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ADV7403 ADV7842 and ADV7850 chips

I am about to start a composite and s-video signal digitization project. Before i get started i need to establish which of your chips to use. I may as well start with what ever your current chip is as I may have been reading old internet webpages.

I have been looking keenly at your ADV7403 chip. Can you tell me whether this has been updated by your ADV7842 and ADV7850 chips and are there even any later chips than these? I could have easily missed something on your website.

Outputs required are digital(s-pdif)  for PC card capture and HDMI for the TV.  I will also require the 3D comb filter and TBC facilities mentioned for these chips in your datasheets. I will also require stereo inputs for the HDMI TV output.



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  • FormerMember
in reply to RagTag +1 verified

Audio CODECs can be found here

CODECs come with output DACs but you don't have to connect or use them them.  The key you are looking for is I2S bus…

  • FormerMember
    0 FormerMember

The ADV7842 has an input HDMI port and the ADV7850 has both input and output HDMI ports.  The analog sections are very similar. Both have 3D comb and TBC.  TBC was used to correct issues with old VCRs so I'd be surprised if you need it for modern systems.

The ADV7403 does not handle HDMI directly.  It only has a digital input port, not HDMI decoding.

If you need HDIM input and output plus analog decoding plus audio insertion I'd look at the ADV7850 single chip solution.  The ADV7842 is great where you need HDMI input and analog decoding feeding an FPGA or a ADV7511.  Note  these chip only handle HDMI 2.0 spec.  Do you need to handle HDMI 2.1?

Also keep in mind you will need to be an HDMI and HDCP adopter to use these chips with HDCP keys.

If you can include a list of supported inputs and outputs with formats required we can point you to a possible solution. 

  • Thank you very much for your informative reply. What i need to do first is to get the chips sorted out.

    input signals

    I have 2 input analogue Video signals to process:-

         1) composite (CVBS) from a laserdisc player
           1.1) Hence the need for an excellent comb filter to split this composite signal into its S-Video Y & C signals.

         2) S-video signal from VHS players
            2.1) And from the Lasedisc Y&C signal just mentioned
            2.2) VHS players - Hence the need for a TBC.

    Output signals

     I need 2 output signals:-

         1) Digital output signal for input into a computer PC capture card.
         2) HDMI output signal for input into a TV
            2.1) This will also need stereo input sockets to take the audio signal from the 2 input sources above.  

    What Chips do i need?

    How does the above translate into chips? And this is where i need your help. Can you sort me out here.    

    first possibility. Have 2 seperate chips in use on 2 seperate boards:-

         1) ADV7842 to take the input sources listed above and create a digital output signal for input into a computer PC card .
         2) ADV7850 to take the input sources listed above and create an HDMI signal for input into a TV.

    second possibility. Have 2 connected chips available:-

         1) ADV7842 to take the input sources listed above and create a digital output  for input to a PC card and ADV7511
         2) ADV7511 to take the digital output from the ADV7842
            2.1) to create the HDMI output signal for input into a TV.       

    I have a problem with the ADV7511 - its datasheet does not show an HDMI output connection. Can you update me on this.

    HDMI 2.0 will do the job very nicely.

    Hope the above makes sense. If i have anything wrong then please correct me on it.


  • FormerMember
    0 FormerMember in reply to RagTag

    Your option 2 is the way to go, ADV7842 -> ADV7511, Digital capture.

    Digital capture card is not very clear, does it capture CMOS digital bus or something else.  Normally PC capture cards have analog or HDMI inputs, not a digital bus.  Need a bit more architectural information here.

    The EVAL-ADV7842-7511 show you how to implement that solution.  Check out these links

    They'll show you how to get started with the ADV7842-7511 .

    You will also need an audio to I2S converter to inject the audio into the ADV7511 I2S port.

    The ADV7511 has a TMDS output which is the HDMI output.  Check the reference schematic to see how it's done.

    The ADV7842 also has an HDMI input which you could use as a normal input port, maybe as a test input from a PC.

    Other chips like the ADV7181D will decode your sources but don't have the TBC feature.

  • Thank you very much for the reply which has given me  a lot to digest. There are some areas i didn't know existed.  

