How to prevent Audio HANC completely on Decklink Quad?

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Andrew Devine

  • Posts: 5
  • Joined: Mon Sep 29, 2014 8:48 am

How to prevent Audio HANC completely on Decklink Quad?

PostMon May 18, 2015 1:28 pm

Does anyone know a way to disable SDI audio output from a Decklink Quad card?
System = DesktopVideo 10.4, SDK 10.4, DeckLink Quad, Windows 7.

Without any scheduled (pre-rolled) frames, when a DeckLink channel is started using IDeckLinkOutput::StartScheduledPlayback audio data within HANC is seen (SD PAL Video samples after #719). The same is witnessed using Blackmagic Media Express to play back an imported video file that doesn't have any audio.

IDeckLinkOutput::DisableAudio method always gives me "Access denied" wherever I've tried to use it in my code (before or after Enable video within my initialise, or after starting an output).

Also, I have tried disabling the Blackmagic audio devices within Windows Device Manager and audio ancillary data is still being output.


Nicholas Gill

Blackmagic Design

  • Posts: 169
  • Joined: Mon May 04, 2015 10:28 pm

Re: How to prevent Audio HANC completely on Decklink Quad?

PostThu May 28, 2015 2:03 am

Hi Andy,

It is not possible to completely disable HANC from being output. When there is no audio supplied by the SDK application, the cards will still output audio ancillary data in HANC over SDI and HDMI.

I presume from the description that IDeckLinkOutput::DisableAudioOutput is being called without IDeckLinkOutput::EnableAudioOutput. DisableAudioOutput will return E_ACCESSDENIED if the audio output is not enabled.



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