HDMI receivers from Turtle Beach called Advantage Micro II, but it was discontinued a long time ago.
    Unfortunately HDMI is the "solution" but it is such a waste to get rid of a perfectly fine receiver just because it lacks HDMI input.
    Until I buy a new receiver I have to continue using my desktop PC as a HTPC with a 15 year old PCI DAC that has spdif and does passthrough perfectly.
  • 0 in reply to Johan Tenbrink
    Prodigy 60 points

    I still find it hard to believe this is the USB DAC's problem. your 15 years old PC runs Windows XP? XP didn't try so hard to control audio. After all, the application simply needs to pass the bitstream through, and most have exactly such setting to do that.

    I suspect Windows 10 detects this , compares with the declared USB DAC number of channels, and does you a huge favor of reencoding to 2 channels. If so, there should be a way to bypass this, if Microsoft were not trying so hard to hide this.

    I was hoping TI has some connection with the Redmonians..

  • 0 in reply to A R76
    Prodigy 50 points
    God no the PC is not 15 years old just the DAC, the PC is "only" 5 years old, and it runs Windows 10, and passthrough worked fine with both Windows 7 and 8 too on the same machine using the old PCI DAC.

    The HIFIBERRY DAC that a lot of Raspberry Pi users use also has a TI chip if I did my research correctly, PCM5122, and this one does passthrough, which I even have confirmed from my brother who uses one. I didn't have time to do more testing with the 2704 but maybe it would do passthrough with an RPi?
  • 0
    Genius 3945 points
    The reason Windows insists that it's a two-channel device is because that's how the device enumerates. That is, each USB device tells the host what it is and what it supports. It does this through the device's descriptors.

    Now the PCM2704 does allow for some of the descriptors to be changed, but none of those are for the audio streaming interface. So it will always be a two-channel output-only device.

    As for S/PDIF and 5.1 support, S/PDIF is a two-channel-only protocol. TOSLINK on fiber does support more than two channels, but those channels are Dolby-encoded.

    I understand that you want to do a pass-through, but unfortunately USB doesn't work that way. The device has to enumerate as it is for all of the drivers to work.
  • 0 in reply to Andy Peters
    Prodigy 60 points

    Thanks, Andy, that is a great review of the situation.

    Anyone who got a DTS or AC3 mistaken by a receiver to be regular stereo data, knows the horrors of white noise at 0db threatening to bring down the house.

    This also means that 5.1 data is encoded into regular stereo PCM bitstream, so it can go via a medium that was designed to move  CD audio.

    That is also the reason for the 1509.75 kbit/s data rate limit.or am I misunderstanding the way multichannel formats encode via SPDIF?

    http://themediaserver.com/understand-5-1-7-1-surround-sound-htpc-kodi/

    I guess what I need is a media player that can be made to ignore what Windows is telling it, and blindingly transmit this data, for the receiver to decode. Kodi looks promising.