In today’s digital era, where “Content is King,” online video streaming has become an integral part of our lives. In fact, an average viewer spends 17 hours a week consuming video content. So whether it’s watching movies, live events, or educational content, your users expect seamless and high-quality video experiences. You need infrastructure that can handle the delivery of video content on a global scale and with concurrent users. This is where a Video CDN – a specialized form of a CDN (Content Delivery Network) – is useful.

A Video CDN is a distributed system of servers strategically placed worldwide to reduce the load on your main (or origin) server. They cache, store, and deliver video content, reducing the effective distance between the actual source and the viewer. As a result, buffering and latency issues are minimized, leading to smoother and uninterrupted video playback.

But that’s only a simplified explanation. In this blog post, we will explore Video CDNs in detail, see how they work, and why you should use one for your online video streaming needs. Whether you are a content creator, an e-commerce platform, a video-on-demand service, or a video-based educational platform, understanding the inner workings of a Video CDN is essential to delivering high-quality video experiences that captivate and engage your audience.

So, let’s dive in!

What is a Video Content Delivery Network?

A Content Delivery Network (CDN) is a network of servers strategically distributed across multiple locations worldwide. The primary purpose of a CDN is to cache and deliver static content, such as HTML, CSS, images, and JavaScript, to users over the Internet. By storing copies of this content in multiple server locations and serving them from the server closest to the requesting user, CDNs aim to reduce latency and improve the overall performance of websites and applications.

While a regular CDN is designed to handle various types of content, a Video CDN takes the concept a step further by optimizing specifically for video content, whether live streams or VODs. Unlike static web pages or images, serving videos needs low latency, as short a buffering time as possible, and uninterrupted playback. To meet these demands, video CDNs incorporate specialized features and optimizations tailored to the unique requirements of streaming video.

Comparing Regular CDNs and Video CDNs

	REGULAR CDNS	VIDEO CDNS
Content type	Regular CDNs cache and deliver a wide variety of static content – HTML/CSS/JavaScript/fonts, binary files like software patches, and frequently requested API responses.	Video CDNs are purpose-built to specifically cache and deliver video content. Videos can be live streams, or standalone files (Video On Demand)
Caching Strategy	Regular CDNs cache items that have longer cache lifetimes and don’t really change much. So a simple file-level cache is enough.	Video CDNs can cache discrete video files, but most often, they need to cache dynamic video content at a granular level. So segments/chunks of each video file are cached.
Security	Since regular CDNs focus on the efficient delivery of just web pages, images, JavaScript, etc. Security in regular CDNs can thus be limited to basic authentication/authorization, and IP-based whitelisting/blacklisting.	Video CDNs are specifically designed for delivering live streams and on-demand videos, and so, in addition to regular security features they can also integrate Digital Rights Management (DRM) and more granular access control – like restricting content based on user roles, geographic regions (because of media rights, etc), or subscription tiers – as needed.
Storage and Hardware	Regular CDNs are designed to handle increased web traffic by replicating content across multiple edge servers, and their storage needs are optimized for fast retrieval of discrete, static content.	Video CDNs need to store and deliver live video streams as well as discrete video files, and also process this video content before delivery. For this reason, they require both additional bandwidth/storage and far more compute resources (to handle concurrent video processing tasks) than regular CDNs.
Content-specific optimization	Regular CDNs can use optimization strategies that are suitable for the static content they handle – such as minification to remove whitespace and comments from HTML/CSS/JS, and compressing them using Gzip, Brotli, etc.	Video CDNs being purpose-built for video, support Video transcoding, adaptive bitrate streaming, and may also provide video-specific analytics like viewer engagement, playback quality, and audience demographics rather than just traffic metrics.

In summary, a video content delivery network is a specialized type of CDN that focuses on efficiently delivering streaming video content to viewers worldwide. By leveraging caching, advanced algorithms, and optimizations specific to video streaming, video CDNs enable content providers to deliver high-quality videos with reduced latency, minimal buffering, and an overall enhanced streaming experience for their audience.

