After reconstructing a frame, the decoder applies an adaptive filter along 4×4 block edges. It measures the difference across the edge and the quantization strength. If the edge is likely due to blocking (not real image detail), it smooths just enough to remove the artifact without blurring true edges.
| Profile | Key features | Typical use | |---------|--------------|--------------| | | No B-slices, no CABAC | Video conferencing, low-delay | | Main | I/P/B slices, CABAC, deblocking | Broadcast, SDTV | | High | 8x8 DCT, perceptual quantization, custom quant matrices | Blu-ray, HD streaming | | High 10 | 10-bit depth | Professional post-production | | High 4:2:2 / 4:4:4 | Chroma subsampling preservation | Archival, medical imaging | anniversary h264
(1 through 5.2) define max resolution, bitrate, and buffer size. Level 3.1 = 720p30. Level 4.1 = 1080p30/1080i60. Level 5.1 = 4K. The Silicon Lottery: Why Hardware Decoding Won MPEG-2 had hardware decoders, but they were expensive. H.264's complexity (up to 400+ operations per pixel vs 60 for MPEG-2) threatened to kill software decoding on 2003-era CPUs. After reconstructing a frame, the decoder applies an
When future archaeologists decode the first two decades of online video, they'll find H.264's start codes ( 0x00 0x00 0x01 ) embedded in more files than any other binary signature. That's the mark of a true standard. | Profile | Key features | Typical use