On Thu, 25 Oct 2001, Sottek, Matthew J wrote:
> Ok, I slightly modified the idea to take care of this too. I must
> say, I really really like this one.
>
> #define XV_TOP_FIELD 0x01
> #define XV_BOTTOM_FIELD 0x02
> #define XV_FRAME (XV_TOP_FIELD | XV_BOTTOM_FIELD)
> #define XV_HOLD 0x04
>
> Mostly the same behavior as before, but now we really use these as
> bitfields. When the XV_HOLD bit is ON, the data is not updated
> onscreen at the end of an XvShmPutImage. It has to wait until the
> HOLD bit is removed.
> Here is the change, Bits 0 and 1 indicate the fields that will be
> updated with the next XvShmPutImage. The image position and scaling
> information are always updated. Here are some example uses.
>
> Default Case: (Works just like it does now)
> XV_FRAME_TYPE = XV_TOP_FIELD | XV_BOTTOM_FIELD (Default)
> XvShmPutImage: Both fields are updated from the XvImage, the data
> is updated asap onscreen since the HOLD bit is not on.
>
> Interlaced Video:
> XV_FRAME_TYPE = XV_HOLD | XV_TOP_FIELD | XV_BOTTOM_FIELD
> XvShmPutImage: The top field and bottom field are updated from the
> XvImage. The position, size and scaling information are updated
> from the call, but the overlay is not updated onscreen.
XV_TOP_FIELD | XV_BOTTOM_FIELD is redundant. You can't
not copy both fields.
> XV_FRAME_TYPE = XV_TOP_FIELD
> The overlay is updated with the latest information and set to
> show only the top field. The onscreen update happens asap.
> XV_FRAME_TYPE = XV_BOTTOM_FIELD
> The overlay is set to show the bottom field and the onscreen update
> happens asap.
>
> Paused Video:
> Loop:
> XV_FRAME_TYPE = XV_HOLD
> XvShmPutImage: NO Fields are updated from the XvImage, but the
> position and scaling information are taken from the call. The
> overlay is not updated onscreen.
> XV_FRAME_TYPE = XV_TOP_FIELD
> On Screen changed happen asap.
> goto Loop
This is confusing. I don't understand what you are trying
to do here.
Mark.
>
> Paused Video (Better way):
> Loop:
> XV_FRAME_TYPE = 0x0
> XvShmPutImage: NO Fields are updated from the XvImage, the position
> and scaling information are updated. The HOLD bit is not set so
> overlay is updated asap. This means that for a pause you just set
> The frame type to 0 and continue with puts as normal. No data
> copying takes place.
> goto Loop
>
>
> Field at a Time Interlaced:
> XV_FRAME_TYPE = XV_HOLD | XV_TOP_FIELD
> XvShmPutImage: Only the top field is read from the XvImage. This is
> done by taking the first line and then skipping every other line.
> The position, size and scaling are updated from the call.
> XV_FRAME_TYPE = XV_TOP_FIELD
> Update on screen happens asap.
> XV_FRAME_TYPE = XV_HOLD | XV_BOTTOM_FIELD
> XvShmPutImage: Only the bottom field is read from the XvImage.
> Position, size and scaling are updated but not onscreen.
> XV_FRAME_TYPE = XV_BOTTOM_FIELD
> Onscreen update happens asap.
> Repeat.
>
>
> -Matt
>
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