H.265/HEVC Overview and Comparison with H.264/AVC

Francisco Aguirre-Ramos : fjaguirre@ieee.org

Evolution

ITU-T Video Coding Experts Group (VCEG)

ISO/IEC Moving Picture Experts Group (MPEG)

VCEG + MPEG = Joint Collaborative Team on Video Coding (JCT-VC)

H.261 (VCEG)

1990

Video conferencing

MPEG-1 Part 2

(MPEG)

VCD Interactive CDs

H.262/MPEG-2

Video (JCT-VC)

DVD-V HDTV

H.263 (VCEG)

H.263V2

MPEG-4 Part 2

(JCT-VC)

Flash video

H.264/MPEG-4

Part 10 AVC

(JCT-VC)

Mobile applications Adaptive multi-bitrate

streaming

HDTV broadcasting Blu-ray Video 3DTV

1993

Are we missing

something?

1994 1995 - 1998 2003

Evolution (2)

H.265/MPEG-H Part 2 HEVC

Developed by the Joint Collaborative Team on Video Coding Designed to fulfil the requirements of the new video applications Focused on:

o Increased video resolution

o Parallel processing architectures

It will allow: o Full-HDTV broadcasting

o UHDTV (up to 8k*4k resolution)

o Mobile HD content

o Full-HD 3DTV

Provides an improvement of coding efficiency over AVC of 50% (half bitrate same quality)

HEVC encoding process is from 2x to 10x more complex than the one of AVC

Coding Process

We can resume the coding process into five

steps:

Partitioning Prediction Reconstruction Coding Packetization

Picture Partitioning

HEVC introduces a larger block structure than previous standards

A larger block structure provides a higher compression performance

Basic block is known as the largest coding unit (LCU), it can be

recursively split into smaller coding

units (CU)

The CU is used as the basic unit for intra- and intercoding

Picture Partitioning (2)

Prediction Units

Picture Partitioning (3)

Transform Units

A transform unit (TU) is the basic unit for the transform

and quantization processes

Size and shape of the TUs depend on the size of the PU

TUs can be as small as 4x4 or as large as 32x32

Picture Partitioning (4)

Example

Intra- and Interprediction

Intraprediction

Takes advantage of the spatial correlation within a picture

Interprediction

Takes advantage of the similarities of each picture with its temporal neighbors

Intraprediction

HEVC has 35 luma and 6 chroma intraprediction modes (H.264/AVC has 9 luma and 4 chroma intra modes)

Intraprediction (2)

Intraprediction can be performed at block sizes from 64x64 downto 4x4 (depending on

PU size)

For large PUs, mode-dependent intrasmoothing (MDIS) is used (basically a

low-pass filter is applied)

Interprediction

Asymmetric motion partitions (AMP) improve the coding efficiency (allows to fit PUs to

shapes in the picture)

The accuracy of motion compensation in HEVC is 1/4 pel for luma samples

Motion information is coded using advanced motion vector prediction (AMVP), merge and

skip modes are availables

Transform and

Quantization

HEVC applies square and non-square DCT-like integer transforms

Integer transforms used in HEVC are better approximations to the DCT than the used in

H.264/AVC

Integer discrete sine transform (DST) is used for some residuals

In-loop Filtering

HEVC applies 3 different in-loop filtering methods: o Deblocking filter: Similar to the one in H.264/AVC

o Sample Adaptive Offset (SAO): Classify pixels into

different categories and adds a simple offset to each

pixel based on its category

o Adaptive Loop Filtering (ALF): Its constructed based

on the original image and it's designed to minimize

the distortion between the reconstructed and the

original images

Coding: Tiles

Coding: Slices

Coding: WPP

Wavefront parallel processing (WPP) is an efficient

mechanism for parallel

encoding/decoding

Prediction dependencies are not broken across slices

The basic concept is to start processing a new row of LCUs

with a new parallel process as

soon as two LCUs have been

processed in the row above

HEVC vs AVC

References Ostermann, J., Bormans, J., List, P., Marpe, D., Narroschke, M., Pereira, F.,

Stockhammer, T., et al. (2004). Video coding with H.264/AVC: tools, performance, and

complexity. IEEE Circuits and Systems Magazine, 4(1), 728. doi:10.1109/MCAS.2004.1286980

Ohm, J., Sullivan, G. J., Schwarz, H., Tan, T. K., & Wiegand, T. (2012). Comparison of the Coding Efficiency of Video Coding Standards Including High Efficiency Video Coding (HEVC).

Sullivan, G. J., Ohm, J., Han, W., & Wiegand, T. (2012). Overview of the High Efficiency Video Coding (HEVC) Standard, (c).

Bross, B., Han, W.-J., Ohm, J.-R., Sullivan, G. J., & Wiegand, T. (2012). High Efficiency Video Coding (HEVC) Text Specification Draft 8 (pp. 1261).

Goldman, M. S. (2011). High Efficiency Video Coding (HEVC) The Next Generation Compression Technology. SMPTE Conferences, 2011(1), 111. doi:10.5594/M001098

Pourazad, M., Doutre, C., Azimi, M., & Nasiopoulos, P. (2012). HEVC: The New Gold Standard for Video Compression: How Does HEVC Compare with H.264/AVC? IEEE

Consumer Electronics Magazine, 1(3), 3646. doi:10.1109/MCE.2012.2192754