Codec

A codec — a portmanteau of coder-decoder — is a tool that encodes digital media files for storage or transmission before decoding them for playback or editing.

They make it easier to share and store quality content on all kinds of devices by cutting down file sizes. Audio codecs handle audio files, video codecs manage video files, and image codecs optimize still image data.

How Do Codecs Work?

Codecs take raw media data (like video or audio) and compress it into a smaller, more manageable size through a process known as encoding. 

When you need to use the media, they decompress the file into a format that's nearly as good as the original through a process known as decoding.

Media compression typically uses one of two techniques:

Transformative Compression

This type of compression reworks media data using mathematical techniques to break it into smaller pieces. It uncovers hidden patterns and repeated elements, shrinking the file size significantly.

Transformative compression is used in still-image compression (JPEG) and intra-frame video encoding, where each frame is compressed independently (e.g., Motion JPEG).

Predictive Compression

This compression technique uses similarities over time by comparing differences between consecutive frames or data blocks. Instead of storing complete frames, it encodes only the changes between them, significantly reducing bitrate requirements.

Most modern video codecs use predictive compression. High-Efficiency Video Coding (HEVC)/H.265, for example, uses motion compensation and inter-frame prediction for higher efficiency without a proportional loss in quality.

Pairing these methods with sophisticated rate control algorithms and perception optimization techniques balances smooth playback, storage space, and processing power.

Why Do We Need Codecs?

Codecs streamline development workflows and ensure your viewers experience high-quality, uninterrupted content.

Efficiency

These tools streamline content management and facilitate efficient processing by compressing high-resolution media files into more manageable sizes. 

This speeds up file transfers, which is especially important if you're working on a cloud-based 4K video conferencing tool and other real-time communication platforms.

Low Latency and Adaptability

In real-time communications like video calls, codecs quickly compress and decompress data to keep latency low and interactions smooth. 

With smaller file sizes, streaming content uses less bandwidth, allowing smoother on-demand videos and live streams, even on slower networks. 

Quality

Emerging AI-powered streaming algorithms can now fine-tune compression settings in real time. This allows advanced compression tools like AV1 and VVC to deliver higher quality at lower bitrates. But it also comes with more processing demands.

This technology works behind the scenes to simplify and streamline media management for developers.

Types of Codecs

Whether you're building a live-streaming platform or any other real-time communication app, it's crucial to understand the different types of codecs and how they work.

Lossy vs. Lossless Codecs

Before getting into specifics, let's examine how lossy compression techniques achieve smaller file sizes, laying the groundwork to compare them with lossless compression methods.

Lossy 

Lossy methods compress files by removing details we're less likely to notice. This approach reduces file sizes and saves storage space, although it may sometimes sacrifice some quality.

You would generally find these codecs in live-streaming applications where bandwidth conservation is crucial.

One example of a lossy codec is YouTube's VP9, which adjusts its compression based on available bandwidth, ensuring smooth playback without compromising video quality, even on slower internet connections.

Some other examples include:

• Audio: MP3 and AAC (used in Apple Music and YouTube)
• Video: H.264 (the most used video codec in streaming services) and VP8

Lossless 

Lossless methods preserve all original data while still reducing file sizes. They're used in archiving, professional audio production, and video editing, where maintaining the original quality is a top priority.

Popular lossless options include:

• Audio: FLAC and ALAC (Apple Lossless Audio Codec)
• Video: Motion JPEG and Apple ProRes

Though lossless formats deliver the highest quality, their larger file sizes make them impractical for real-time streaming and online playback.

Hardware vs. Software Codecs

Media encoding and decoding efficiency depends on whether the codec is processed via software or dedicated hardware acceleration.

Software-Based Codecs

These rely on the CPU for encoding and decoding media. For example, many open-source libraries — such as FFmpeg's libx264 for H.264 encoding or libvpx for VP8/VP9 — are software-based codecs that run on general-purpose processors. 

This approach offers flexibility and simplicity since you don't need specialized hardware. However, these solutions can be CPU-intensive, especially when encoding high-resolution videos in real time. This may lead to increased power consumption and potential performance bottlenecks on less powerful systems.

Hardware-Accelerated Codecs

They use specialized processing units such as Graphics Processing Units (GPUs), Application-Specific Integrated Circuits (ASICs), and Digital Signal Processors (DSPs) to handle encoding and decoding more efficiently. 

These dedicated solutions streamline professional video workflows. They offload computational workloads from the CPU, resulting in lower power consumption and faster processing.

As the name suggests, they require dedicated hardware, which results in higher upfront costs and more complex updates.

