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Digital video technology has become a cornerstone in modern communications, computing, and broadcasting. It powers a wide range of applications such as video conferencing, video calling, digital television, and media storage, leading to the development of numerous video compression standards. These standards vary in performance, efficiency, and application scope. Below is a detailed comparison of some of the most commonly used video compression standards.
1. **MJPEG (Rarely Used)**
MJPEG stands for Motion JPEG, which is essentially a sequence of JPEG-compressed images played in rapid succession to create a video effect. It operates at 25 frames per second and is known for maintaining relatively good image quality. However, its compression ratio is limited, typically around 6:1, which means it requires more bandwidth. A single channel can consume about 2 Mbps. Since MJPEG is not a standardized format, different manufacturers often use their own versions, making interoperability difficult.
2. **MPEG-1**
MPEG-1 was widely used in VCDs and early digital video recorders (DVRs). Introduced in 1992, it was designed for devices with varying bandwidths, such as CD-ROMs and Video-CDs. It supports data transfer rates up to 1.5 Mbps and compresses video to resolutions like 360×240 (NTSC) or 360×288 (PAL). The compression ratio is around 1/100 to 1/200, making it suitable for basic video applications but not ideal for high-quality or high-bandwidth needs.
3. **MPEG-2**
MPEG-2 became the standard for DVDs and was introduced in 1994. It was developed for higher picture quality and higher transmission rates, supporting bitrates between 3–10 Mbps. It is compatible with MPEG-1 and can handle resolutions like 720×480 (NTSC) or 720×576 (PAL). While it offers superior image quality, it also requires significant bandwidth—between 4–15 Mbps—which makes it unsuitable for long-term storage or network transmission.
4. **MPEG-4**
Finalized in October 1998, MPEG-4 became an international standard in January 1999. It was designed for low-bitrate video compression and combines features from both MPEG-1 and MPEG-2. It supports bitrates ranging from 4.8 kbps to 64 kbps, with resolutions as small as 176×144. MPEG-4 uses efficient frame reconstruction techniques to deliver high-quality video with minimal data, making it ideal for mobile and web-based applications.
5. **H.263**
H.263 is a video coding standard developed by ITU-T, aimed at medium-to-high quality video compression at low bitrates. It offers a high compression ratio, especially in CIF format, where a single channel may occupy only a few hundred kilobits per second. However, its image quality is generally lower than other standards, and the required bandwidth can fluctuate significantly depending on the motion in the video.
6. **H.264 (AVC)**
H.264, also known as Advanced Video Coding (AVC), was jointly developed by ITU-T and ISO/IEC. It provides significantly better compression than previous standards, saving about 50% of the bit rate compared to H.263 and 64% compared to MPEG-2. It is widely used in video streaming, IP-based communication, and digital storage due to its efficiency and adaptability. However, it comes with higher computational complexity, requiring more processing power for encoding and decoding.
H.264 is divided into three main profiles: **Baseline**, **Main**, and **High**.
- **Baseline**: Designed for real-time applications, it offers low latency and fault tolerance.
- **Main**: Provides improved image quality and compression, suitable for SDTV, HDTV, and DVD.
- **High**: Optimized for streaming media, with advanced features for flexible bitstream access.
Today, when people refer to "MPEG-4," they usually mean the second part of the MPEG-4 standard (ISO 14496-2), which includes formats like DivX, XviD, and QuickTime. This standard remains widely used in various consumer and professional video applications.