Why Use a Video CDN?

When it comes to online video streaming, leveraging a Video CDN offers numerous advantages that enhance the overall streaming experience for both content providers and viewers.

What are these benefits?

1. Minimized Latency: A Video CDN reduces latency by employing edge servers strategically positioned closer to viewers. The Video CDN ensures faster content delivery, reducing lag and a more seamless streaming experience by minimizing the distance between the content and the end users.
2. Reduced Buffering Time: With a Video CDN, buffering time is significantly decreased. By leveraging caching mechanisms and intelligent content delivery, the Video CDN pre-fetches and stores video segments closer to viewers. This enables smooth playback, eliminates buffering interruptions, and allows viewers to enjoy uninterrupted streaming.
3. Reduced Network Congestion: A Video CDN employs load balancing and distributed infrastructure, which helps alleviate network congestion. The Video CDN ensures efficient content delivery, even during peak demand periods by intelligently distributing traffic across multiple servers and utilizing edge computing. This reduces the strain on the network, resulting in a smoother streaming experience for all viewers.
4. Provides Encoding and Transcoding: Video CDNs include built-in encoding and transcoding capabilities, allowing content providers to optimize their videos for different devices and network conditions. By automatically converting videos into various formats and bitrates, the Video CDN ensures compatibility with a wide range of devices and network speeds and enabling content providers to save time and resources by offloading the encoding and transcoding tasks to the Video CDN.
5. Reduces Bandwidth Costs: A Video CDN optimizes bandwidth usage by implementing adaptive bitrate streaming. It dynamically adjusts the quality of the video stream based on the viewer’s available bandwidth, ensuring an uninterrupted playback experience while minimizing bandwidth consumption. This can lead to cost savings for content providers, especially when delivering content to a global audience.
6. Added Security: Video CDNs can provide secure delivery through features like DDoS mitigation, SSL/TLS encryption, access control, and content protection (DRM).

How Does a Video CDN Work?

To understand how a Video CDN operates, let’s break down the video streaming process into various steps, encompassing the “processing” required for videos to be ready for delivery and the actual “delivery” to viewers.

Processing – Encoding, Packaging, and Transcoding

Before videos can be streamed to viewers, they will undergo a series of steps – concurrently with the recording – to compress, optimize, and convert them to more suitable formats, striking a balance between file size and visual fidelity so they can be played back on a wide range of devices and network speeds.

1. Encoding: The first step in video streaming is video encoding, where the RAW source video being streamed is taken, compressed, and optimized into a standard digital format more suitable for streaming over the internet. Video from camera/capture devices can’t often be played back on most user devices, and so encoding involves compressing and converting the video using codecs like H.264, HEVC (H.265), and VP9 to a more suitable format, preserving an acceptable level of quality.
2. Transcoding: Transcoding is the process of creating multiple versions of the already encoded video, each at different resolutions, bitrates, or formats. Video transcoding is done to tailor videos for certain devices and network configurations. (For example: creating a 480p version of a video already encoded at 1080p because a target device isn’t powerful enough to handle full HD streaming.)
3. Packaging: Once the video is encoded/transcoded, it is divided into small segments known as “chunks.” These chunks typically span a (fixed) few seconds of video content. Packaging enables Adaptive Bitrate Streaming (ABR), creating manifests such as MPEG-DASH (Dynamic Adaptive Streaming over HTTP) or HLS (HTTP Live Streaming) to organize and structure these video chunks for streaming.

Delivery – A Distributed Architecture

The delivery process using a Video CDN (Content Delivery Network) involves hooking it up to the origin server, allowing it access to the encoded live stream (or VOD) along with its ABR manifests. Then, it distributes video content to users via a network of servers strategically placed globally.

1. Edge Servers with Segmented Caching: A Video CDN consists of a network of servers that are geographically distributed closer to the end-users – edge servers.
   