Some good examples include:

• NVIDIA NVENC: A hardware video encoder found in NVIDIA GPUs that provides low-latency, high-quality video encoding with minimal CPU overhead. It's used for live streaming, video editing, and cloud gaming applications.
• Apple ProRes hardware acceleration: Apple's ProRes format is optimized for pristine quality playback and low-latency video processing, with dedicated hardware acceleration in Apple's M1 and M2 chips, allowing seamless high-resolution video editing in Final Cut Pro and other software.

Commonly Used Audio, Image, and Video Codecs

Let's explore some of the different types of codecs, their specific media formats, and use cases. 

Still Image Codecs

Joint Photographic Experts Group (JPG/JPEG): A widely used lossy compression format for digital images, balancing quality and file size.

Tag Image File Format (TIFF): A lossless image format used for professional photography, printing, and archival purposes. It's the industry standard for consumer-level picture compression.

Portable Network Graphics (PNG): A lossless image format commonly used for web graphics because it promotes transparency and smaller file sizes without sacrificing image quality.

Audio Codecs

• MPEG-1 Audio Layer III (MP3): One of the most recognized lossy audio formats, MP3 efficiently compresses audio while maintaining decent quality, making it a standard for music distribution.

• Advanced Audio Coding (AAC): Designed as an improvement over MP3, AAC delivers better sound quality at similar bitrates and is widely used in streaming services like YouTube, Apple Music, and Spotify.

• Opus: A highly versatile option, Opus provides adaptive bitrate control and low latency. It's used in VoIP, video conferencing, gaming, and other real-time applications.

• Free Lossless Audio Codec (FLAC): Popular among audiophiles, FLAC provides lossless compression, preserving the original audio quality while reducing file size significantly.

• Global System for Mobile Communications (GSM): A low-bitrate speech compression tool optimized for mobile networks and voice calls.

• Internet Low Bitrate Codec (iLBC): Designed for VoIP and real-time communication, offering high-quality speech compression.

• Waveform Audio File Format (WAV): WAV is an uncompressed audio format used in professional audio recording and editing.

• Apple Lossless Audio Codec (ALAC): Apple's proprietary lossless format used in iTunes and Apple Music. It offers high-quality compression without any loss of audio fidelity. 

Video Codecs

• H.264 (AVC): This is the most dominant video option on the market today. H.264 provides a fair share of quality and file size, making it a preferred choice for video streaming services, Blu-ray discs, and video conferencing.

• H.265 (HEVC): The successor to H.264, H.265 offers up to 50% better compression efficiency, enabling higher resolutions like 4K and 8K while reducing bandwidth usage.

• Video Processing 9 (VP9): VP9 is Google's open-source alternative to H.265. It delivers high-quality video compression and is used on platforms like YouTube to optimize playback efficiency.

• Video Processing 8 (VP8): VP8 is another open-source option from Google. It was popular in the early, pre-VP9 days of YouTube.

• AOMedia Video 1 (AV1): A next-generation open-source tool backed by major tech companies, AV1 offers better compression efficiency than VP9 and H.265, reducing bandwidth costs while maintaining high video quality. However, adoption remains slow due to hardware decoding challenges.

• Apple ProRes: A high-quality, lossy video codec developed by Apple for professional video editing and post-production.

• Motion JPEG (MJPEG): MJPEG compresses each frame individually rather than using inter-frame compression. While inefficient for streaming, it's useful in video editing and security camera applications due to its simplicity and frame-by-frame clarity.

Choosing the Appropriate Codec

Selecting the right codec is a critical decision when developing real-time apps. You must balance factors like compression efficiency, visual or audio quality, latency, and compatibility with your target platforms. 

Livestreaming

If you're building a live streaming service, consider lossy options like H.264 for video and Opus for audio. They use inter-frame prediction and variable bitrate encoding to reduce file sizes and bandwidth consumption.

Adaptive Streaming

Protocols such as MPEG-DASH and CMAF are ideal for adaptive streaming. They help segment media into chunks and adjust quality levels based on available bandwidth.

Editing and Archiving

For video editing or archiving, consider lossless options like Apple ProRes for video or FLAC for audio. These options preserve every bit of detail by avoiding data loss during compression. However, this comes at the cost of increased storage and processing demands.

Integration

From an integration standpoint, you should use tools such as FFmpeg, which offers a suite of libraries for encoding, decoding, and transcoding media streams.

You can automate this on your backend through scripting or API calls to convert raw media into your desired format. You may also need to configure encoding parameters — like bitrate, GOP structure, and keyframe intervals — to optimize performance based on your app's specific use case.

Codec Packs

Because there are hundreds of compression options, using a codec pack can be a simple and efficient solution. A codec pack is a comprehensive bundle of multiple codecs put into a single installer, streamlining setup and ensuring compatibility across various media formats.

For instance, popular options like the K-Lite Codec Pack or CCCP allow you to install all the essential audio and video codecs at once.

Frequently Asked Questions