In which method is one frame compared to a reference frame earlier?

The method where one frame is compared to a reference frame that comes earlier is known as Interframe Coding. This technique is foundational in video compression, as it efficiently reduces the amount of data needed to represent the video by only storing the differences or changes between successive frames instead of storing each frame in its entirety.

Interframe Coding works by analyzing the current frame in relation to one or more previous frames. If most of the information in the current frame is similar to that of the reference frame, this approach can represent the current frame with a significantly smaller amount of data. By encoding only the differences, it optimizes storage and transmission bandwidth, making it a highly effective method for streaming and storing video content.

In comparison, other methods such as Image Compression and Intraframe Coding do not involve referencing previous frames. Instead, Intraframe Coding encodes each frame independently, which may be less efficient in terms of compression ratios for video sequences. Frame Compression isn't a specific widely recognized term in this context and may lead to confusion about what aspects of compression are being discussed. Therefore, Interframe Coding is the correct answer when considering methods that leverage temporal redundancy by referencing earlier frames.