   Video CDNs reduce the load on the origin server by caching the encoded/transcoded video in chunks and distributing it across multiple such edge servers. When a request is made client-side for a stream, the CDN uses intelligent routing algorithms to determine the most optimal edge server to handle the user’s request (depending on network latency, server load, and proximity to the user).
2. Delivery of Cached Segments: Once an edge server is selected, the Video CDN checks if the requested video segments and manifests are available in its cache. If the content is absent, the edge server retrieves the required segments from the origin server, simultaneously caching them for future requests. The edge server then delivers the video content to the requesting client, and subsequent requests for the same stream can serve it from the cache instead of bothering the origin server.
3. Adaptive Bitrate Streaming: During playback, an ABR-compatible client-side video player continuously monitors the network conditions, including available bandwidth, latency, and packet loss, and dynamically adjusts its requested bitrate, requesting segments of that specific quality from the CDN, which then delivers it. This seamless switching between different quality levels ensures smooth playback and minimized buffering, and since the client-side video player doesn’t have to request the origin server for these chunks, ABR is even more efficient with a Video CDN in place.

Caching Live Streams vs. Caching Video-on-Demand

A Video CDN incorporates caching and delivery mechanisms to deliver live streams to viewers efficiently, but what about video-on-demand (VOD) scenarios? What’s the difference between how Video CDNs cache live streams vs. how they cache VODs?

For a live stream, the Video CDN caches segments in real-time, as they are recorded, encoded/transcoded/packaged, and broadcasted. This is a just-in-time (JIT) caching strategy using time-based Invalidation. To minimize latency and keep the viewing experience as close to ‘live’ as possible, this strategy focuses on caching only the most recent segments of the live video stream, dynamically invalidating and removing older segments that are no longer relevant or recent, rather than caching the stream in its entirety.

On the other hand, a Video on Demand (VOD) stream is streaming a discrete video file that resides in storage on the origin server. It is not a real-time stream. So the Video CDN can afford to employ a much simpler strategy for caching it – all it needs is access to a video file stored on the origin server, and it can cache it in its entirety, conventionally. All client requests for that particular VOD can now be served from the CDN edge servers, reducing the load on the origin server.

This is exactly why you should use a Video CDN in front of cloud storage like AWS S3 which stores your video content — to ensure the lowest costs and the highest uptime.

What to Look for When Choosing a Video CDN?

While there are several options out there, consider the following important factors to ensure your chosen Video CDN aligns with your requirements:

1. Coverage and Scalability: Does the Video CDN have a robust network of servers strategically located across various regions to deliver content efficiently to your target audience? Can it handle both spikes and reductions in viewer demand without compromising performance? This is critical for you to be able to accommodate sudden traffic spikes, maintain consistent video quality, and deliver a seamless experience to your viewers – all without breaking the bank.
2. Integration with Existing Video Storage: Does the Video CDN seamlessly integrate with your existing video streaming and video storage infrastructure? This integration allows for efficient content management, simplifies the workflow, and ensures smooth adoption of the CDN without the need for significant changes in your existing setup.
3. Video Optimization: Look for a Video CDN with advanced video optimization features. This includes adaptive bitrate streaming, transcoding, and video compression techniques. These features optimize video quality and bandwidth consumption, ensuring optimal playback on various devices and network conditions.
4. Transparent Pricing: Evaluate the pricing structure of the Video CDN. Seek a provider offering transparent pricing with clear details on the pricing tiers, usage-based charges, and additional costs. Transparent pricing ensures you clearly understand the costs involved, allowing you to make informed decisions based on your budget and specific requirements.

Conclusion

In this blog post, we have explored the world of Video Content Delivery Networks (CDNs) and how they revolutionize the way online video streaming is delivered to viewers worldwide. We began by defining a Video CDN as a specialized CDN designed specifically to support video stream delivery and learned how they’re specialized for live streams and VODs alike in the areas of encoding, packaging, transcoding, storage, and delivery.