Hi everybody, the VIDIOC_[GS]_JPEGCOMP documentation in the V4L2 specification is far from being clear and complete (which is probably why it's marked as [to do]). I'm implementing support for this ioctl in the uvcvideo driver and I'd like to request your opinion about the expected ioctl behavior. - VIDIOC_[GS]_JPEGCOMP only make sense for (M)JPEG compressed formats. Should the ioctls return an error (-EINVAL ?) when the currently selected format isn't (M)JPEG ? - VIDIOC_S_JPEGCOMP is a write-only ioctl. As such it can't return the quality value really applied to the device when the requested quality can't be achieved (either because the value is out of bounds or the quality values supported by the device have a higher granularity). Should the ioctl still succeed in that case, and apply a closest match quality to the device ? - Similarly, should VIDIOC_S_JPEGCOMP fail if the requested JPEG markers combination is not supported by the device, or should it silently fix the value ? - While JPEG-specific fields (such as markers) don't make sense for frame- based compressed formats other than (M)JPEG, the quality field does. Would it be abusing the ioctl to use the quality field to get/set the compression quality for compression formats similar to JPEG ? If it would, what's the preferred way to set compression quality in V4L2 ? Best regards, Laurent Pinchart -- 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
