tests: fix benchmark (yuv420p fixture, identity probe frame counter)

tests/benchmark_decode.py

@@ -77,7 +77,7 @@ def _generate_test_video(path: str, Gst, GLib) -> None:
     print(f"  (duration={GENERATE_DURATION}s, size=1920x1080, rate={GENERATE_FPS}/1)")
     pipe_str = (
         f"videotestsrc num-buffers={GENERATE_DURATION * GENERATE_FPS} "
-        f"! video/x-raw,width=1920,height=1080,framerate={GENERATE_FPS}/1 "
+        f"! video/x-raw,width=1920,height=1080,framerate={GENERATE_FPS}/1,format=I420 "
         f"! avenc_h264 bitrate=4000000 "
         f"! h264parse ! mp4mux ! filesink location={path}"
     )
@@ -151,6 +151,16 @@ def _run_benchmark(
         sink.set_property("max-buffers", 4)
         sink.set_property("drop", False)
         sink.connect("new-sample", on_new_sample)
+    else:
+        # fakesink path: count frames via identity handoff signal
+        probe = pipeline.get_by_name("probe")
+        if probe:
+            def on_handoff(elem, buf, pad):
+                n = frame_count[0]
+                frame_count[0] = n + 1
+                if n >= WARMUP_FRAMES:
+                    frame_times.append(time.monotonic())
+            probe.connect("handoff", on_handoff)
 
     loop = GLib.MainLoop()
 
@@ -180,7 +190,7 @@ def _run_benchmark(
     wall = t_wall_end - t_wall_start
     cpu_pct = _cpu_percent(*cpu_before, *cpu_after)
 
-    if is_appsink and len(frame_times) >= 2:
+    if len(frame_times) >= 2:
         measure_frames = len(frame_times)
         measure_wall = frame_times[-1] - frame_times[0]
         fps = (measure_frames - 1) / measure_wall if measure_wall > 0 else 0
@@ -243,7 +253,8 @@ def main() -> None:
     # 1. SW fakesink — pure decode throughput
     if av_ok:
         _set_mpp_rank(GST_RANK_NONE)  # ensure avdec_h264 wins
-        pipe = f"filesrc location={video_path} ! decodebin ! fakesink sync=false"
+        pipe = (f"filesrc location={video_path} ! decodebin "
+                f"! identity name=probe signal-handoffs=true ! fakesink sync=false")
         results.append(_run_benchmark(
             "SW fakesink (avdec_h264 → discard)",
             video_path, pipe, is_appsink=False, Gst=Gst, GLib=GLib,
@@ -265,7 +276,8 @@ def main() -> None:
     # 3. HW fakesink — pure MPP decode throughput
     if mpp_ok:
         _set_mpp_rank(MPP_RANK_HIGH)  # prefer mppvideodec
-        pipe = f"filesrc location={video_path} ! decodebin ! fakesink sync=false"
+        pipe = (f"filesrc location={video_path} ! decodebin "
+                f"! identity name=probe signal-handoffs=true ! fakesink sync=false")
         results.append(_run_benchmark(
             "HW fakesink (mppvideodec → discard)",
             video_path, pipe, is_appsink=False, Gst=Gst, GLib=GLib,