Introduction to digital video compression

Digital video compression encompasses a suite of techniques designed to minimize video file sizes, leveraging spatial and temporal redundancies for efficient storage and transmission.

Definition of digital video compression

Digital video compression is the application of digital media compression techniques to video data, aiming to significantly reduce the size of video files for efficient transmission and storage.

Principles of digital video compression

The compression of digital video is based on the presence of redundancy within video data, which can be spatial or temporal. Spatial redundancy refers to the similarity between pixels within a single frame, while temporal redundancy arises from similarities between consecutive frames.

Hybrid coding methods

Digital video compression typically employs hybrid coding methods that integrate transform coding, motion estimation, motion compensation, and entropy coding to achieve efficient compression.

Inter prediction and inter-frame coding

Inter prediction leverages temporal correlation to predict current image pixels using adjacent pixels from previously encoded images. This process involves motion estimation to find the best matching blocks and motion compensation to calculate the estimated values, effectively reducing temporal redundancy.

Predictive coding frames

Video compression involves dividing frames into ：

• I frames (key frames),
• P frames (forward predicted frames),
• B frames (bi-directional predicted frames).

These frames are used to represent still images within the video sequence, with I frames capturing complete images, P frames representing differences from the last key frame, and B frames recording differences relative to both preceding and following frames.

Development of video encoding standards

The history of video coding standards includes：

• MPEG-1 (introduced in 1993 for VCD and MP3),
• MPEG-2 (1994, for DVD and broadcast digital TV),
• MPEG-4 (1999, promoting network video),
• MPEG AVC/H.264 (launched for high-quality playback under limited bandwidth conditions).

In summary, digital video compression is a sophisticated process that harnesses the redundancy within video data to achieve substantial reductions in file size, facilitated by a series of evolving video encoding standards that have transformed the landscape of digital media.