x265 – a multithreaded hevc encoder


A new HEVC encoder has been released by MulticoreWare – the x265 encoder.

This tool is not being directly developed by the x264 developers, but they have tentatively thrown their support behind it as it should remain open source software.  Discussion about its release and development can be found on the Doom9 forums.

Tom’s Hardware has also done an early evaluation of the speed/psnr of this release.  They claim it encodes at 4 fps on a Core i5 processor – quite a bit faster than the reference encoder.  However it doesn’t offer near as many options for encoding as the reference encoder and only uses a simple GoP with 4 reference frames using P-frames – I would guess this is just the standard encoder_lowdelay_main.cfg we’ve tested with before.  It does produce good results, but it kind of stinks to be locked into it without the ability to tinker.

I haven’t done a full encode with this alpha yet but I have uploaded a copy of the program along with the release notes: x265 alpha release.

Some things to note are that it seems x265.exe automatically sets IDR to output a closed GoP – so seeking will work fine in these files.  It also has an option to set ‘–gops’ whereby you can set the number of GoPs to encode concurrently, which is essentially the exact same thing we did previously with the reference encoder by cutting our source into individual GoPs.  It’s just much more convenient here!