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How to mute video and audio when starting HDCP authentication on ADV7626

Category: Datasheet/Specs
Product Number: ADV7626

In "9.14.4 AV Mute" on page 226 of the data sheet, it is stated that it is not recommended to perform AV Mute for HDCP authentication.

It is stated that video and audio should not be sent to Tx before HDCP authentication.

Even if I manipulate the blackout at 0x9E[5:4] and the audio input selection at 0x0A[6:4], it doesn't work.

Which register will I manipulate to achieve this?

  • Hi,

    AV Mute can be enabled once HDCP authentication is completed. This can be used to maintain HDCP synchronization while changing video resolutions. But it is not recommended to rely on AV mute to avoid sending audio and video during HDCP authentication.

    AV Mute also pauses HDCP encryption.
    You can mute and unmute audio and video by setting below registers.
    Dharani S
  • Hi,

    "But it is not recommended to rely on AV mute to avoid sending audio and video during HDCP authentication."

    ↑ states that AV muting is not recommended during HDCP authentication.

    Which register should I manipulate to prevent video and audio from being transmitted during HDCP authentication?

  • Hi,

    To add on with my previous post, one purpose of the AV Mute is to alert the Rx of a change in the TMDS clock so the Rx can mute audio and video. AV Mute also pauses HDCP encryption, so the HDCP link is maintained while the TMDS clock is not stable. It can also be used in general to tell the sink to mute audio and video. AV Mute is not sufficient to hide protected content, because the content is still sent even when AV Mute is enabled.

    We can prevent audio at Tx side without muting directly. Select the transmitting audio as 'No audio' by setting TXA_AUDIO_SOURCE_SEL[2:0] (or TXB_AUDIO_SOURCE_SEL[2:0]) as 000.

    There is no register setting for avoiding video at Tx without muting.

    VIDEO_OFFSET_CTRL: This signal is used to control the video offset control for U and V channels and black image control to force black video data out of the TX.

    If you want to mute the Video (i.e Black image to be sent across the HDMI link), please enable the 'VID_ADJ_EN' register before configuring the color control registers. For pure black video output, we need to change the contrast, saturation, hue and brightness value registers as zero.


    Dharani S