jetson pyav update
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Jetson Orin Nano
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#!/usr/bin/env python3
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"""
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USB camera format and FPS tester for Jetson.
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- Lists available formats/resolutions via v4l2-ctl.
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- For selected modes, opens the camera with OpenCV and measures per-frame
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capture time (ms) to show real delivered FPS/latency.
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"""
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import argparse
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import subprocess
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import sys
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import time
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import statistics
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from typing import List, Tuple
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import cv2
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def run_v4l2_list_formats(device: str) -> str:
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"""Return the raw output of v4l2-ctl --list-formats-ext."""
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try:
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out = subprocess.check_output(
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["v4l2-ctl", f"--device={device}", "--list-formats-ext"],
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stderr=subprocess.STDOUT,
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text=True,
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)
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return out
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except (subprocess.CalledProcessError, FileNotFoundError) as e:
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print(f"[WARN] Failed to run v4l2-ctl: {e}")
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return ""
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def parse_formats(output: str) -> List[Tuple[str, int, int, List[float]]]:
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"""
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Parse v4l2-ctl --list-formats-ext output.
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Returns list of (fourcc, width, height, fps_list).
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"""
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lines = output.splitlines()
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formats: List[Tuple[str, int, int, List[float]]] = []
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current_fourcc = None
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for line in lines:
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line = line.strip()
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if line.startswith("[") and "):" in line and "'" in line:
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# Example: [0]: 'MJPG' (Motion-JPEG, compressed)
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try:
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fourcc = line.split("'")[1]
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current_fourcc = fourcc
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except Exception:
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current_fourcc = None
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elif line.startswith("Size: Discrete") and current_fourcc:
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# Example: Size: Discrete 1280x720
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try:
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parts = line.split()
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wh = parts[-1]
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w_str, h_str = wh.split("x")
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width = int(w_str)
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height = int(h_str)
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formats.append((current_fourcc, width, height, []))
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except Exception:
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pass
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elif "Interval:" in line and "fps" in line and formats:
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# Example: Interval: Discrete 0.033s (30.000 fps)
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try:
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fps_part = line.split("(")[-1].split("fps")[0]
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fps = float(fps_part)
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fourcc, w, h, fps_list = formats[-1]
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fps_list.append(fps)
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formats[-1] = (fourcc, w, h, fps_list)
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except Exception:
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pass
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return formats
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def fourcc_to_int(code: str) -> int:
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return cv2.VideoWriter_fourcc(*code)
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def benchmark_mode(
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device_index: int,
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fourcc: str,
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width: int,
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height: int,
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target_fps: float,
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warmup: int = 10,
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measure_frames: int = 60,
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) -> None:
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"""Open a specific mode and measure per-frame capture time."""
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print(f"\n=== Testing {fourcc} {width}x{height} @ {target_fps:.1f} fps ===")
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cap = cv2.VideoCapture(device_index, cv2.CAP_V4L2)
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if not cap.isOpened():
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print(" [ERROR] Failed to open device with V4L2 backend.")
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return
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cap.set(cv2.CAP_PROP_FOURCC, fourcc_to_int(fourcc))
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cap.set(cv2.CAP_PROP_FRAME_WIDTH, width)
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cap.set(cv2.CAP_PROP_FRAME_HEIGHT, height)
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cap.set(cv2.CAP_PROP_FPS, target_fps)
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# Query negotiated parameters
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negotiated_w = int(cap.get(cv2.CAP_PROP_FRAME_WIDTH))
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negotiated_h = int(cap.get(cv2.CAP_PROP_FRAME_HEIGHT))
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negotiated_fps = cap.get(cv2.CAP_PROP_FPS)
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negotiated_fourcc_val = int(cap.get(cv2.CAP_PROP_FOURCC))
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negotiated_fourcc = "".join(
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chr((negotiated_fourcc_val >> 8 * i) & 0xFF) for i in range(4)
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)
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print(
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f" Negotiated: {negotiated_w}x{negotiated_h} {negotiated_fourcc} "
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f"@ {negotiated_fps:.1f} fps (backend={cap.getBackendName()})"
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)
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# Warm-up frames (to let auto-exposure, buffers, etc. settle)
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for i in range(warmup):
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ret, _ = cap.read()
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if not ret:
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print(f" [WARN] Warmup frame {i} failed.")
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time.sleep(0.05)
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times_ms: List[float] = []
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for i in range(measure_frames):
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t0 = time.perf_counter()
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ret, _ = cap.read()
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t1 = time.perf_counter()
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if not ret:
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print(f" [WARN] Capture failed at frame {i}.")
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break
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times_ms.append((t1 - t0) * 1000.0)
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cap.release()
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if not times_ms:
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print(" [ERROR] No successful frames captured.")
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return
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mean_ms = statistics.mean(times_ms)
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med_ms = statistics.median(times_ms)
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min_ms = min(times_ms)
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max_ms = max(times_ms)
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eff_fps = 1000.0 / mean_ms
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print(
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f" Frames measured: {len(times_ms)}\n"
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f" Capture time (ms): mean={mean_ms:.2f}, median={med_ms:.2f}, "
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f"min={min_ms:.2f}, max={max_ms:.2f}\n"
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f" Effective FPS from capture timing: {eff_fps:.2f}"
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)
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def main() -> None:
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parser = argparse.ArgumentParser(
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description="List USB camera formats and benchmark capture times."
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)
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parser.add_argument(
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"--device",
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default="/dev/video4",
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help="V4L2 device path (default: /dev/video0)",
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)
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parser.add_argument(
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"--index",
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type=int,
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default=0,
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help="OpenCV device index (default: 0)",
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)
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parser.add_argument(
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"--test-modes",
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nargs="*",
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default=["MJPG:640x480:30", "MJPG:1280x720:30"],
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help=(
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"Modes to benchmark as FOURCC:WxH:FPS. "
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"Example: MJPG:640x480:30 YUYV:640x480:30"
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),
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)
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args = parser.parse_args()
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print(f"== v4l2-ctl formats for {args.device} ==")
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raw = run_v4l2_list_formats(args.device)
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if not raw:
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print("No v4l2-ctl output; skipping format list.")
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else:
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print(raw)
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parsed = parse_formats(raw)
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if parsed:
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print("\n== Parsed formats (FOURCC WxH [fps...]) ==")
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for fourcc, w, h, fps_list in parsed:
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fps_str = ", ".join(f"{f:.1f}" for f in fps_list) if fps_list else "?"
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print(f" {fourcc} {w}x{h} [{fps_str}]")
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print("\n== Benchmarking capture time with OpenCV ==")
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for mode_str in args.test_modes:
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try:
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fourcc_s, wh_s, fps_s = mode_str.split(":")
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w_s, h_s = wh_s.lower().split("x")
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w = int(w_s)
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h = int(h_s)
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fps = float(fps_s)
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except ValueError:
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print(f"[WARN] Cannot parse test mode '{mode_str}', expected FOURCC:WxH:FPS")
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continue
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benchmark_mode(args.index, fourcc_s, w, h, fps)
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if __name__ == "__main__":
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try:
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main()
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except KeyboardInterrupt:
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print("\nInterrupted by user.", file=sys.stderr)
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