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VPFE Buffers: Capture vs. Output?

Tom Hanson
Intellectual 920 points

Where can I find a discussion (documentation?) of the difference between "capture" buffers (V4L2_BUF_TYPE_VIDEO_CAPTURE)  and "output" buffers(V4L2_BUF_TYPE_VIDEO_OUTPUT) provided by the VPFE? For the DM365 if possible.

What I'm looking for is pretty basic: what data goes into which type of buffers and how do you get to it.  I'm getting it figured out by sifting through the various documents and sample code, but it shouldn't be this hard. 

More specifically, I'd also like to know how/where to access the "second output" data buffers.

Thanks in advance!

  • 0
    TI__Mastermind 37340 points

    Tom,

    V4L2 is a Linux standard for video capture/display buffers; hence you will not find much documentation included in the TI collateral because this is not our standard, but rather an industry standard.  You are correct that it should not be this hard; perhaps it appears hard because you are only finding bits and pieces in the software/docs we provide since we assume you can get V4L2-specific info on the web.

    That said, there is some documentation for various Linux standard drivers under the Linux kernel we provide (look under .../ti-davinci/Documentation)

  • 0 in reply to Juan Gonzales
    Intellectual 920 points

    Thanks, I'll take a look on the web.

    Since the provided software solution has been pieced together from multiple sources, perhaps a guide should be provided that identifies what pieces came from where, and where the documentation for each can be found. 

    Or perhaps TI could gather together a library so that each developer doesn't have to do it themselves?

  • 0 in reply to Tom Hanson
    TI__Mastermind 37340 points

    This is great feedback; I am thinking a wiki article may be the fastest way to get this sort of information out to customers.  I will put it on my list of things to do and will likely work on it when I get back from vacation next week.

  • 0 in reply to Juan Gonzales
    Intellectual 920 points

    Wonderful idea! 

    While you're at it, could you come up with a summary of all of the various pieces of demo code?  Including little things like:
    - dvsdk_demos use the DMAI API to manipulate encoders
    - dvtb uses the Codec Engine API to manipultate encoders
    and whatever it is that the PSP Examples do with encoders.

    That would speed things up for newbies such as myself who are trying to find/exercise/add particular features.

  • 0 in reply to Tom Hanson
    TI__Mastermind 37340 points

    sure thing; I will post link here when I complete the article so you (or others) can review it and perhaps offer some feedback.

  • 0 in reply to Juan Gonzales
    Expert 1225 points

    Have you finished the wiki DOC ? because I am not able to get the v4l2-vpfe connetion and video buffer handling codes  :)

  • 0 in reply to Digant Desai
    TI__Mastermind 37340 points

    Hi All,

    So the original idea behind the wiki was to summarize the contents in the DVSDK to educate users on what is included and hoepfullly save users some ramp-up time; there is a good amount of documentation included but no easy way of knowing is there unless user pokes around, which can be very time-consuming for new users.  To help, we have created the following wiki article which can evolve over time based on feedback.

    http://wiki.davincidsp.com/index.php/DVSDK_Contents

    As you may see, there are links to other wikis for more in-depth information on particular topics such as DMAI, DVTB...  It can be difficult to cover all programming aspects of a device, but where it makes sense we can continue to add valuable information based on your feedback.

    I hope this helps.