Gemini Video Understanding Skill#

Purpose#

This skill enables video analysis and object counting using the Google Gemini API, with a focus on counting pedestrians, detecting objects, tracking movement, and analyzing surveillance footage. It supports precise prompting for differentiated counting (e.g., pedestrians vs cyclists vs vehicles).

When to Use#

• Counting pedestrians, vehicles, or other objects in surveillance videos
• Distinguishing between different types of objects (walkers vs cyclists, cars vs trucks)
• Analyzing traffic patterns and movement through a scene
• Processing multiple videos for batch object counting
• Extracting structured count data from video footage

Required Libraries#

The following Python libraries are required:

python

from google import genai
from google.genai import types
import os
import time

Input Requirements#

• File formats: MP4, MPEG, MOV, AVI, FLV, MPG, WebM, WMV, 3GPP

• Size constraints:

  • Use inline bytes for small files (rule of thumb: <20MB).
  • Use the File API upload flow for larger videos (most surveillance footage).
  • Always wait for processing to complete before analysis.

• Video quality: Higher resolution provides better counting accuracy for distant objects

• Duration: Longer videos may require longer processing times; consider the full video length for accurate counting

Output Schema#

For object counting tasks, structure results as JSON:

json

{
  "success": true,
  "video_file": "surveillance_001.mp4",
  "model": "gemini-2.0-flash-exp",
  "counts": {
    "pedestrians": 12,
    "cyclists": 3,
    "vehicles": 5
  },
  "notes": "Optional observations about the counting process or edge cases"
}

Field Descriptions#

• success: Whether the analysis completed successfully
• video_file: Name of the analyzed video file
• model: Gemini model used for the request
• counts: Object counts by category
• notes: Any clarifications or warnings about the count

Code Examples#

Basic Pedestrian Counting (File API Upload)#

python

from google import genai
import os
import time
import re

client = genai.Client(api_key=os.getenv("GEMINI_API_KEY"))

# Upload video (File API for >20MB)
myfile = client.files.upload(file="surveillance.mp4")

# Wait for processing
while myfile.state.name == "PROCESSING":
    time.sleep(5)
    myfile = client.files.get(name=myfile.name)

if myfile.state.name == "FAILED":
    raise ValueError("Video processing failed")

# Prompt for counting pedestrians with clear exclusion criteria
prompt = """Count the total number of pedestrians who are WALKING through the scene in this surveillance video.

IMPORTANT RULES:
- ONLY count people who are walking on foot
- DO NOT count people riding bicycles
- DO NOT count people driving cars or other vehicles
- Count each unique pedestrian only once, even if they appear in multiple frames

Provide your answer as a single integer number representing the total count of pedestrians.
Answer with just the number, nothing else.
Your answer should be enclosed in <answer> and </answer> tags, such as <answer>5</answer>.
"""

response = client.models.generate_content(
    model="gemini-2.0-flash-exp",
    contents=[prompt, myfile],
)

# Parse the response
response_text = response.text.strip()
match = re.search(r"<answer>(\d+)</answer>", response_text)
if match:
    count = int(match.group(1))
    print(f"Pedestrian count: {count}")
else:
    print("Could not parse count from response")

Batch Processing Multiple Videos#

python

from google import genai
import os
import time
import re

def upload_and_wait(client, file_path: str, max_wait_s: int = 300):
    """Upload video and wait for processing."""
    myfile = client.files.upload(file=file_path)
    waited = 0

    while myfile.state.name == "PROCESSING" and waited < max_wait_s:
        time.sleep(5)
        waited += 5
        myfile = client.files.get(name=myfile.name)

    if myfile.state.name == "FAILED":
        raise ValueError(f"Video processing failed: {myfile.state.name}")
    if myfile.state.name == "PROCESSING":
        raise TimeoutError(f"Processing timeout after {max_wait_s}s")

    return myfile

client = genai.Client(api_key=os.getenv("GEMINI_API_KEY"))

# Process all videos in directory
video_dir = "/app/video"
video_extensions = {".mp4", ".mkv", ".avi", ".mov"}
results = {}

for filename in os.listdir(video_dir):
    if any(filename.lower().endswith(ext) for ext in video_extensions):
        video_path = os.path.join(video_dir, filename)

        print(f"Processing {filename}...")

