Camera Preview Frame Stride

[steve2641]

Hello,

I have a question about the preview frames that can be returned by
Camera Services to the applications. There seems to be two different
means of returning the frame, copied or not copied, ignoring the one
shot case which is not important for this discussion. In both of
these cases, the stride of the buffer does not seem to be taken into
account. The application will need the stride in order to properly
parse the buffer, unless the width of the frame data and the stride
are equal.

If one were to use hardware or a software feature which pads the
frame, the Surface Flinger would be able to properly parse the buffer,
since it has the width stride, but I have not found any place where
the application can get this key piece of data.

This issue could be quickly solved for the cases where a copy of the
preview buffer is requested by the application. In this case the
copyFrameAndPostCopiedFrame() function would just need to copy the
buffer with the knowledge of the stride. The stride could be stored
off when the Surface Flinger is given the heap and then reused in this
function to properly copy the preview data from the preview frame to
the buffer that will be passed to the application.

In the case of returning the actual preview memory, the issue gets
more complicated. The application would need to be given (maybe in
the callback) the actual frame stride. I'm not sure how the
application could parse the preview frame without it.

One feature that will tend to cause preview frames to be padded is
image stabilization, but I can also imagine hardware limitation that
may also cause padding.

Thanks,

Steve.

[Dave Sparks]

I agree we need some work in this area.

We get around the problem right now by forcing the stride to be the
same as the display. On G1, this means preview must always be a
multiple of 16 pixels.

[steve2641]

Per Dave Sparks request, bug 1986 was entered for this issue.

On Jan 28, 1:58 pm, Dave Sparks <davidspa...@android.com> wrote:
> I agree we need some work in this area.
>
> We get around the problem right now by forcing the stride to be the
> same as the display. On G1, this means preview must always be a
> multiple of 16 pixels.
>
> On Jan 26, 11:54 am, steve2641 <steve2...@gmail.com> wrote:
>
>
>
> > Hello,
>
> > I have a question about the preview frames that can be returned by

> >CameraServices to the applications.  There seems to be two different

> > Steve.- Hide quoted text -
>
> - Show quoted text -