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H.265/HEVC Overview and Comparison with H.264/AVC
Francisco Aguirre-Ramos : [email protected]
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