I've no knowledge of this kind of stuff but what's the big difference between h265 and VP9?
More generally, h265 and VP9 can be seen as competitors in the same space, but with some meaningful differences in philosophy. VP9 is a royalty-free codec developed by Google. The VPx series of codecs all stem from the work of the On2 company, which Google acquired specifically so that it could get into the video codec space.
h265 is patent-protected by a number of parties who are chilling the adoption and rollout of this new codec. As a result, VP9 has seen some rapid adoption by both hardware and software manufacturers lately. If you work in digital video today, the likelihood is that you will need to support both codecs in your processing stack and delivery pipelines.
Other interesting developments in this space include the Daala codec in development by the Xiph Foundation (responsible for Ogg Vorbis, Theora, and the wonderful Opus audio codec) and the Thor codec in development by Cisco and their tech partners. Both are aiming to be next-generation royalty-free codecs for distribution of even smaller, and even prettier videos.
Just about everyone onboard, including hardware manufacturers, patent unencumbered, free, and looks to be a very capable format.
So what are some of the downsides? What are some of its issues?
It's easy to project hopes into something that doesn't exist yet. But this contender is coming late.
I have to disagree, first off, it's not as if we've seen a massive shift over to HEVC, in fact the x265 developers lamented this quite recently, mainly blaming the licensing debacle which has ensued, with three different entities with which you need to negotiate royalties in order to use HEVC (MPEGLA, HEVC Advance, Technicolor), and the royalties were already much more expensive than h264 to begin with.
Secondly, it's quite clear that AV1 will happen, Google was already committed in creating a royalty free codec as evident by their VPX series of codecs, and now they have been joined by web and tech giants like Netflix, Microsoft, Amazon, Cisco, Mozilla, Intel, ARM, NVidia, AMD etc.
For these players, a royalty free codec makes perfect sense, the streaming giants know full and well that they will only increase the amount of video they stream and thus will save money longterm by pooling their resources and creating a royalty free codec, and on the hardware side, not having to pay royalties in order to implement hardware support is obviously attractive.
And it does exist, it's in full development, not something in the 'planning stage', the bitstream is said to be finalized at the end of this year or at the beginning of next, so we are not talking 'many years into the future' here, it's based off VP10 and is adopting techniques from Daala and also have access to h264 patented techniques courtesy of Cisco.
As I see it, HEVC is in a bad situation, h264 is still good enough and much cheaper to license, and within a year we will likely have AV1 ready to go for hardware, why would you jump on the HEVC bandwagon at this point ?
My best suggestion would be to just stick with h264 and see how the HEVC/AV1 situation plays out.
The bad news is that AV1 is still under development and will be for a while yet