Low sample frequency from Blu-ray music disks


  • On Monday this week I received my new Magnetar UDP800 MKII and I updated the firmware to version 987. One of the main reasons I made this purchase was to play my collection of Blu-ray albums with high-resolution stereo tracks, and high-resolution flac files through the USB port.

    I have the player connected to a Schiit Gungnir 2 DAC using a new digital coaxial cable. Shiit provides an iOS app that allows me to monitor the sample frequency of the source signal.

    When I play high-resolution flac files through the USB port on the player (e.g., Neil Young Archives at 192kHz / 32-bit) my DAC shows the 192kHz sample coming through, and I see the sample frequency change appropriately when I play flac files with different sample frequencies.

    When I play Blue-ray disks — all contain 96kHz / 24-bit files — the DAC shows only a 48kHz sample rate.

    Blu-ray disks tested include:

    • The Alan Parsons Project — Tales of Mystery and Imagination — 96kHz / 24-bit stereo track
    • Big Big Train — The Likes of Us — 96kHz / 24-bit LPCM stereo track, Blu-ray format: BD50
    • Steven Wilson — The Overview — 96kHz / 24-bit stereo track

     

    My Audio settings on the player are:

    • Spdif: Bitstream
    • HDMI: PCM
    • Max Sampling Frequency: 192kHz
    • DRC: Auto

    ...and I've tried adjusting the settings with no effect.

    I’m not sure how to get the full 96kHz sample frequency from these Blu-ray disks to my DAC. Am I doing something wrong? I would appreciate any advice.

    The fact that the flac files seem to work fine seems to suggest that the issue isn't with the Audio settings, DAC, or coaxial cable.



  • What you are seeing is expected behavior when playing Blu-ray discs through the coaxial (S/PDIF) digital output.

    While Blu-ray discs can contain 96kHz / 24-bit LPCM stereo tracks, the S/PDIF (coaxial and optical) digital output standard is bandwidth-limited and, due to Blu-ray licensing and copy-protection rules, most Blu-ray players are required to downsample disc-based LPCM audio to 48kHz when output over S/PDIF.

    To obtain the full 96kHz / 24-bit signal from Blu-ray discs, the audio must be sent over HDMI, where higher sample rates are permitted. From there, you would need either:
    • An AVR or processor with high-resolution DACs, or
    • An HDMI audio extractor capable of outputting high-resolution PCM

    Thanks


  • Thanks for explaining the reason for the results I'm seeing and for pointing me in the right direction. Most appreciated!


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