diff --git a/src/cap_pool.h b/src/cap_pool.h
index a1bf6a5..3aba400 100644
--- a/src/cap_pool.h
+++ b/src/cap_pool.h
@@ -67,7 +67,15 @@
 
 #include <linux/videodev2.h>	/* for VIDEO_MAX_PLANES */
 
-#define MIN_CAP_POOL 24
+/*
+ * iter17 α-20: reduced from 24 to 11 as a test — matches kdirect
+ * (ffmpeg-v4l2request) CAPTURE pool depth on the same fixture. iter15
+ * ioctl-sequence diff showed kdirect issues CREATE_BUFS count=1 × 11
+ * while libva did CREATE_BUFS count=24. If pool depth or buffer-index
+ * range affects rkvdec's per-codec state machine, this is a discriminator.
+ * Revert to 24 if 11 is too tight for mpv-16-surface continuous playback.
+ */
+#define MIN_CAP_POOL 11
 
 enum cap_slot_state {
 	CAP_SLOT_FREE = 0,	/* available for a new decode acquisition */