Hi, I am working on interlaced capture devices. There is some confusion in handling height parameter between application and driver. Capture device is able to produce 1920x1080i, where one field (top/bottom) resolution is 1920x540. Query 1: What should be the height passed by application to driver to capture 1920x1080i resolution? According to v4l2 specification: https://www.kernel.org/doc/html/v4.16/media/uapi/v4l/pixfmt-v4l2.html Image height in pixels. If field is one of V4L2_FIELD_TOP, V4L2_FIELD_BOTTOM or V4L2_FIELD_ALTERNATE then height refers to the number of lines in the field, otherwise it refers to the number of lines in the frame (which is twice the field height for interlaced formats). Query 2: I can think of 4 possible cases here: i) If application calling VIDIOC_TRY_FMT with filed as V4L2_FIELD_ALTERNATE and capture hardware supports same ii) If application calling VIDIOC_TRY_FMT with filed as V4L2_FIELD_NONE and capture hardware supports same iii) If application calling VIDIOC_TRY_FMT with field as V4L2_FIELD_NONE (progressive) and capture hardware supports V4L2_FIELD_ALTERNATE iv) If application calling VIDIOC_TRY_FMT with field as V4L2_FIELD_ALTERNATE (progressive) and capture hardware supports V4L2_FIELD_NONE The first 2 cases are straightforward. What should be the driver behavior for iii and iv ? Should it alter height passed by the application accordingly? I see some of the capture drivers are dividing height by 2 if field is V4L2_FIELD_ALTERNATE. Is this the right behavior? Regards, Satish
