H.265, also known as HEVC (High Efficiency Video Coding), is a video compression standard developed as a successor to H.264/AVC. Its primary goal is to deliver similar or even better video quality at half the bit rate of H.264, thus offering significant improvements in compression efficiency. Here’s a detailed overview of H.265:
Design Purpose: H.265 was developed to address the increasing demand for higher resolution video (like 4K and 8K) while using less bandwidth. This makes it particularly suitable for streaming high-definition videos over the internet.
Compression Techniques:
- Larger Block Structures: Unlike H.264, which uses a macroblock structure up to 16×16 pixels, H.265 uses Coding Tree Units (CTUs) that can be as large as 64×64 pixels. This allows for better efficiency in representing larger regions of similar data.
- Improved Intra Prediction: H.265 offers 33 directional modes for intra prediction, compared to the 9 in H.264, providing better prediction accuracy.
- Parallel Processing: H.265 is designed to utilize parallel processing techniques, making encoding and decoding processes more efficient on modern multi-core processors.
- Improved Motion Vector Prediction and Precision: This aids in better inter prediction.
- Entropy Coding: H.265 uses only CABAC (Context Adaptive Binary Arithmetic Coding) for entropy coding, which is more efficient than CAVLC used in H.264.
Profiles and Levels: Like its predecessor, H.265 defines several profiles catering to different classes of applications, and levels that set maximum parameters for those profiles.
Network Adaptability: H.265 provides better error recovery features, making it more resilient in environments with packet loss, such as streaming over the internet.
Applications: H.265 is increasingly being adopted for:
- Streaming services (especially for 4K and 8K content)
- Broadcast
- Video storage solutions
- Video conferencing
Licensing: Licensing for H.265 has been more complex than H.264 due to multiple patent pools and licensors. This has been a factor in the adoption rate of H.265 in certain scenarios.
Competition and Alternatives: Other codecs, such as AV1, aim to provide similar or better compression efficiencies as H.265 without the associated patent royalty costs. AV1 is being promoted as a royalty-free alternative, gaining traction, especially in web-based streaming.
In summary, H.265/HEVC represents a significant advancement in video codec technology, offering superior compression efficiency, especially for high-resolution videos. Its adoption rate, however, has been influenced by licensing complexities and the emergence of alternative codecs.