FORMAT



HEVC/H.265

Since 2013 a standard for audiovisual applications recommended by ITU

High Efficiency Video Codec (HEVC) is a data reduction process, used to process media. This codec is also known as H.265 or MPEG-H Part 2. HEVC is the successor to the widely-used H.264 codec , the compression capabilities of which enabled mobile video applications, high-resolution video content on the web as well as the transmission of HDTV.

H.265 offers a high performance compression codec for disseminating video signals at lower bitrates, and is particularly useful in the delivery of UHD content to consumer devices.

This codec is characterised by its ability to achieve nearly twice the efficiency of H.264 encoded video content, while maintaining image quality. This is particularly suitable as a distribution codec. Applications of this codec can be found in the transfer of UHD TV, Blu-ray discs with 4K (UHD) resolution or for streaming applications. The video calling function on the latest iPhone models is based on HEVC encoding. Furthermore, the codec is used in the DVB-T2 transmission system.

HEVC achieves its compression performance by a motion prediction of the individual pixels on the current image, based on values of pixels from previous frames. Further processing is then applied on the basis of these difference values. The more accurate this motion estimation, the lower the number of differences that need to be transmitted – saving bandwidth. Additionally, HEVC uses flexible macroblock sizes. Macroblocks are elements that are used in codecs for viewing and evaluation. In H.264, the macroblocks are defined to 16x16 pixels. HEVC uses multiple blocks of up to 64x64 pixels. Thus redundancies and movements are found between different sized image areas or objects, which is a benefit, especially at higher resolutions such as HD or UHD.

As with any new codec, a lot of computing power is needed for this motion compensation and determining redundancies, which is why HEVC hardware-encoding is still quite expensive. The HEVC decoder on the other hand, is no more complex than the H.264 decoder. 1080p50 signals can be decoded on a standard tablet in real time. TV receivers still need a HEVC-enabled chip in the receiver for decoding. Depending on the application, there are dedicated hardware or software decoder solutions – but some, in the case of TVs or set top boxes – may mean replacing your hardware.

Aside from the enormous data-reduction and enabling the bandwidth efficient transmission of UHD content, HEVC provides other features - the codec can scale from resolutions of 320 × 240 pixels up to 8192 × 4320 pixels. The codec is future-proofed, at least until the next big standard shift to 8K. Bit rates from 8 to 16 bits are supported, colour sampling from 4: 2: 0 to 4: 4: 4, and frame rates up to 300fps are also provided in the respective levels of codecs.

This codec paves the way for new technologies such as HDR (High Dynamic Range), in addition to a higher resolution and a much higher contrast than can usually be transferred.