With its goal to achieve high coding efficiency, e.g., two times compared with H.264, H.265 features include
- 2-D non-separable adaptive interpolation filter (AIF)
- Separable adaptive interpolation filter
- Directional adaptive interpolation filter
- "Super macroblock" structure up to 64x64 with additional transforms
- Large transform block sizes (up to 32x32)
- Adaptive prediction error coding (APEC) in spatial and frequency domain
- Adaptive quantization matrix selection (AQMS)
- Competition-based scheme for motion vector selection and coding
- Mode-dependent KLT for intra coding
- Tree-structured prediction and residual difference block segmentation
- High-accuracy motion compensation interpolation (8 taps)
it was concluded that the preliminary requirements for HEVC (H.265, or H.NGVC) were bit rate reduction of 50% at the same subjective image quality comparing to H.264/MPEG-4 AVC High profile, with computational complexity ranging from 1/2 to 3 times that of the High profile. HEVC (H.265) would be able to provide 25% bit rate reduction along with 50% reduction in complexity at the same perceived video quality as the High profile, or to provide greater bit rate reduction with somewhat higher complexity.
the conclusion showed H.265 can achieve 50% reduction of bit rate at the same PSNR and SSIM as x.264.