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TFP403: Input Signal Questions

Richard Elmquist
Mastermind 45250 points
Part Number: TFP403
Other Parts Discussed in Thread: TFP501

I have a customer asking the following questions concerning the TFP403:

What happens on the output if the TMDS input (normally from a DVI source) contains embedded audio (as though it was coming from a HDMI source)? Also what happens on the output if the input contains HDCP?

Please let me know if you have any additional questions for the customer.

Thanks for your help with this!

Richard Elmquist

  • 0
    TI__Mastermind 45250 points

    Has anyone had a chance to look at the request above?

    Can you give a time frame as to when you might be able to provide the information?

    Thanks for your help with this!

    Richard Elmquist

  • 0 in reply to Richard Elmquist
    TI__Guru* 76130 points

    Hello,

    The TFP403 is only a de-serializer, the audio signal is transmitted during the blanking periods in which the DE signal is low, thus the QE[], QO[] outputs will be low.

    The TFP403 does not support HDCP so the Video Source won't be able to establish a link with the TFP403, if they want HDCP support we can recommend the TFP501 which is pin-to-pin compatible with the TFP403.

    Regards

  • 0 in reply to Elias Villegas M.
    TI__Mastermind 45250 points

    Elias,

    Thanks for your response!

    I will let you know if the customer has any further questions.

    Thanks again!

    Richard Elmquist

  • 0 in reply to Richard Elmquist
    TI__Mastermind 45250 points

    Elias.

    The customer has sent the following comments:

    So what they are saying is that if audio is supplied it should not affect the TFP403 output? 

    We have a design (not in a monitor) that is using the TFP403.

    It looks only at sync, de (to qualify valid data on qe), and scdt outputs. 

    When scdt becomes valid, it uses sync to reset counters which count the number of pixels in a line and the number of lines in a frame to determine for itself if the image is stable (constant number of pixels in the lines and number of lines in a frame). When it determines the image is stable it will assert its own valid signal. If the number of pixels and number of lines varies, then the image is not considered to be stable. Also if scdt becomes invalid, the image is also not stable. 

    We have seen different results when audio is embedded into the incoming TMDS.

    Case #1: The image is determined to be stable but the resolution that is detected is off by a few pixels and lines.

    Case #2: The image never becomes stable. 

    If we run the TMDS ( HDMI in) through a box that extracts the audio from the video (DVI out), both the above cases result in a stable image and, for case #1, the actual resolution that is detected is not off, but what was expected. 

    So our conclusion is that the TFP403 output DOES get affected by embedded audio. 

    What comments to the factory engineers have based on what I have said above?

    Is the customer correct in his statements? Please let me know if you have any questions for the customer.

    Thanks for your help with this!

    Richard Elmquist

  • 0 in reply to Richard Elmquist
    TI__Mastermind 45250 points

    Elias,

    Have you had a chance to look at the customer's further questions?

    Thanks for your help with this!

    Richard Elmquist

  • 0 in reply to Richard Elmquist
    TI__Guru* 76130 points
    Hello,
    It is possible the the embedded audio is shifting the blanking periods which would explain the issues.
    We need to see how the serial data is encoded in the GPU. What they are doing: remove the audio component, sounds like a robust workaround, if they can do that I would recommend so.

    Regards
  • 0 in reply to Elias Villegas M.
    TI__Mastermind 45250 points

    Elias,

    Thanks for your response!

    I will contact the customer and ask them you questions.

    I will respond back as soon as I can.

    Thanks for your help with this!

    Richard Elmquist

  • 0 in reply to Richard Elmquist
    TI__Mastermind 45250 points

    Elias,

    The customer has come back with this response:

    We have already proven that it works fine when the signal goes through a device that strips off the audio.

    I was just asking a specific question as to what happens to the output when audio is present.

    The answer I believe I am getting from you is a more general if audio is present it can affect the output.

    I was just hoping you would be more specific as to exactly what the output does instead of a could be.

    We have no idea how the audio is encoded as it is coming from any device in the world that is not of our design.

    Our design will lock on the TFP403 output (but with the wrong resolution) when connected to some devices.

    With other devices it does not lock.

    Are there any further comments you can make on this? It seems that they really have no way to strip the audio. This appears to me to be a problem and you have stated that is can affect the blanking period and thus effect the timing of the signal. To me it sounds like they need to try and process the signal first instead of just sending any signal through. Can you comment on this? Is there anything we can do to help? Is there another device that might work better.

    Thanks for your help with this!

    Richard Elmquist

  • 0 in reply to Richard Elmquist
    TI__Mastermind 45250 points

    Elias,

    Have you had a chance to look at the comments from the customer?

    Please let me know if you have any response for this.

    Thanks for your help with this!

    Richard Elmquist

  • 0 in reply to Richard Elmquist
    TI__Guru* 76130 points
    Hello,
    Just to be clear, the TFP403 does not support audio in the way that it won't decode any audio signal, it will only decode the video signal, this is why we recommend to send only video signal (the audio component won't pass through anyway).
    I think you have proven that the audio signal is causing issues, I believe the audio signal is taking too long(audio can be transmitted at several frequencies much more slower than the video signal) on the blanking period and thus causing the TFP403 to "see" the link inactivity due to the lack of change on DE status. Again, we would have to look at the video/audio encoding and blanking intervals.
    If you can't get the GPU to send only video then I'll suggest to remove the audio component.
    Regards
  • 0 in reply to Elias Villegas M.
    TI__Mastermind 45250 points

    Elias,

    Thanks so much for your help!

    Have a great day!

    Richard Elmquist