Video Compression Standards
Selecting the Right Video Codec
Video compression reduces the quantity of data used to represent video content, making video files smaller with little perceptible loss in quality. Compressed files are easier to transmit over a network and easier to store.
The Video Codec
A video codec is a software module that enables video compression or decompression of digital video. Codecs encode a stream or signal for transmission, storage, or encryption and decode it for viewing or editing.
Lossless vs. Lossy Video Compression
Video can be compressed using either lossless or lossy methods. With lossless compression, each pixel is unchanged, resulting in an identical, bit-for-bit image after decompression. With lossy compression, the resulting video sequence is different from the original, but good enough for use. In most cases, lossy methods produce much smaller compressed files than lossless methods, while still meeting the requirements of the application.
Codec Standards
All of the following codecs are lossy, so the reconstructed image following compression is not exactly like the original.
- H.264 also known as MPEG-4 AVC or MPEG-4 part 10, provides better image quality at lower bit rates, substantially compared to MPEG-4 and MPEG-2. The H.264 compression standard can reduce image size by up to 50 percent increasing the use of network bandwidth and storage. The H.264 Main Profile (MP), used by the Nextiva S1800e Series, offers more sophisticated entropy-encoding strategies than the typical Baseline Profile.
- MPEG-4 is the most widely used codec for video security and offers better quality than MPEG-2, with supported resolutions from CIF/3.75 fps at 128 kbps to D1/30 fps at 6 Mbits/s. Most video surveillance implementations use the Simple (SP) or Advanced Simple Profile (ASP).
- MPEG-2 produces high-quality video at a lower compression ratio and higher bit rate, with the frame rate locked at 25 fps (PAL) and 30 fps (NTSC). The MPEG-2 Simple Profile uses very similar technologies to MPEG-4, ensuring the compression rate and image quality to be similar.
- SM4, is a proprietary, MPEG-4 based Verint codec designed to encode quickly and provide good perceptual quality, while reducing the required bit rate by about 5 percent when compared to the MPEG-4 Simple Profile.
- WMV9 (VC-1) is Microsoft’s Windows Media Video version 9 codec, a proprietary codec for low bitrate, streaming applications.
- MJPEG (Motion JPEG) is an informal name for multimedia formats in which each frame of a video sequence is separately compressed as a JPEG image. M-JPEG is often used by IP-based video cameras via http streams.
Choosing the Right Codec
Codec performance is generally a tradeoff between bitrate and image quality. Before choosing a codec, define your requirements keeping the following in mind:
- The maximum and minimum required sustained frame rate
- Whether recording/monitoring is required at all times or only when motion or an event occurs
- The resolution/frame rate required when recording motion, an event, or an alarm
- The length of time a video sequence must be stored
- The level of latency that is acceptable
- System robustness and security issues
- How much network bandwidth is required
Codecs for Nextiva Intelligent Edge Devices
Nextiva edge devices help optimize digital video with state-of-the-art video compression, and dual- and triple-streaming capabilities. By supporting various codecs: H.264, MPEG-4, SM4 and MJPEG, Verint delivers the appropriate codec and optimal solution to meet project objectives and requirements. Although proprietary codecs, such as SM4, are useful and provide excellent compression results, open, standards-based codecs, such as H.264 Main Profile and MPEG-4 Simple Profile, provide even more system flexibility.
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