Hi Sakari On Fri, 8 Nov 2024 at 10:30, Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx> wrote: > > Hi Dave, > > On Thu, Nov 07, 2024 at 12:43:52PM +0000, Dave Stevenson wrote: > > Hi Sakari > > > > On Fri, 1 Nov 2024 at 08:48, Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx> wrote: > > > > > > Hi Jai, > > > > > > On Tue, Oct 29, 2024 at 02:27:36PM +0530, Jai Luthra wrote: > > > > From: Dave Stevenson <dave.stevenson@xxxxxxxxxxxxxxx> > > > > > > > > The HBLANK control was read-only, and always configured such > > > > that the sensor HTS register was 3448. This limited the maximum > > > > exposure time that could be achieved to around 1.26 secs. > > > > > > > > Make HBLANK read/write so that the line time can be extended, > > > > and thereby allow longer exposures (and slower frame rates). > > > > Retain the overall HTS setting when changing modes rather than > > > > resetting it to a default. > > > > > > It looks like this changes horizontal blanking at least in some cases. Does > > > this also work as expected in binned modes, for instance? > > > > > > Many sensors have image quality related issues on untested albeit > > > functional line length values. > > > > > > So my question is: how has this been validated? > > > > Validated by Sony, or others? > > I've tested a range of values in all modes and not observed any image > > quality issues. > > Somehow at least. :-) > > > > > From previous discussions with Sony, they always provide their big > > spreadsheet of register values for the specific mode and frame rate > > requested. I don't think they even officially state that changing > > VTS/FRM_LENGTH_LINES to change the framerate is permitted. > > There are some Sony datasheets (eg imx258) that state "set to X. Any > > other value please confirm with Sony", but that isn't the case for the > > imx219 datasheet. I take that as it is permitted within the defined > > ranges. > > I'm not that much concerned of vertical blanking, changing that within the > valid range has effects on the image itself very seldom. Horizontal > blanking is different though and this is what the patch makes changeable, > including a change in the default value. Of course there are big > differences between sensors here. The intention was that the default value shouldn't change, and as the overall PIXELS_PER_LINE value was meant to be retained on a mode change the value used should only change if an application changes V4L2_CID_HBLANK. If I blundered in the implementation of that, then that should be fixed (I know Jacopo made comments, but I haven't had a chance to investigate). I doubt we'd get validation from Sony beyond the contents of the datasheet. Potentially as the sensor is so old they don't have the information or engineers involved. I'm happy to set up a test system and capture a set of images with HBLANK from min to max at some increment. With the same exposure and gain they should all be identical as long as there isn't any movement (rolling shutter with longer readout times and all that). Would that be satisfactory? For contrast, the IMX290 datasheet states that VMAX shall be fixed at 0x465 for all-pixel mode / 0x2ee for 720p mode, and HMAX should be changed for frame rate control. As you say, sensors differ. Dave > -- > Kind regards, > > Sakari Ailus
