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【Thesis Interpretation】Performance Comparison of H.264 and H.265 Encoders for 4K Video Sequences

  • Level: IEEE
  • Authors: Jianing Li, Zhaohui Li, Dongmei Li
  • Time: 2016
  • Organization: Communication University of China
  • Download:Performance Comparison of H.264 and H.265 Encoders for 4K Video Sequences

summaries

  1. contexts: With the growing demand for Ultra-High Definition (UHD) in the TV industry, 4K Ultra HD technology is becoming the focus of industry attention.

  2. State of the art: Currently, the two most commonly used technologies for encoding 4K Ultra HD signals are H.264 encoding andHEVC(High Efficiency Video Coding, also known as H.265) encoding.

  3. research purpose: The purpose of this paper is to compare these two coding techniques by comparing theperformances, to evaluate their strengths and weaknesses in encoding 4K video sequences.

  4. Research methodology: The thesis employs two coding techniques fordifferent4K video sequences are coded and conclusions are drawn by analyzing and comparing the coding performance.

  5. Expected results: Through this comparison, the paper is expected to provide insights into the coding efficiency, quality, and speed of H.264 and H.265, and may indicate which technology is better suited to the coding needs of 4K video.

4k video development

  1. Development of the television industry: The television industry has been on a quest for moreperfectImage and sound. The development of digital technology has accelerated the increase in TV resolution from SD to HD and the emergence of 4K and 8K, which shows the current trend in the field of television.

  2. Advantages of 4K technology：

    • The amount of image information: 4K technology has four times more image information than HD, making the picture clearer and finer quality.
    • Frame rate and color gamut: 4K technology is more conducive to the display of fast motion by increasing the frame rate and expanding the color gamut, enabling the display of more image details and better reproduction of the real picture.
    • Viewing experience: 4K technology meets the audience's demand for high-definition image quality on a large screen, shortens the optimal viewing distance, and improves the sense of immersion.

  3. Rollout of 4K technology：

    • JAPAN: On October 27, 2013, the world's first live 4K HDTV demonstration was completed during a marathon in Osaka, Japan.
    • Japan: In June 2014, Japan began nationwide free trial broadcasts of 4K programs using HEVC/H.265 encoding technology with a channel signal frame rate of 60 fps.
    • South Korea: 4K channels using HEVC/H.265 encoding technology are also available in South Korea, with a channel signal frame rate of 60 fps and a bandwidth of 32 megabits per second.
    • CHINA: China is also developing 4K technology and in 2015, it launched its first 4K channel.

4k video encoding technology

  1. High bit rate for 4K signals: The bit rate of 4K TV signals is much higher than that of HDTV signals, which makes data transmission quite difficult.

  2. The need for efficient video coding technology: In order to solve the problem of high bit rate transmission, efficient video coding techniques are needed to compress and encode the original signal.

  3. H.264 coding and its test platforms：

    • Since its release in April 2003, H.264/AVC, a video coding standard jointly developed by ITU-T VCEG and ISO/IEC MPEG, has become the most widely used standard.
    • H.264 encoding for 4K image transmission requires that the 4K image be divided into four HD images and synthesized for transmission via satellite, which requires a higher bandwidth. For example, a 30fps 4K signal requires 40Mbps of bandwidth, while a 60fps signal requires about 80Mbps.
    • x264 is an open source H.264/MPEG-4 AVC video coding library that has evolved since 2003, especially with the addition of Dark, to become the more commonly used H.264/MPEG-4 AVC video encoder.
    • x264 offers a variety of parameter settings, including the PRESET system and the TUNE system, to simplify encoding inputs and recommendations, and to adjust the balance between encoding speed and quality.

  4. HEVC encoding and its testbed：

    • HEVC (High Efficiency Video Coding) is the latest video coding standard developed by ITU-T VCEG after H.264/AVC, adapting to the needs of 4K coding with higher compression ratios, faster processing speeds and better adaptability.
    • Although HEVC coding technology is not yet fully mature in China, and there is a gap with the self-developed AVS coding, its promotion and development need to be further strengthened.
    • The x265 Testbed is an open source and free software-capable video library compliant with the HEVC/H.265 video coding standard, similar to the x264 project, licensed under the GNU General Public License (GPL) 2 license or a commercial license.

Experimentation and Analysis

A. Introduction to the experiment

  • 实验目的：测试和比较H.264和HEVC（H.265）The encoder is encoding4KPerformance during UHD video sequences。
  • Experimental platforms: Using x264 and x265 testbeds, corresponding to H.264 and HEVC encodings, respectively.
  • Code Setting: Both encoders use a preset system with eight encoding configurations based on encoding rates from ultra-fast to very slow.
  • Experimental equipment: Configurations include a 2.60 GHz Intel Xeon processor, 32 GB of RAM, a 64-bit CPU, and Windows 7 Professional operating system.
  • test sequence: Eight different 4K ultra-high resolution video sequences recommended by ITU-R BT.500 were selected, all with a frame rate of 50.

B. Test rate selection

  • current standard: 4K live channels have been adopted in many countries and regions, with 4K video transmission bit rates set at about 40 Mbps for H.264 encoding and about 20 Mbps for HEVC encoding.
  • Experimental setup: The HD video transmission rate range in the experiment is 20-60 Mbps for H.264 coding and 15-40 Mbps for HEVC coding, and six test points are selected for each rate range.
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C. Analysis of experimental data and results

  1. Experiment 1: Optimal encoding rate test for x264 and x265 encoded 4K sequences.
    • Video Complexity Analysis: The complexity of a video sequence is evaluated by calculating inter-frame differences and edge detection using the TISI complexity assessment method proposed in ITU-R BT.1788.
    • Test Sequence Selection: High-complexity lupo_confetti and medium-complexity studio_dancer were selected for testing based on complexity analysis.
    • Analysis of results: The experimental results show that the coding performance of x265 is slightly better than that of x264 at different bit rates, and x265 is more suitable for 4K sequence coding.
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  2. Experiment 2: Comparison of x264 and x265 encoding performance.
    • performance comparison: At their respective optimal encoding speeds, x265 exhibits better encoding performance than x264, with x265 saving nearly 50% of the bitrate for the same encoding quality.
    • Encoding Time Comparison: Under their respective optimal encoding conditions, x265 takes 50-100 times longer to encode than x264. Under the same conditions (bitrate 35M, medium encoding speed), the encoding time of x265 is about 2-3 times that of x264.
    • Comparison of subjective image quality: The image quality of x265 encoding is significantly better than x264.
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Results

  • Both x264 and x265 have their own optimal encoding speeds, but x265 is better suited for 4K video encoding and outperforms x264 for the same encoding quality at the cost of longer encoding times.

reach a verdict

  1. Optimal encoding speed: x264 and x265 each have an optimal encoding speed. For x264, the optimal encoding speed is the faster level; for x265, the optimal encoding speed is the very slow level.

  2. Relationship between encoding speed and quality: x265 conforms to the encoding rule that the slower the encoding speed, the better the encoding quality.

  3. 4K encoding applicability: x265 is more suitable for encoding 4K video than x264.

  4. Coding Performance Comparison: x265 outperforms x264 for the same encoding quality and saves nearly 50% of the bitrate.

  5. encoding time: Under the same conditions, the encoding time of x265 increases by a factor of 2 to 3 compared to x264.

  6. Coding quality vs. time trade-offs: While x265 provides better encoding quality, this comes at the cost of increased encoding time.