Digital Media

数字媒体 (Digital Media) is a general term for text, audio, images, video, software, and interactive content that are represented as digital data and processed by electronic systems. It describes the methods of representing and processing information, rather than a specific type of optical disc, storage medium, or file format. CDs, hard drives, flash memory, and web servers can all store 数字媒体, and the same content can be transferred to different media without altering its underlying data.

Digitization involves sampling and quantizing continuous signals, or generating discrete data directly via a computer. Audio can be represented as PCM samples or encoded as data streams such as FLAC or AAC; images and video consist of pixels, frames, color parameters, and compression schemes. Digital representation allows data to be precisely replicated when error correction and integrity conditions are met, but lossy encoding, format conversion, signal processing, or transmission errors may still alter the content. File containers, encoding formats, transmission protocols, and storage media exist at different levels. Containers such as MP4 and Matroska organize video, audio, subtitles, and metadata; codecs such as H.264, HEVC, and AAC specify how signals are compressed; protocols such as HTTP and RTP handle transmission; and optical discs, hard drives, or NAND flash memory store the bits. In everyday language, these layers are often collectively referred to as “formats,” but in technical descriptions, they must be distinguished.

数字媒体 can exist as a local file or be delivered via download, on-demand streaming, or live transmission. Downloads typically result in a data copy that can be stored independently; streaming media receives segments as playback progresses, and whether a locally accessible copy is retained depends on the application and permission mechanisms. Cloud-based content still relies on physical servers and network infrastructure; “digital” does not mean it lacks a physical medium.

Describing digital audio and video typically requires multiple sets of parameters. For audio, these include sample rate, bit depth, channels, encoding, and bitrate; for video, they include pixel dimensions, frame rate, scanning method, chroma subsampling, bit depth, transfer function, and encoding. File extensions or platform identifiers can only convey a portion of this information: Two files with the same `.m4a` extension may use different audio codecs, and videos labeled “4K” may have different frame rates, dynamic ranges, and compression quality.

Digital content may also include metadata such as titles, creators, timestamps, languages, cover art, chapters, permissions, and checksums. Some metadata is embedded in the file, while other parts are stored in databases or transport lists; not all of it is necessarily preserved during migration, transcoding, or platform export. The accessibility of 数字媒体 therefore depends on whether the data is complete, whether a decoder for the format is available, and whether encryption, licensing, or online services remain valid.