transcoding from h.264/avc to hevc

Transcoding from H.264/AVC to HEVC

Shantanu Kulkarni

UTA ID: 1000789943

Introduction to Transcoding

Video transcoding is the operation of converting video from one format to another.

A format is defined by characteristics such as bit-rate, spatial resolution etc.

Transcoding is one of the most promising technologies, which provides video adaptation in terms of bit-rate reduction, resolution reduction and format conversion to meet various requirements

Following is the most basic transcoding architecture

Fig. 1 Basic architecture for transcoding [8]

Need for Transcoding

Design of most video coding standards is primarily aimed at having the highest coding efficiency, which is the ability to encode the video at lowest possible bitrate while maintaining certain level of video quality.

HEVC, which is a recently emerged video coding standard, aims at high coding efficiency while retaining the video quality

With its hybrid coding architecture, motion compensation prediction and transform coding technique, it can be seen as an improved version of the previous standard H.264 [6]

Need for Transcoding contd.

Transcoding from H.264 to HEVC will enable lowering the bitrate resulting in a more efficient compression.[1]

AVC and HEVC share a similar prediction, transform, quantization, and entropy coding architecture. [1]

Overview of HEVC

The HEVC standard is based on the well-known block-based hybrid coding architecture, combining motion-compensated prediction and transform coding with high-efficiency entropy coding

It employs a flexible quad-tree coding block partitioning structure that enables the efficient use of large and multiple sizes of coding, prediction, and transform blocks.

It also employs improved intra prediction and coding, adaptive motion parameter prediction and coding, new loop filter and an enhanced version of context-adaptive binary arithmetic coding (CABAC) entropy coding.

Overview of HEVC contd.

Fig. 2 HEVC encoder block diagram

Overview of HEVC contd.

Fig. 3 Block based architecture HEVC – Intra-Prediction [17]

Overview of H.264/AVC [6]

Directional spatial prediction for intra coding (9 directional prediction modes)

Variable block-size motion compensation with small block size

Quarter-sample-accurate motion compensation Motion vectors over picture boundaries Multiple reference picture motion compensation Decoupling of referencing order from display order In-the-loop deblocking filtering

H.264/AVC Encoder-Decoder Block Diagram

Fig. 4 H.264/AVC Encoder [2]

Fig. 5 H.264/AVC Decoder [2]

Comparison of AVC & HEVC Larger block structure leading to maximum of 64x64

pixels per block Intra prediction direction modes which are upto 35 (33

modes + DC + Planar) in case of HEVC while H.264 has 9 directional modes of intra prediction

Adaptive motion vector prediction, which allows codec to find more inter frame redundancies

Superior parallelization tools, including wavefront parallel processing, for more efficient coding in a multi core environment

Entropy using CABAC only, no more CAVLC Improvements to de-blocking filter and addition of one

more filter called Sample Adaptive Offset (SAO) that further leaves artifacts along block edges

HEVC Transcoder The transcoding schemes discussed here avoid high computational

complexity in terms of reduced RDO evaluations and motion compensation operation as well as fractional pixel interpolation operation.

AVC Decoder

HEVCRe-encoder

Simplified Mode

Selection

Input AVC Bitstream

Output HEVC Bitstream

Residual, modes and MVs CU, PU partitions

and MVs

Fig. 6 Pixel domain AVC-HEVC transcoder[1]

HEVC Transcoder Contd.

The LCU will initially split according to the input MB modes in AVC The initial CU partitions will be further merged to larger size

according to the predict directions of its adjacent four sub-CUs. For example, if the predict directions of adjacent four 8x8 CUs are

the same, they will be merged to 16x16. Similar merge operations will also perform on CUs larger than 8x8. The merge process is applied from the 4x4 smallest 4x4 blocks to the blocks with size 32x32.

The input information from AVC can be used to reduce the candidate predict directions for SATD, or reducing the candidate SATD list

HEVC Transcoder contd.

The major complexity of Inter picture coding comes from the motion estimation (ME), MC operations when testing every set of possible coding parameters with possible CU size, PU and TU modes.

