Video Fundamentals: Frame Rates, Codecs, Formats & Streaming

Core Concepts of Video Fundamentals

Video is a sequence of frames (still images) displayed at a rapid rate to create the illusion of motion. Understanding its technical foundations—frame rate, resolution, color depth, compression, and formats—is essential for designing, optimizing, and streaming multimedia content.

1. Video Frame Structure and Frame Rate

How Video Works

Video is created by capturing or generating a series of frames per second (fps). The human eye perceives motion when frames are displayed at a rate of at least 16 fps, but standard video uses:

• 24 fps (cinematic, film-like smoothness, used in movies)
• 30 fps (NTSC standard, common in TV broadcasts)
• 60 fps (smooth motion, used in sports, gaming, and high-end streaming)

Worked Example: Frame Rate in eSewa’s Video Verification

When users upload a video for eSewa’s KYC (Know Your Customer) verification, the system checks:

• Minimum 30 fps (to ensure smooth face movement detection).
• Resolution ≥ 720p (to avoid pixelation in facial recognition).
• Duration ≥ 5 seconds (to capture full face rotation).

If the video is below 24 fps, the system rejects it with an error:

"Video too slow. Upload at least 30 frames per second for verification."

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2. Video Resolution and Aspect Ratio

Resolution defines the number of pixels in a frame (width × height). Common resolutions:

Real-World Example: YouTube’s Adaptive Bitrate Streaming

YouTube adjusts resolution and frame rate based on:

• User’s internet speed (e.g., 480p for slow connections, 1080p for fast).
• Device capability (mobile vs. desktop).
• Content type (e.g., gaming streams use 60 fps, while documentaries use 24 fps).

Why?

• Lower resolution = smaller file size = faster loading.
• Higher fps = smoother motion but larger file size.

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3. Color Depth and Bit Depth

Color depth determines how many colors a pixel can display, measured in bits per pixel (bpp):

• 8 bpp (256 colors) → Used in old GIFs, low-quality videos.
• 24 bpp (16.7 million colors) → Standard for HD videos (RGB: 8 bits per channel).
• 32 bpp (4.3 billion colors) → Used in high-end video (includes alpha channel for transparency).

Example: Pathao’s Driver App UI Pathao’s app uses 24-bit color for:

• Smooth gradients in the map background.
• Clear text on buttons (e.g., "Start Ride").
• Accurate color representation in driver profiles (e.g., vehicle colors).

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4. Video Compression Techniques

Uncompressed video files are extremely large (e.g., 1 minute of 1080p video = ~1 GB). Compression reduces file size while maintaining quality.

Lossless vs. Lossy Compression

Key Compression Standards

Example: Daraz’s Product Videos Daraz compresses product videos using:

• H.264 (AVC) for fast loading on mobile.
• Adaptive bitrate streaming to switch between 720p and 1080p based on user speed.

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5. Video File Formats

Video files are stored in containers that hold:

• Video data (compressed frames)
• Audio data (separate or embedded)
• Metadata (timestamps, subtitles)

Example: NTC’s Broadcast Standards Nepal Television (NTC) uses:

• MP4 (H.264) for online streaming (smaller file size).
• MPEG-TS for live TV broadcasts (real-time transmission).

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6. Video Streaming Protocols

Streaming delivers video without full download using:

1. Progressive Download → User downloads while playing (e.g., YouTube).
2. Adaptive Bitrate Streaming (ABR) → Adjusts quality in real-time (e.g., Netflix).
3. Live Streaming → Low-latency transmission (e.g., Facebook Live).

Example: NEPSE’s Live Stock Market Streaming NEPSE uses HLS (HTTP Live Streaming) to:

• Broadcast real-time stock prices with minimal delay.
• Support mobile users (iOS/Android).
• Auto-adjust quality based on network speed.

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In the Real World

1. eSewa’s Video KYC

   • Uses 30+ fps, 720p minimum for facial recognition.
   • Rejects low-frame-rate videos to prevent spoofing.

2. Pathao’s Driver App

   • 24-bit color depth ensures clear UI for navigation.
   • H.264 compression reduces video call file sizes.

3. YouTube’s Adaptive Streaming

   • Switches between 360p (slow networks) and 4K (fast networks).
   • Uses VP9 codec for efficiency in WebM format.

4. NTC’s Digital Broadcast

   • MPEG-TS for live TV (low latency).
   • MP4 (H.264) for on-demand content.

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Exam Tip

1. Memorize key standards:

   • Frame rates: 24 (film), 30 (NTSC), 60 (gaming).
   • Resolutions: 720p (HD), 1080p (Full HD), 4K (UHD).
   • Codecs: H.264 (most common), H.265 (4K), VP9 (YouTube).

2. Compare compression types:

   • Lossless = No quality loss (used in archives).
   • Lossy = Smaller files (used in streaming).

3. Relate to real-world apps:

   • eSewa → Frame rate for KYC.
   • YouTube → Adaptive bitrate streaming.
   • NTC → MPEG-TS for live broadcasts.

4. Diagram-based questions:

   • Draw a frame rate vs. file size graph.
   • Show a video streaming protocol flowchart (HLS vs. DASH).

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Visual Summaries