Multichannel PCM audio passing through HDMI

Hi everyone !

First post here so I hope I'm relevant. I hope I'm not going to be too messy in my explanations, I'll try my best.

First of all, the context : We have to display 3 different but synced video media on 3 separate screens with a 7.1 audio diffusion, with BrightSign units (XD1034). The video syncing is not my issue, but the sound is.

We wanted to get the multichannel PCM audio through the HDMI, then converted to SDI, to eventually  convert SDI to Audio with a BlackMagic SDI - Audio Converter and have our multiples channels in analog or AES separated from the video : 

I didn't encode the video, but it was converted from a ProRes file to an H265 file with multichannel PCM audio, at a correct bitrate.

So, I made a test ! The video plays alright, but no sound anyhow at the output of the audio / SDI with a BrightSign setup. Just the vast, noisy silence of an electronic world birthed by the testing speaker.

I tried playing the original ProRes file with a BlackMagic Hyperdeck, and here the SDI / audio converted worked well, I managed to listen to every separate audio channel, so I know the BlackMagic converter works. 

So, do you think there's any way I can make the BrightSign setup eventually work ? 

It is very possible that we messed the encoding, or anything else in the process, but I'm not at my ease enough is those subjects to find our mistake(s) ; hence my distress call here :D

Thanks for the time you took reading this !


  • 0
    Bright Scripters

    Encoding audio to AC3 or EAC3 as 7.1 might be a better direction over multichannel PCM.

    You'd then need to decode 7.1 from HDMI to discrete audio channels.

    Use of SDI might be an overkill in this context.


  • 0
    Ed Williams

    This was an issue I raised with BS back in 2020. I've had to now buy a Denon MP3 playback unit and output from that across multiple channels :( Then also add a Arduino into the mix to control it. Not great.

    Apparently the BrightSign used to be able to send PCM across the HDMI but it isn't working on the currently fleet. :/ Be interested if you find a way round this. We tried every combination of encoding and audio outputs on the BS units and no luck.

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