Thus, it is proposed to reduce these operations with the help of input

AVC information, e.g. residuals, modes and MVs.Since the largest CU (LCU) in HEVC consists of 16 MBs in AVC, after AVC decoding, the information of these MBs will transmit to the mode selection module.

HEVC Transcoder Contd.

Since the input AVC bitstream already contains useful information of the MB partitions and prediction directions, we extract the information which can be utilized by HEVC encoder without having to do any computations.

Key technology of AVC to HEVC transcoding consists of merging smaller blocks to a larger CU, especially for bit rate reduction transcoding. Since a large CU may consists of different 4x4 blocks, and probably, these blocks may have different MVs, merging these blocks now turns to measure the RD cost when the MV changes.

Cascaded encoder decoder transcoder architecture

Includes complete decoding and re-encoding High Complexity Error due to the lossy encoding of already decoded bit sequence

H.264 Encoder H.264 Decoder HEVC Encoder HEVC Decoder

Input Bit stream

Output Bit stream

H.264 Bit stream

Transcoded HEVC

Bit stream

Cascaded Decoder and Encoder

Reconstructed Bit stream

Fig.7 Cascaded encoder – decoder transcoder

Simulation results

Sequence Component Metric Encoded by H.264

Encoded by HEVC

Transcoded output with respect to

original


H.264

akiyo_qcif

YMSE 7.9453 16.3527 14.9827 13.0089

PSNR 39.14 35.9949 36.3749 36.9884

UMSE 4.89645 73.6801 7.6814 5.4491

PSNR 41.234 39.4573 39.2764 40.7675

VMSE 4.05427 44.4938 5.099 3.8215

PSNR 42.054 41.6478 41.056 42.3084

PSNR (color) 39.766 37.13431 37.322725 38.1257875

Bitrate (kbps) 15.53 12.4128 11.64

Computation Time (sec) 149.847 504.537 494.878

Table 1. MSE and PSNR of akiyo_qcif.yuv video sequence for 100 frames

Simulation results continued…


Encoded by HEVC


original


H.264

foreman_qcif

YMSE 16.03446 29.9875 16.0345 23.6761

PSNR 36.134 33.3614 36.0803 34.3877

UMSE 5.56395 7.3461 5.5639 3.5923

PSNR 40.689 39.4702 40.677 42.577

VMSE 4.00861 5.8822 4.0086 3.9526

PSNR 42.124 40.4354 42.1009 42.1619

PSNR color 37.452125 35.00925 37.4074625 36.3831375

Bitrate (kbps) 90.6 45.8904 43.4808


Table 2. MSE and PSNR of foreman_qcif.yuv video sequence for 100 frames



Encoded by HEVC


original


H.264

mobile_cif

YMSE 33.74791 60.16589 29.5597 48.6284

PSNR 33.021 30.3373 33.4238 31.2619

UMSE 16.33582 19.1911 24.0076 9.5459

PSNR 36.033 35.2998 34.3273 38.3326

VMSE 17.23845 22.2633 26.3195 12.7897

PSNR 35.806 34.6549 33.928 37.0622

PSNR color 33.745625 31.49731 33.5997625 32.870775

Bitrate (kbps) 851.1 361.4736 337.5528


Table 3. MSE and PSNR of mobile_cif.yuv video sequence for 100 frames



Encoded by

HEVC

Transcoded output

with respect to

original

Transcoded output

with respect

to H.264

coastguard_cif

YMSE 43.65598 54.3388 33.7838 32.0597

PSNR 31.797 30.7797 32.8437 33.0712

UMSE 3.745 3.7246 21.7963 1.75509

PSNR 42.499 42.42 34.747 45.6878

VMSE 3.11601 2.9498 24.5536 1.4232

PSNR 43.26 43.4328 34.2296 46.5979

PSNR color 34.567625 33.81638 33.25485 36.3391125

Bitrate (kbps) 428.1 295.2936 233.5488


Table 4. MSE and PSNR of coastguard_cif.yuv video sequence for 100 frames

Comparison of PSNR for colored images between ‘qcif’ video sequences akiyo and foreman

Video Sequences

PS

NR

(d

b)

