HEVC Wavefront Animation

This is what HEVC wavefront parallel processing looks like in slow motion.

Here is shown a 768x448 single-slice-segment intra-coded picture with entropy_coding_sync_enabled_flag set. The animation shows how a multithreaded decoder or encoder might progress through the frame. Note particularly the following:

• Decoding progresses along each 64x64 CTU row.
• Each CTU changes from dark grey to light grey when its above and above-right neighbour CTU dependencies become available.
• There are four threads active, each working on a different CTU row.
• Within each CTU, decoding walks the quad-tree structure of CUs.
• A CU is shown semi-opaque while it is being processed and when done, the picture appears.
• Complex picture regions such as the trees are decoded more slowly. These parts have higher bit density and smaller CUs.

An experimental four-thread HEVC parser was used to derive the timing information used here. So this does represent real-world timings.

Please feel free to share and show this to others - we hope it helps people understand HEVC and WPP. This visualisation is licensed under a Creative Commons Attribution-NoDerivatives 4.0 International License. The source image is CC licensed too, so please also attribute the photographer, rayandbee.