    Thanks for raisng the PC card question.  I need to look further into the PC capture card end of the business. This is not something i have done as yet, I

    just assumed that there would be PC Card that takes digital input. Whether I expected your digitizer chip  to combine the audio signal  into the digital

    signal or Whether i was expecting th PC card to take the audio signal, digitise it and mix it with the digital signal, i just don't know at this stage.  I

    know i have in mind that the PC card would capture RAW video footage into a .DV file, ie no codecs at this stage. I know this would produce large files, but

    modern PCs should easily cope with this. Maybe i have a lot to learn. As for audio, i would like to be able to capture, whatever the method, at 96htz/24bit

    at least.  

    In the meantime can you answer a question on TBCs. This time about the ADV7842 TBC as TBCs are important for VHS cassette playback.

    Does the ADV7852 TBC function as as internal or external TBC?

    On VHS players the internal TBC cleans up TV display artefacts, all squiggles and other aberrations that often show on the TV.

    The external TBC is purely for the PC Capture card and is neccessary to replace  the current timestamps on the analogue signal with precise timestamps required by the PC capture card  and also to release the signal at an even rate for the PC capture card. Without an external TBC the PC capture card may very well fail to capture the video.

    These are my interpretations of the large quantity of notes I have on TBCs, i hope my interpretations are correct.

    Full frame TBCs are better than line ones.  

    My own tests have shown however, that with the  VHS internal TBC switched on, that LCD TV picture quality is pleasantly improved with an external TBC between the VHS player and LCD TV.  That is, the LCD TV likes a decent, well sorted signal.  



  • FormerMember
    0 FormerMember in reply to RagTag

    1) ADV7842 and ADV7850 have internal TBC and use external SDRAM for temporary frame storage.

    2) TVs and HDMI sinks like stable time based video.  VCR has some time jitter in the frame rate.  TBCs (Time Base Correction) captures the input, stores it in the SDRAM frame buffer and outputs at a stable frame rate.  Full frame TCBs are better.

    3) I don't know of any digital bus PC capture cards.  All I've seen have analog or HDMI inputs.  (Capturing a  video digital bus over a cable would be painful.)

    4) Another option is run every thing through the 7842 so the TBC can be used then have 2 ADV7511s, one going to the TV and the other going to the PC capture card.

    5) My next suggestion is draw up a simple diagram showing the video and audio signal flow paths.  From this you can determine the chips to use and define various use cases.

    Right now it seems to make more sense to run everything into the ADV7842, let it do the TBC, then have 2 ADV7511's, one sent to the PC, the other goes to the TV directly.

    Of course audio would need to buffered and split the same way.

    When you get to this point you can get an EVAL-ADV7842-7511P board to test things out.  Only ~$200.

  • It sounds like the TBC on the ADV7842 is acting like an external TBC and correcting the timestamps (ie jitter) rather than acting like  the internal TBCs on VHS players such as the American Panasonic AG-1970 and AG-1980 VHS players which correct the picture.

    One last question on the ADV7842 TBC.  How does the ADV7842 TBC operate:-

    1) does use an input a digital signal that it performs corrections on? Does it output a digital signal?

    2) or does it work in the more traditional VHS TBC sense of converting the Analogue signal  to a digital signal, performing the corrections on the digital signal and then converting the corrected digital signal back to an analogue signal for output (A-D-A).

    CVBS(composite) input signal on the ADV7842 -  are the 2D and 3D comb filters applied to this signal before or after the signal is digitised?.

    After what you have said i think I am really going to have to look into PC capture cards. It could alter what i am thinking about entirely.

    I like what you say about the price of the evaluation board.   

  • FormerMember
    0 FormerMember in reply to RagTag

    I might not understand your definition of internal and external.  It really doesn't matter as long as you get the results you are looking for.

    Check out the detailed functional block diagram.  The ADV7842 digitizes the analog input, runs it through a series of  processing modules and outputs digital data.  These modules include 3D comb and TBC.  It uses the external SDRAM for frame and line storage for the TBC and 3D comb functions.

    The ADV7842 has two video path depending on the input.  The SDP handles CVBS video while the CP handles other higher formats, normally progressive.

  • I think my questions are to getting to detailed so lets get back to the evalution board.

    I am just trying to get some idea of how the ADV7842 works and the order of processing. Things are not so visible on a chip as they are with hardware.  

    hope these questions are a lot easier. I have 10 questions, here is the first 5 and then maybe down to biz:-

        1) When an S-video signal is input into the evaluation board are the comb filters used?