Fig 8. PSNR Video sequences: akiyo_qcif and foreman_qcif

3434.5

3535.5

3636.5

3737.5

3838.5

3939.5

40

PSNR_akiyo_qcif PSNR_foreman_qcif

Encoded by H.264

Encoded by HEVC

Transcoded output withrespect to original

Transcoded output withrespect to H.264reconstructed frames

Video Sequences

PSNR (dB)

Comparison of PSNR for colored images between ‘cif’ video sequences mobile and coastguard

Fig 9. PSNR Video sequences: mobile_cif and coastguard_cif

3030.5

3131.5

3232.5

3333.5

3434.5

3535.5

3636.5

37

PSNR_mobile_cif PSNR_coastguard_cif

Encoded by H.264

Encoded by HEVC

Transcoded output withrespect to original


Video Sequences

PSNR (dB)

Comparison of bitrate for akiyo_qcif video sequence

1010.5

1111.5

1212.5

1313.5

1414.5

1515.5

16

Bitrate_akiyo_qcif

Encoded by H.264

Encoded by HEVC


Fig 10. Bitrate comparison between H.264 encoded, HEVC encoded and transcoded output using foreman_qcif.yuv sequence. (100 frames)

Video Sequences

Bitrate (kbps)

Comparison of bitrate for foreman_qcif video sequence

Fig 10. Bitrate comparison between H.264 encoded, HEVC encoded and transcoded output using foreman_qcif.yuv sequence. (100 frames)

404550556065707580859095

100

Bitrate_foreman_qcif

Encoded by H.264

Encoded by HEVC


Video Sequences

Bitrate (kbps)

Comparison of bitrate for mobile_cif video sequence

Fig 11. Bitrate comparison between H.264 encoded, HEVC encoded and transcoded output using mobile_cif.yuv sequence. (100 frames)

200250300350400450500550600650700750800850900

Bitrate_mobile_cif

Encoded by H.264

Encoded by HEVC


Video Sequences

Bitrate (kbps)

Comparison of bitrate for coastguard_cif video sequence

Fig 12. Bitrate comparison between H.264 encoded, HEVC encoded and transcoded output using coastguard_cif.yuv sequence. (100 frames)

200

225

250

275

300

325

350

375

400

425

450

Bitrate_coastguard_cif

Encoded by H.264

Encoded by HEVC


Video Sequences

Bitrate (kbps)

100125150175200225250275300325350375400425450475500525550

Computation Time Akiyo

Encoded by H.264

Encoded by HEVC


Fig 13. Computation time comparison between H.264 encoded, HEVC encoded and transcoded output using akiyo_qcif.yuv sequence. (100 frames)

Comparison of computation time for akiyo_qcif video sequence

Time(sec)

Video Sequences

Fig 14. Computation time comparison between H.264 encoded, HEVC encoded and transcoded output using foreman_qcif.yuv sequence. (100 frames)

Comparison of computation time for foreman_qcif video sequence

100150200250300350400450500550600650700750800850900

Computation Time Foreman

Encoded by H.264

Encoded by HEVC


Time(sec)

Video Sequences

Fig 15. Computation time comparison between H.264 encoded, HEVC encoded and transcoded output using mobile_cif.yuv sequence. (100 frames)

Comparison of computation time for mobile_cif video sequence

500750

1000125015001750200022502500275030003250350037504000

Computation Time Mobile

Encoded by H.264

Encoded by HEVC


Time(sec)

Video Sequences

Fig 16. Computation time comparison between H.264 encoded, HEVC encoded and transcoded output using coastguard_cif.yuv sequence. (100 frames)

Comparison of computation time for coastguard_cif video sequence

500750

10001250150017502000225025002750300032503500375040004250

Computation Time Coastguard

Encoded by H.264

Encoded by HEVC


Time(sec)

Video Sequences

Images Akiyo_qcif and Foreman_qcif

Fig 17. Akiyo_qcif video sequence 17a) H.264 encoded, 17b) transcoded and 17c) HEVC encoded and reconstructed

Fig 18. Foreman_qcif video sequence 18a) H.264 encoded, 18b) transcoded and 18c) HEVC encoded and reconstructed

Fig 17a. Fig 17b. Fig 17c.

Fig 18a. Fig 18b. Fig 18c.

