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HEVC Encoder

What is HEVC?

HEVC or High Efficiency Video Coding is a video compressing standard that was developed in 2010 by the ISO/IEC Moving Picture Experts Group (MPEG) and ITU-T Video Coding Experts Group (VCEG). HEVC codec is a coding standard based on the general structure of previous standards but with an improved HEVC encoder.

In 2005, VCEG started by creating a software known as KTA (Key Technical Areas) that evaluates the validity of proposals that were being presented. They were targeting a 25% bit rate reduction and a 50% reduction on the complexity of the process of encoding and decoding. In 2007 MPEG began a similar research with a target of 50% bit rate reduction and were only able to make a 20% reduction by 2009. It is at this point that the two companies merged and came up with the HEVC codec standard. A committee of experts was formed and the HEVC codec draft was completed on February 2012. The final Draft International was approved on 25th January, 2013, and the ITU-T published the standard on its website as a free download in June that same year.

HEVC Encoder/Encoding

The HEVC encoder compresses the frames into a compressed video bit stream which can be stored or transmitted. It begins by splitting a single frame into multiple portions. Each portion is called a Coding Tree Unit (CTU) which can be further divided into Coding Units (CU). Once the picture in the frame has been partitioned the predicting processes begin where a Coding Unit (CU) is partitioned further into Prediction Units (PUs). The HEVC converter uses two types of predictions namely intra prediction and inter prediction. Intra prediction predicts PUs from neighboring image data i.e. from the same picture frame. Inter prediction uses motion compensated prediction to predict PUs referenced from image data in pictures found before or after the current display i.e. other picture frames in the stream. Any data remaining after prediction is put into a block using a Discrete Cosine Transform (DCT).

The HEVC encoder applies these blocks to the remaining data in each CU. Finally, the coded bit stream is encoded further using Context Adaptive Binary Arithmetic Coding (CABAC) through a process known as Entropy encoding. This is the final step where the HEVC encoder arranges and compresses the transformed data into its separate components namely, motion vectors, prediction modes, partitioning information and other header data. At this point the video has been compressed and can be stored. For video transmission the HEVC encoder decodes the data in order to view images from a video source. By entropy decoding the  HEVC converter extracts the elements of the encoded sequence. It rescales and inverts the transform stage of the encoding process, units of the picture are restored to their original form, predicted and the predictions are added to the output of the inverse transform. The final step to viewing the motion picture is the process of reconstruction of the decoded video for viewing. Developed from the previous standard H.264/AVC HEVC codec has been tested and proven to have better resolution at various bit rates. The quality of resolution largely depends on the opinion of the viewer, the type of encoder and the characteristics of the video clip.

Compared to its predecessors, H264 and MPEG-4 AVC, HEVC codec has improved in quality of resolution and parallel processing functions. Recently MulticoreWare released the x265 standard intended to compete with HEVC codec (H265) on the open source market.

HEVC and 4K: The Future of Video

In conclusion, HEVC codec is the latest video coding software in the market that performs twice as well as its predecessors thanks to its developed HEVC encoder. It promises a future generation of HDTV (with 4K resolution) displays and data capture systems of superior quality resolution. HEVC codec undoubtedly has many competitors out there grappling to better the coding standard. This should not worry any party, be it the users or designers because all efforts culminate to the success of the world. As ITU-T Video Coding Experts Group (VCEG) merged with ISO/IEC Moving Picture Experts Group (MPEG) to create a new generation codec, so shall future codec designs emerge; a culmination of ideas from various coding designers.