H265 HEVC Overview and Comparison With H264 AVC

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  • 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