Images Mobile_cif

Fig 19a. Mobile_cif H.264 encoded and reconstructed Fig 19b. Mobile_cif Transcoded

Fig 19c. HEVC Encoded and reconstructed

Images coastguard_cif

Fig 20a. Coastguard_cif H.264 encoded and reconstructed

Fig 20b. Coastguard_cif Transcoded

Fig 20c. Coastguard_cif HEVC Encoded and reconstructed

References1. D. Zhang, B. Li, J. Xu, and H. Li, ‘Fast Transcoding from H.264/AVC to High Efficiency Video

Coding’ IEEE International Conference on Multimedia Expo, pp. 651-656, July, 20122. T. Wiegand et al, “Overview of the H.264/AVC video coding standard,” IEEE Trans. CSVT,

Vol. 13, pp. 560-576, July 2003.J Xin, C.W. Lin and M.T. Sun, “Digital video transcoding”, Proceedings of the IEEE, Vol. 93, pp 84-97, Jan 2005.

3. T. Wiegand, G. J. Sullivan, G. Bjøntegaard, and A. Luthra, ‘Overview of the H.264/AVC Video Coding Standard’, IEEE transactions on circuits and systems for video technology, vol. 13, no. 7, pp. 560-576, July 2003

4. I. Kim, J. Min, T. Lee et al, ‘Block Partitioning Structure in the HEVC Standard’, IEEE transactions on circuits and systems for video technology, vol. 22, no. 12, pp. 1697-1706, December 2012

5. G. Sullivan, P. Topiwalla and A. Luthra, “The H.264/AVC video coding standard: overview and introduction to the fidelity range extensions”, SPIE Conference on Applications of Digital Image Processing XXVII, vol. 5558, pp. 53-74 Aug 2004.

6. T. D. Nguyen et al, “Efficient MPEG-4 to H.264/AVC transcoding with spatial downscaling”, ETRI Journal, vol.29, no.6, pp 826-828, Dec. 2007.

7. G.J. Sullivan, J. Ohm, W. Han et al, “Overview of High Efficiency Video Coding (HEVC) Standard” IEEE Transactions on Circuits and Systems for Video Technology, Vol. 22, No.12, Dec 2012

8. A. Vetros, C. Christopoulos and H. Sun, “Video transcoding architectures and techniques: An overview”, IEEE Signal Processing Magazine, Vol. 20, pp 18-29, March 2003

9. HEVC open source software (encoder/decoder) https://hevc.hhi.fraunhofer.de/svn/svn_HEVCSoftware/tags/HM-6.0

10. JM Reference Software - http://iphome.hhi.de/suehring/tml/ - H.264 reference software11. Eduardo Peixoto Fernandes da Silva, “Advanced Heterogeneous Video Transcoding” Queen

Mary, University of London, PhD Thesis.12. J. Padia, “Complexity Reduction For Vp6 To H.264 Transcoder Using Motion Vector Reuse”,

MPL, University of Texas at Arlington, May 2012.

References Contd.

Reference Books9. K. Sayood, “Introduction to Data compression”, III edition, Morgan Kauffmann publishers, 2006.10. I.E.G. Richardson, “H.264 and MPEG-4 video compression: video coding for next-generation

multimedia”, Edition II ,Wiley, 2010.

Websites11. http://en.wikipedia.org/wiki/ : Website for Wikipedia, Encyclopedia12. http://www-ee.uta.edu/Dip/Courses/EE5359/index.html: Course website13. http://ieeexplore.ieee.org/: Website archive for IEEE papers online14. http://www.v-net.tv/hevc-is-game-changer-for-multi-screen-and-iptv/: Impact of HEVC standard on

digital media market like cell phones, TVs etc15. http://www.streamingmedia.com/Articles/Editorial/What-Is-.../What-Is-HEVC-(H.265)-87765.aspx:

Summary about HEVC , information site.16. http://mrutyunjayahiremath.blogspot.com/2010/09/h264-video-codec_22.html: Diagram for H.264

prediction direction modes17. http://opticalengineering.spiedigitallibrary.org/article.aspx?articleid=1352660: Diagram for

Intra prediction block structure for HEVC

THANK YOU