        2) can the TBC be turned of if required/ preferred.
        3)  How ar the settings changed. All the setting and controls eg output bit rate selection, 4.2.2 or 4.4.4, appear to be controlled by jumper switches. Can these be bypassed/ overidden  by switches on the box containing the evaluation board to give easier selection facilities or does the lid have to come off the box to change the jumper switches.

        4) MAcrovision 1,2 and 3, CGMSa - is there any contact points to which LED lights can be attached, to show which level of macrovision is present, if any.

        5) PAL/ NTSC/Secam - is there any contact points to attach LED lights to show which of these formats is in use.

  • Lets try and clear up interenal and external, we both have different meanings for these words.  Nothing for you to answer here

    Internal and external TBCs are both associated with VHS players and perform different functions but to do their correction they both convert the analogue (composite or s-video) from analogue too digital and then back to to analogue (A-D-A). Corrections are carried out on the intermediate digital signal. If both of these types of TBCs are in the system then thats 2 lots of conversions.  Both the A->D and the D->A conversations cause some loss to the picture quality  and the internal TBC is often accused of softening the TV picture.  

    INternal TBC
    An internal TBC comes as part of the VHS player, that is, it is part of, and internal to, the product. Hence "internal". There is a switch on the control panel to turn it on or off as required. It was also associated with a DNR which might have its own switch or is combined with the TBC. As i stated the  purpose of the internal TBC was to clean  up the analogue signal  of artefacts caused by the vhs player and or the vhs cassette before it was transmitted to the TV.

    External tbc.
    The external TBC is a seperate item to the VHS player and sold seperately.  It is outside the VHS player, hence "external". Analogue video cables from the VHS player  are routed to it and its ouput analogue video cables are routed to a PC capture card. Its sole purpose is to tidy up the analogue signal (composite and s-video) to remove jitter and produce a nice even signal for input PC capture cards are that are more demanding on the presision of the signal than a TV is.

    Note that the DNR mentioned may also perform its own A-D-A conversion sequence on the analogue signal.

    These A-D-A conversions suited the equipment of 20 years ago but now are just archaic. Once the signal is in the digital domain is should just stay there, thats my opinion. Modern equipment can cope with it and each conversion creates some loss to the picture quality.

    What i was trying to find out was how much the ADV7842 TBC can dispense with these conversions and the  A-D-A sequence of conversions, and whether it just takes a digital signal produced elswhere in the ADV7842, corrects it, and outputs the digital signal for processing elsewhere on the ADV7842. That is, its dispensed with the now uneccessary D->A conversion and subsequent A->D by the LCD TV which should help TV picture quality.   

    From what you have said the ADV7842 TBC performs the functions of, in the sense that i am using the word "external",  an external TBC. That is, it cleans up the  overall signal for  the PC capture card but does not clean up the sqiggles and other artefacts that can appear on a TV.  This means that the  VHS players internal TBC ( + DNR) will still have to used to do this job.  

    I am beginning to sound like an expert which i am not.

    OK, enough of that and on with the biz    

  • FormerMember
    0 FormerMember in reply to RagTag

    As you stated, every A-D and D-A introduces a bit of loss.  The fewer domain conversions you have the better off you are.

    The first thing the ADV7842 does to analog inputs is digitize them with a 12-bit ADC.  From that point onward all processing is done int 12-bits in the digital domain. The  processing modules are basically all in series with each module having a bypass path so each module can be included/excluded into the path as needed.  This includes the comb filters, TBC, peaking, color space conversion, output format, de-interlacing....

    Please look at the detailed feature diagram in the data sheet

    From your explanation the ADV7842 TBC would be an external TBC to the VCR and the final TBC in the system.

    All these controls are controlled by register accessed over an I2C interface.  We provide scripts for various input/output formats configurations.  AvesBlue is a tool to access the evaluation board over a serial port, displays all the registers and allows you to run scripts and toggle the control registers.  Download it and try it out.  You can use the NULL driver to see the windows in action if you don't have an eval board.

    Note the EVAL-ADV7842-7511P has two modes of operation, one where AvesBlue and scripts control everything and one where the embedded code in the BlackFin controls chip configuration as inputs and outputs are plugged in/out.

    The ADV7842 does detect macrovision.

    I hope this answers some of your questions