Hi Hans, On Tue, Jun 25, 2013 at 11:02:51AM +0200, Hans Verkuil wrote: > On Tue 25 June 2013 10:21:19 Sakari Ailus wrote: > > Hi Hans, > > > > On Mon, Jun 24, 2013 at 02:48:15PM +0200, Hans Verkuil wrote: > > > Hi all, > > > > > > While working on extending v4l2-compliance with cropping/selection test cases > > > I decided to add support for that to vivi as well (this would give applications > > > a good test driver to work with). > > > > > > However, I ran into problems how this should be implemented for V4L2 devices > > > (we are not talking about complex media controller devices where the video > > > pipelines are setup manually). > > > > > > There are two problems, one related to ENUM_FRAMESIZES and one to S_FMT. > > > > > > The ENUM_FRAMESIZES issue is simple: if you have a sensor that has several > > > possible frame sizes, and that can crop, compose and/or scale, then you need > > > to be able to set the frame size. Currently this is decided by S_FMT which > > > > Sensors have a single "frame size". Other sizes are achieved by using > > cropping and scaling (or binning) from the native pixel array size. The > > drivers should probably also expose these properties rather than advertise > > multiple frame sizes. > > The problem is that from the point of view of a generic application you really > don't want to know about that. You have a number of possible framesizes and you > just want to pick one. > > Also, the hardware may hide how each framesize was achieved and in the case of > vivi or mem2mem devices things are even murkier. > > > > maps the format size to the closest valid frame size. This however makes > > > it impossible to e.g. scale up a frame, or compose the image into a larger > > > buffer. > > > > > > For video receivers this issue doesn't exist: there the size of the incoming > > > video is decided by S_STD or S_DV_TIMINGS, but no equivalent exists for sensors. > > > > > > I propose that a new selection target is added: V4L2_SEL_TGT_FRAMESIZE. > > > > The smiapp (well, subdev) driver uses V4L2_SEL_TGT_CROP_BOUNDS rectangle for > > this purpose. It was agreed to use that instead of creating a separate > > "pixel array size" rectangle back then. Could it be used for the same > > purpose on video nodes, too? If not, then smiapp should also be switched to > > use the new "frame size" rectangle. > > The problem with CROP_BOUNDS is that it may be larger than the actual framesize, > as it can include blanking (for video) or the additional border pixels in a > sensor. I don't think it should include anything else than just the image. Blanking isn't valid image data, and I'd also leave any possible borders out: this is hardly interesting to the user, nor is really part of the image. That's what the user expects, right? The rest can't be meaningfully processed in anyway by hardware blocks, which would mix badly with configuring the pipeline from the user space. A lower level mechanism is needed: frame descriptors. > I would prefer a new selection target for this. It was decided to use the crop bounds for the purpose a few years back, and I don't see a need to change it. (I actually was for having such a rectangle back then, but the rough concensus was different. :)) -- Kind regards, Sakari Ailus e-mail: sakari.ailus@xxxxxx XMPP: sailus@xxxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
