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Switch to picamera2 and add timestamp overlay #485

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Jonathan-Woo Oct 23, 2025
8c4a52e
Update src/ac_training_lab/picam/device.py
Jonathan-Woo Oct 23, 2025
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178 changes: 72 additions & 106 deletions src/ac_training_lab/picam/device.py
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Original file line number Diff line number Diff line change
@@ -1,8 +1,12 @@
import json
import subprocess
import shutil
import logging
import socket
import time
from multiprocessing import Process

import cv2
import requests
from libcamera import Transform
from my_secrets import (
CAM_NAME,
CAMERA_HFLIP,
Expand All @@ -11,107 +15,58 @@
PRIVACY_STATUS,
WORKFLOW_NAME,
)


def get_camera_command():
"""
Returns the available camera command: 'rpicam-vid' (trixie) or 'libcamera-vid' (bookworm).
"""
if shutil.which("rpicam-vid"):
return "rpicam-vid"
elif shutil.which("libcamera-vid"):
return "libcamera-vid"
else:
raise RuntimeError(
"Neither 'rpicam-vid' nor 'libcamera-vid' command found on this system"
)
from picamera2 import MappedArray, Picamera2, Preview
from picamera2.encoders import H264Encoder
from picamera2.outputs import FfmpegOutput


def start_stream(ffmpeg_url):
"""
Starts the libcamera -> ffmpeg pipeline and returns two Popen objects:
p1: camera process (rpicam-vid or libcamera-vid)
p2: ffmpeg process
"""
# Get the available camera command
camera_cmd = get_camera_command()

# First: camera command with core parameters
libcamera_cmd = [
camera_cmd,
"--inline",
"--nopreview",
"-t",
"0",
"--mode",
"1536:864", # A known 16:9 sensor mode
"--width",
"854", # Scale width
"--height",
"480", # Scale height
"--framerate",
"15", # Frame rate
"--codec",
"h264", # H.264 encoding
"--bitrate",
"1000000", # ~1 Mbps video
]

# Add flip parameters if needed
if CAMERA_VFLIP:
libcamera_cmd.extend(["--vflip"])
if CAMERA_HFLIP:
libcamera_cmd.extend(["--hflip"])
picam2 = Picamera2()

# Add output parameters last
libcamera_cmd.extend(["-o", "-"]) # Output to stdout (pipe)
picam2.configure(
picam2.create_video_configuration(
main={"size": (1280, 720)}, transform=Transform(hflip=CAMERA_HFLIP, vflip=CAMERA_VFLIP)
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Copilot AI Oct 23, 2025

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The video resolution changed from 854x480 to 1280x720 without corresponding bitrate adjustment. This represents a 2.5x increase in pixels but uses the same 1 Mbps bitrate (line 65), which may result in lower quality video. Consider increasing the bitrate to 2-3 Mbps for 720p streaming.

Copilot uses AI. Check for mistakes.
)
)

# Second: ffmpeg command
# Configure timestamp
bg_colour = (0, 0, 0)
colour = (255, 255, 255)
origin = (0, 30)
font = cv2.FONT_HERSHEY_SIMPLEX
scale = 1
thickness = 2
# Precompute text size for timestamp format (fixed width)
sample_timestamp = "2024-06-01 12:34:56" # Matches "%Y-%m-%d %X"
text_size, _ = cv2.getTextSize(sample_timestamp, font, scale, thickness)
text_w, text_h = text_size

def apply_timestamp(request):
timestamp = time.strftime("%Y-%m-%d %X")
with MappedArray(request, "main") as m:
x, y = origin
cv2.rectangle(m.array, (0, 0), (x + text_w, y + text_h), bg_colour, -1)
cv2.putText(m.array, timestamp, origin, font, scale, colour, thickness)
# Create the ffmpeg command for streaming
ffmpeg_cmd = [
"ffmpeg",
# Generate silent audio source
"-f",
"lavfi",
"-i",
"anullsrc=channel_layout=stereo:sample_rate=44100",
# Handle timestamps/threading
"-thread_queue_size",
"1024",
"-use_wallclock_as_timestamps",
"1",
# Read H.264 video from pipe
"-i",
"pipe:0",
# Copy the H.264 video directly
"-c:v",
"copy",
# Encode audio as AAC
"-c:a",
"aac",
"-b:a",
"128k",
"-preset",
"fast",
"-strict",
"experimental",
# Output format is FLV, then final RTMP URL
# Most options such as wallclock_for_timestamps, thread_queue_size, and audio are handled by Picamera2 https://github.com/raspberrypi/picamera2/blob/main/picamera2/outputs/ffmpegoutput.py
# FLV is the livestream output file format
"-f",
"flv",
ffmpeg_url,
]

# Start camera process, capturing its output in a pipe
p1 = subprocess.Popen(
libcamera_cmd, stdout=subprocess.PIPE, stderr=subprocess.STDOUT
)
ffmpeg_cmd = " ".join(ffmpeg_cmd)

# Start ffmpeg, reading from p1's stdout
p2 = subprocess.Popen(ffmpeg_cmd, stdin=p1.stdout, stderr=subprocess.STDOUT)
# Initialize FfmpegOutput to handle streaming
# Audio is required for youtube streaming. Since the rpi and rpi cameras don't have mics, the audio signal is blank
ffmpeg_output = FfmpegOutput(ffmpeg_cmd, audio=True)
YOUTUBE_720P_BITRATE = 1000000
h264_encoder = H264Encoder(bitrate=YOUTUBE_720P_BITRATE)

# Close p1's stdout in the parent process
p1.stdout.close()
picam2.start_recording(encoder=h264_encoder, output=ffmpeg_output)

return p1, p2
return picam2


def call_lambda(action, CAM_NAME, WORKFLOW_NAME, privacy_status="private"):
Expand Down Expand Up @@ -165,24 +120,35 @@ def call_lambda(action, CAM_NAME, WORKFLOW_NAME, privacy_status="private"):

print(f"Streaming to: {ffmpeg_url}")

while True:
print("Starting stream..")
p1, p2 = start_stream(ffmpeg_url)
print("Stream started")
interrupted = False
# Gracefully terminate picamera2 on keyboard interrupt or on error.
# Reattempt if terminated due to error.
run = True
while run:
picam2 = None
try:
p2.wait()
print("Starting stream...")
picam2 = start_stream(ffmpeg_url)
print("Stream started")

# Spin and wait for error.
while True:
time.sleep(1)

except KeyboardInterrupt:
print("Received interrupt signal, exiting...")
interrupted = True
print("Keyboard Interrupt")
run = False

except Exception as e:
print(e)
print(f"Stream crashed {e}")
finally:
print("Terminating processes..")
p1.terminate()
p2.terminate()
print("Processes terminated.")
if interrupted:
break
else:
print("Retrying..")
if picam2:
try:
print("Stopping stream")
picam2.stop_recording()
print("Stream stopped")
except Exception as e:
print(f"Error stopping stream {e}")

if run:
print("Retrying in 3 seconds")
time.sleep(3)
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