        # Upload and analyze
        myfile = upload_and_wait(client, video_path)

        response = client.models.generate_content(
            model="gemini-2.0-flash-exp",
            contents=["Count pedestrians walking through the scene. Answer with just the number.", myfile],
        )

        # Extract count
        count = int(re.search(r'\d+', response.text).group())
        results[filename] = count
        print(f"  Count: {count}")

print(f"\nProcessed {len(results)} videos")
# Results dictionary can now be used for further processing or saving

Differentiating Object Types#

python

# Count different categories separately
prompt = """Analyze this surveillance video and count:
1. Pedestrians (people walking on foot)
2. Cyclists (people riding bicycles)
3. Vehicles (cars, trucks, motorcycles)

RULES:
- Count each unique individual/vehicle only once
- If someone switches from walking to cycling, count them in their primary mode
- Provide counts as three separate numbers

Format your answer as:
Pedestrians: <number>
Cyclists: <number>
Vehicles: <number>
"""

response = client.models.generate_content(
    model="gemini-2.0-flash-exp",
    contents=[prompt, myfile],
)

# Parse multiple counts
text = response.text
pedestrians = int(re.search(r'Pedestrians:\s*(\d+)', text).group(1))
cyclists = int(re.search(r'Cyclists:\s*(\d+)', text).group(1))
vehicles = int(re.search(r'Vehicles:\s*(\d+)', text).group(1))

Using Answer Tags for Reliable Parsing#

python

# Request structured output with XML-like tags
prompt = """Count the total number of pedestrians walking through the scene.

You should reason and think step by step. Provide your answer as a single integer.
Your answer should be enclosed in <answer> and </answer> tags, such as <answer>5</answer>.
"""

response = client.models.generate_content(
    model="gemini-2.0-flash-exp",
    contents=[prompt, myfile],
)

# Robust extraction
match = re.search(r"<answer>(\d+)</answer>", response.text)
if match:
    count = int(match.group(1))
else:
    # Fallback: try to find any number in response
    numbers = re.findall(r'\d+', response.text)
    count = int(numbers[0]) if numbers else 0

Best Practices#

• Use the File API for all surveillance videos (typically >20MB) and always wait for processing to complete.
• Be specific in prompts: Clearly define what to count and what to exclude (e.g., "walking pedestrians only, not cyclists").
• Use structured output formats: Request answers in specific formats (like <answer>N</answer>) for reliable parsing.
• Ask for reasoning: Include "think step by step" to improve counting accuracy.
• Handle edge cases: Specify rules for partial appearances, people entering/exiting frame, and mode changes.
• Use gemini-2.0-flash-exp or gemini-2.5-flash: These models provide good balance of speed and accuracy for object counting.
• Test with sample videos: Verify prompt effectiveness on representative samples before batch processing.

Error Handling#

python

import time

def upload_and_wait(client, file_path: str, max_wait_s: int = 300):
    """Upload video and wait for processing with timeout."""
    myfile = client.files.upload(file=file_path)
    waited = 0

    while myfile.state.name == "PROCESSING" and waited < max_wait_s:
        time.sleep(5)
        waited += 5
        myfile = client.files.get(name=myfile.name)

    if myfile.state.name == "FAILED":
        raise ValueError(f"Video processing failed: {myfile.state.name}")
    if myfile.state.name == "PROCESSING":
        raise TimeoutError(f"Processing timeout after {max_wait_s}s")

    return myfile

def count_with_fallback(client, video_path):
    """Count pedestrians with error handling and fallback."""
    try:
        myfile = upload_and_wait(client, video_path)

        prompt = """Count pedestrians walking through the scene.
        Answer with just the number in <answer></answer> tags."""

        response = client.models.generate_content(
            model="gemini-2.0-flash-exp",
            contents=[prompt, myfile],
        )

        # Try structured parsing first
        match = re.search(r"<answer>(\d+)</answer>", response.text)
        if match:
            return int(match.group(1))

        # Fallback to any number found
        numbers = re.findall(r'\d+', response.text)
        if numbers:
            return int(numbers[0])

        print(f"Warning: Could not parse count, defaulting to 0")
        return 0

    except Exception as e:
        print(f"Error processing video: {e}")
        return 0

Common issues:

• Upload processing stuck: Use timeout logic and fail gracefully after max wait time
• Ambiguous responses: Use structured output tags like <answer></answer> for reliable parsing
• Rate limits: Add retry logic with exponential backoff for batch processing
• Inconsistent counts: Be very explicit in prompts about counting rules and exclusions

Limitations#

• Counting accuracy depends on video quality, camera angle, and object size/distance
• Very crowded scenes may have higher counting variance
• Occlusion (objects blocking each other) can affect accuracy
• Long videos require longer processing times (typically 5-30 seconds per video)
• The model may occasionally misclassify similar objects (e.g., motorcyclist as cyclist)
• For highest accuracy, use clear prompts with explicit inclusion/exclusion criteria

Version History#

• 1.0.0 (2026-01-21): Tailored for pedestrian traffic counting with focus on object counting, differentiation, and batch processing

Resources#

• Video API Docs
• Get API Key
• Pricing
• Python SDK Documentation