Ashutosh Pandey, Technical Head, Network 18
Video compression is used to efficiently transport the content over large distance as well as sharing of content within the connected environment for treatment and production.
Compression is in the core of digital revolution that we all talk about and live in. Technically, Compression is the reversible process to reduce the number of bits needed to represent data that could be audio, video, image, or text.
This allows a more efficient storage and transmission of data. Video compression allows to optimally reducing the file size by analyzing the redundant information over different frames.
With reference to television and video industry, a simple calculation shows that an uncompressed video in standard definition need 216 Mbps. and high definition need 1.99 Gbps. Even with powerful computer systems, such data amount causes extreme-high computational demands for managing the data. Fortunately, digital video contains a great deal of redundancy. Thus it is suitable for compression, which can reduce these problems significantly. Video compression is thus used to efficiently transport the content over large distance as well as sharing of content within the connected environment for treatment and production.
JPEG and MPEG are the two basic compression standards. In broad terms, JPEG is associated with still digital pictures, whilst MPEG is dedicated to digital video sequences.
Video Compression Formats
MPEG-1. This compression technique is for efficient coding of a video sequence. The focus is on bit-streams of about 1.5 Mbps and originally for storage of digital video on CDs. The focus is on compression ratio rather than picture quality
MPEG-2. The MPEG-2 project focused on extending the compression technique of MPEG-1 to cover larger pictures and higher quality at the expense of a higher bandwidth usage. This provides more advanced techniques to enhance the video quality at the same bit-rate. The expense is the need for far more complex equipment.
MPEG-4. The important new features of MPEG-4 concerning video compression are the support of even lower bandwidth-consuming applications, e.g., mobile devices like cell phones, and on the other hand applications with extremely high-quality and almost unlimited bandwidth. In general the MPEG-4 standard is a lot wider than the previous standards.
H.264. This is the latest video compression standard (also known as MPEG-4 Part 10/AVC for advanced video coding) and is expected to become the video standard of choice in the coming years. This is a licensed standard that supports the most efficient video compression techniques available today. It reduces the size more than 80 percent compared to other standards without compromising image quality. H.264 uses much less network bandwidth and storage space required for a video file. This is where the economies of reduced bandwidth and storage needs will deliver the biggest savings. Widely used by service providers such as online video storage and telecommunications companies, it provides savings in network bandwidth and storage costs. It requires higher-performance network cameras and monitoring stations.
High-efficiency video coding (HEVC). Also known as H.265 and MPEG-H Part 2, is a video compression standard, one of several potential successors to the widely used AVC (H.264 or MPEG-4 Part 10). In comparison to AVC, HEVC offers about double the data compression ratio at the same level of video quality, or substantially improved video quality at the same bit rate. It supports resolutions up to 81924320, including 8K UHD.
Dynamic adaptive streaming over HTTP (DASH). Also known as MPEG-DASH, it is an adaptive bitrate streaming technique that enables high-quality streaming of media content over the Internet delivered from conventional HTTP web servers. Similar to Apple's HTTP Live Streaming (HLS) solution, MPEG-DASH works by breaking the content into a sequence of small HTTP-based file segments, each segment containing a short interval of playback time of content. The content is made available at a variety of different bit rates. While the content is being played back by an MPEG-DASH client, the client automatically selects from the alternatives the next segment to download and play back, based on current network conditions. The client selects the segment with the highest bit rate possible that can be downloaded in time for play back without causing stalls or re-buffering events in the playback. Thus, an MPEG-DASH client can seamlessly adapt to changing network conditions, and provide high-quality play back with fewer stalls or re-buffering events. Unlike, HLS, HDS, and smooth streaming, DASH is codec-agnostic, which means it can use content encoded with any coding format like H.265, H.264, VP9, etc.
MPEG-7. In MPEG-7, the content of the video (or any other multimedia) is described and associated with the content itself, for example, to allow fast and efficient searching in the material. MPEG-7 uses XML to store metadata, and it can be attached to a time code in order to tag particular events in a stream.
MPEG-21. It is a standard that defines means of sharing digital rights, permissions, and restrictions for digital content. MPEG-21 is an XML-based standard, and is developed to counter illegitimate distribution of digital content.
Video compression is gaining popularity since storage and network bandwidth requirements are able to be reduced with compression. Many algorithms for video compression, which are designed with a different target in mind, have been proposed. This explains the standardization efforts for video compression such as H.261, 263 and 263+, MPEG-1, 2, 4, 7 and H.264. Most recent efforts on video compression for video have focused on scalable video coding. The primary objectives of on-going research on scalable video coding are to achieve high compression efficiency, high flexibility (bandwidth scalability), and/or low complexity. Due to the conflicting nature of efficiency, flexibility, and complexity, each scalable video coding scheme seeks tradeoffs. Designers of video services need to choose an appropriate scalable video coding scheme, which meets the target efficiency and flexibility at an affordable cost and complexity. Compression is not only the factor to determine bandwidth, but modulation also plays an important role in saving the bandwidth. When we consider satellite broadcasting, satellite modulation also plays a vital role for effective video and audio bit rates. DVB-S has been a standard for modulation for TV broadcasting and satellite contribution, and now is largely replaced with upgraded and much efficient DVB-S2 mode.
Optimized modulation type, FEC, and roll-off factor provide much efficient bitrate utilization.
Technology solutions are intended at optimizing the medium bandwidth requirement while delivering high- experience content to the consumers – technology development is a continuous phenomenon aimed to impress and satisfy the ever-demanding consumer.