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ADV7611/ADV7511 Video and Audio Latencies

Hello,

I would like to the understand the basic timing relation between the various Video Signals (Vsync,Hsync,Valid) and the I2S audio signals.

What will be the audio signal behavior when the hdmi input is removed. Whether the I2S data line will send 0s immediately or it will wait till all the audio samples of previous frames are transmitted.

Similarly, what will happen if the HDMI input was removed before a complete frame could be received. How will the audio transmission happen in this case.

Let us assume, FHD @60fps carrying 48KHz audio samples. Theoretically the number of audio samples per video frame will be 800. 

Case 1 -Normal working: When does the ADV7611 chipset start transmitting the audio, for the current frame being received, on the I2S line. It will be helpful if I could get the transmission with respect to the sync signals , for instance - it will start immediately after the vsync deassertion or something along the lines.

Case 2 - HDMI input removal during blanking period: When the HDMI cable is removed during the Vertical Blanking and the previous frame transmission has completed. Will the audio for this frame be received or will it be discarded.

Case 3 - HDMI input removal during active period: When the HDMI cable is removed during the Active Period, will the audio for this frame be received or will it be discarded.

 

For the ADV7511, I would like to understand which audio samples will be transmitted for the next video frame to be sent.

Thanks.

  • Hi,

      When transmitting video data across the TMDS interface, it is necessary to have an Hsync, Vsync, and Data Enable (DE) defined for the image.
     In the Data Island period, audio samples & infoframes data will be transmitted on the TMDS lines and this data Island will occur during any horizontal or vertical blanking period.

    Case 1 -Normal working: When does the ADV7611 chipset start transmitting the audio, for the current frame being received, on the I2S line. It will be helpful if I could get the transmission with respect to the sync signals , for instance - it will start immediately after the vsync deassertion or something along the lines.

        The part will be outputting audio in the I2S lines as soon as the PLL locks on normal working condition.

     Case 2 - HDMI input removal during blanking period: When the HDMI cable is removed during the Vertical Blanking and the previous frame transmission has completed. Will the audio for this frame be received or will it be discarded.

         As stated earlier during blanking period the audio samples & infoframes data will be transmitted on the TMDS lines, So it will be discarded if we remove the HDMI input during blanking period.

    Case 3 - HDMI input removal during active period: When the HDMI cable is removed during the Active Period, will the audio for this frame be received or will it be discarded.

           I believe Yes, audio will be received on the I2S lines. DE indicates an active video & during this interval the TMDS lines will have video on them when DE is low TMDS will carry infoframe and audio packets. Please prob and check the corresponding audio pins.

          Please note audio clock is derived from the video clock.  If there is no input video clock, there will be no audio clock So It is not possible to send audio without an external video input.Since audio clock is derived from the TMDS clock.

    Thanks,

    Poornima