diff --git a/src/v4l2.c b/src/v4l2.c
index 5267072..d881cbe 100644
--- a/src/v4l2.c
+++ b/src/v4l2.c
@@ -447,12 +447,42 @@ static int v4l2_ioctl_controls(int video_fd, int request_fd, unsigned long ioc,
 
 	rc = ioctl(video_fd, ioc, &controls);
 	if (rc < 0 && errno == EINVAL && ioc == VIDIOC_S_EXT_CTRLS) {
-		request_log("S_EXT_CTRLS EINVAL: num_controls=%u error_idx=%u\n",
+		int saved_errno = errno;
+		request_log("S_EXT_CTRLS EINVAL: num_controls=%u error_idx=%u (count = obfuscated)\n",
 			    num_controls, controls.error_idx);
 		for (unsigned int i = 0; i < num_controls; i++) {
 			request_log("  ctrl[%u]: id=0x%08x size=%u\n",
 				    i, control_array[i].id, control_array[i].size);
 		}
+		/*
+		 * Retry with VIDIOC_TRY_EXT_CTRLS — kernel comment in
+		 * v4l2-ctrls-api.c:222-224 says TRY_EXT_CTRLS "never modifies
+		 * controls [so] error_idx is just set to whatever control has
+		 * an invalid value." Unlike S_EXT_CTRLS which deliberately
+		 * obfuscates by setting error_idx = count.
+		 */
+		struct v4l2_ext_controls try_controls;
+		memset(&try_controls, 0, sizeof(try_controls));
+		try_controls.controls = control_array;
+		try_controls.count = num_controls;
+		if (request_fd >= 0) {
+			try_controls.which = V4L2_CTRL_WHICH_REQUEST_VAL;
+			try_controls.request_fd = request_fd;
+		}
+		int try_rc = ioctl(video_fd, VIDIOC_TRY_EXT_CTRLS, &try_controls);
+		if (try_rc < 0) {
+			request_log("  TRY_EXT_CTRLS retry: errno=%d (%s) error_idx=%u\n",
+				    errno, strerror(errno), try_controls.error_idx);
+			if (try_controls.error_idx < num_controls) {
+				request_log("  --> failing control is ctrl[%u]: id=0x%08x size=%u\n",
+					    try_controls.error_idx,
+					    control_array[try_controls.error_idx].id,
+					    control_array[try_controls.error_idx].size);
+			}
+		} else {
+			request_log("  TRY_EXT_CTRLS retry: passed (S vs TRY semantics differ — likely cluster commit)\n");
+		}
+		errno = saved_errno;
 	}
 	return rc;
 }