High-definition videois a (digital) video system of higherresolutionthanstandard resolution (standard resolution broadcasts at the same (or similar) resolution as analog systems). File size is an important concern because High-definition Video files take a lot of storage space on hard drive. Therefore, various video compression algorithms (codec) are use to manipulate video signals to reduce the storage (to store more data in the same space) and to transfer it in less time or bandwidth while maximizing perceived video quality. Better compression means greater flexibility - the more efficiently data is handled,
Furthermore, all compression techniques are of: lossless and lossy. When a file is compressed in a lossless method, 100 percent of the data is still there, you can save lossless video over and over without any loss of data. Lossy compression discards data in order to achieve a lower bit rate. And every time you save your file in a lossy file format, it discards more of the data, even if you're saving it in the same format.
Common among all video compression techniques is the reduction of "invisible" details to achieve compression and reduce hard disk consumption and bandwidth demands. Effective compression is best achieved with a combination of data reduction techniques such as bit rate reduction and compression. The difference is that bit rate reduction eliminates unnoticeable data, and compression removes unnecessary and excessive data through mathematical algorithms. Due to different forms of redundancy and the fact that the human visual system is unable to detect certain details, information can be altered or removed causing changes that are imperceptible to the human eye or brain.Some of the more common image compression techniques in use today are: M-JPEG (JPEG), MPEG-1, MPEG-2, MPEG-4, H.264 (MPEG-4 Part10) (both ASP and AVC).
The ISO JPEG standard handles methods for continuous tone image compression for color and grayscale images. JPEG was designed for compression of still images and it makes no use of temporal redundancy which is a very important element in video compression techniques. M-JPEG (Motion JPEG) uses JPEG compression for each frame in a video stream. It has relatively low processor demands and has made possible the current generation of network cameras. It's also quite well suited to monitoring applications where it's not always essential to provide a TV-quality frame-rate. On the negative side, the M-JPEG format dates back to the early 90s and since then the technology of compression has advanced considerably. M-JPEG is a video codec where each video field (frame) is separately compressed into a JPEG image. The resulting quality of video compression is independent from the motion in the image (which differs from MPEG video where quality often decreases when footage contains lots of movement).
MPEG-1 approved as a standard in 1993, it provides VHS quality on a CD-ROM or Video CD (VCD). MPEG-1 is basically a standard for storing and playing video on a single computer at low bit-rates (that is, requiring low transfer capacity, thus lower bandwidth).
MPEG-2 was approved in 1994 as a standard for high quality digital video (DVD), digital high-definition TV (HDTV), interactive storage media (ISM), digital broadcast video (DBV) and cable TV (CATV).
The other standard form of compression, MPEG-4 is actually a series of standards, developed by ISO/IEC Motion Pictures Expert Group (MPEG). MPEG-4 compression not only operates on each individual frame (intra-frame compression) but also across a series of frames (inter-frame compression). Since a large amount of data is frequently unchanged between frames, this enables a highly significant increase in compression.
H.264 was developed to provide high-quality video at a much lower bit rate than standard MPEG-2, MPEG-4 or M-JPEG. As a result, H.264 compression represents a significant benefit to network security camera operations, offering enhanced images with reduced bandwidth.
Comparison of H.264, MPEG-4, and JPEG (picture quality vs. bit rate)
The vertical axis shows Peak Signal-to-Noise Ratio (PSNR), a metric for the "quality" of compressed video images, while the horizontal axis shows the transmission bit rate. The graph shows just one example of comparing bit rates at which JPEG, MPEG-4 and H.264 images can be transmitted. Actual bit rates for transmitting data using these three compression formats differ with image quality and image size settings. In this example, the video parameters are: 10 frames per second, 176x144 (QCIF) resolution, 10 seconds of video, (100 frames).
HD MPEG-2 content at 1920x1080 traditionally runs at 12-20 Mbps, while H.264 can deliver 1920x1080 content at 7-8 Mbps at the same or better quality. H.264 provides DVD quality at about half the data rate of MPEG-2. Because of this efficiency, H.264, an ISO standard, stands to be the likely successor to MPEG-2 in the professional media industry.
- Low-bandwidth availability
- Independent frames
- High bit rate / low compression
- Approved November 1993
- Enabled Video CD
- Enabled CD-ROM
- Enabled mp3 audio
- Approved November 1994
- Enabled Digital TV set-top boxes
- Enabled Digital Versatile Disk (DVD)
- Approved October 1998
- Scalable quality
- Based on QuickTime File Format
- Supports 3D objects
- Scalable delivery from cell phones to satellite TV.
H.264 (MPEG-4 Part 10)
- Completed May 2003 (continued to improve October 2009)
- Scalable from 3G to HD and beyond
- Full High Definition, HD-DVD and Blu-ray
- Exceptional quality at any size (DVD-quality video at under 1 Mbps)
- A revolution in quality and coding efficiency
Overall, MPEG-1, MPEG-2, MPEG-4 Part 2 and MJPG are still used in the industry today but H.264 is the leading video compression technology in the MPEG-4 standard, (it is also known as MPEG-4 Part 10). H.264 can match the best possible MPEG-2 quality at up to half the data rate. H.264 also delivers excellent video quality across the entire bandwidth spectrum from 3G to HD and everything in between (from 40 Kbps to upwards of 10 Mbps).
All of this development seems to have impact on the same direction: video communication will be a more common service in the future.
- ISO/IEC 11172: 'Coding of moving pictures and associated audio for digital storage media at up to about 1.5 Mbit/s'.
- ISO/IEC 13818: 'Generic coding of moving pictures and associated audio (MPEG-2)'.
- 'Encoding parameters of digital television for studios', CCIR Recommendation 601-1 XVIth Plenary Assembly Dubrovnik 1986, Vol. XI, Part 1, pp. 319-328.
- JAIN, A.K.: 'Fundamentals of digital image processing' (Prentice Hall, 1989).
- WELLS, N.D.: 'Component codec standard for high-quality digital television',Electronics & Communication Engineering Journal, August 1992,4, (4), pp. 195-202.
- CARR, M.D.: 'New video coding standard for the 1990s',Electronics & Communication Engineering Journal, June 1990,2, (3), pp. 119-124.
- RAO, K.R. and YIP, P.: 'Discrete cosine transform: algorithms, advantages, applications' (Academic Press, 1990).
- Introduction to video compression: Berkeley Design Technology, Inc.
- Video compression technology - H.264 explained, Yu Kitamura (Sony Professional Solutions Europe)
- MPEG - Motion Picture Experts Group. The committee responsible for developing the MPEG standards. Homepage at: www.mpeg.telecomitalialab.com
- JPEG - Joint Photographic Experts Group. The committee responsible for developing the JPEG and JPEG 2000 standards. Homepage at: www.jpeg.org
- ISO - International Standards Organization. A worldwide federation of national standards bodies fromsome 140 countries. Homepage at: www.iso.ch
- IEC - International Electro-technical Commission. International Electro-technical Commission. An international standards and conformity assessment body for all fields of electro technology. Homepage at: www.iec.ch
- ITU - International Telecommunications Union. An international organization within the United Nations System where governments and the private sector coordinate global telecom networks and services. Homepage at: www.itu.int