
H265: Technical Overview - tambourine_man
https://sonnati.wordpress.com/2014/06/20/h265-part-i-technical-overview/
======
ryuuchin
It'll be interesting to see the adoption rate of h265/HEVC and whether it will
actually take off since the licensing costs seem to be prohibitively
expensive[1].

AV1 may wind up being the defacto winner because of this even if it means we
have to wait longer before any transition occurs. We may wind up sticking to
h264 and VP9 longer despite hardware already shipping with h265/HEVC support.

[1] [https://yro.slashdot.org/story/15/07/26/0149234/hevc-
advance...](https://yro.slashdot.org/story/15/07/26/0149234/hevc-advance-
announces-h265-royalty-rates-raises-some-hackles)

~~~
revelation
It has taken off among pirates alright.

(There is a noticeable battery life penalty for h265 content though)

~~~
IntelMiner
I thought H265 was banned among most private trackers?

I know my private releases to friends are all H265, though they all use
hardware that has native decoding (or is beefy enough to transcode from)

~~~
drakenot
How common are native h265 decoders now? I've been curious when we would start
to see stronger hardware support.

~~~
dylan604
Most Samsung phones can do it. I know at least as early as the Note 4. HEVC is
codec of choice for 360 video for the Gear environment due to its small file
size. The Galaxy S7 can do 4K60 in HEVC. Although, VLC has a hard time playing
these files on beefy PCs used to encode these files. My 4K/UHD LG SmartTV
running WebOS from 2013/14 plays HEVC as well. The Netflix app handles their
4K streams with no problem.

There are just personal first hand knowledge examples.

------
hd4
While we're discussing codecs that effectively obsolete the ones that came
before, I thought I should mention the absolutely incredible Opus codec, which
is interestingly based partly off the Skype codec. Basically you get
equivalent quality to 'other' audio codecs but using up half the space.

[http://opus-codec.org/](http://opus-codec.org/)

~~~
LeoPanthera
Opus is so much better than any lossy audio codec that came before that I
wonder if it will be the "ultimate" audio codec. I'm sure minor improvements
will continue to be made but it does feel like we're pushing the limits of
lossy compression at this point.

------
IshKebab
Funny how interesting comments always end up on the front page a day or two
later. Happens on Reddit all the time too.

This one is because of this comment:
[https://news.ycombinator.com/item?id=12872108](https://news.ycombinator.com/item?id=12872108)

------
userbinator
The massive increase in the number of choices the encoder has to make (and
correspondingly, the decoder to follow) is the main reason why H.265 requires
so much more processing power than H.264, and H.264 compared to previous
standards as well. The intra prediction modes (33 directions!) are a good
example of this.

That said, if you actually get the standard and look at the section on the
intra prediction modes, how to compute them is spelled out in very detailed
pseudocode.

~~~
baybreeze
Also expensive is using CABAC, which is much slower (for better compression
ratio). H.264 allowed used a faster coder called CAVLC.

There are two ways to interpret this: either low-powered devices have become
much stronger, or h.264 is just not supporting some classes of devices.

~~~
ryuuchin
I believe CABAC in h265/HEVC should be faster than CABAC in h264/AVC. If you
produced CABAC for h264 and h265 with all things being equal you should
actually gain in decoding speed moving to h265.

------
adilparvez
Another technical overview:
[http://forum.doom9.org/showthread.php?t=167081](http://forum.doom9.org/showthread.php?t=167081)

Edit: Just realised IshKebab linked to my comment linking to doom9 in
yesterday's h264 thread.

~~~
rb2k_
Off topic, but:

Really nice to seem doom9 mentioned. Doom9 is one of those places that I used
to frequent a lot. That knowledge saved me a lot of learning in university :)

Sadly also one of those places where I forgot both the password to my account
and the gmx email doesn't exist anymore. It's a shame, the account is from
2001.

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uabstraction
This was a very fascinating writeup. Video codecs are still sorcery to me, but
I was kind of blown away by how many individual operations are employed in
shedding redundancy. I kind of assumed that there was a single flat algorithm
being employed, not a dozen or so special case optimizations that by some
stroke of magic play so nicely together.

~~~
mbebenita
If you're curious about this sort of thing, you can play with
[http://aomanalyzer.org/](http://aomanalyzer.org/) which is a tool that lets
you inspect AV1 (AOM/VP9) bit streams.

------
takdi
I've no knowledge of this kind of stuff but what's the big difference between
h265 and VP9?

~~~
AndrewUnmuted
On the technology side of things, h265 and VP9 are both attempting to further
increase compression efficiency so that we can deliver super high resolutions,
wide color gamuts, and bit depths greater than 8. These features are very
difficult to achieve with wide compatibility when utilizing h264 and VP8.

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.

~~~
mikevm
It is also important to mention AV1
([https://en.wikipedia.org/wiki/AOMedia_Video_1](https://en.wikipedia.org/wiki/AOMedia_Video_1))
which is meant to replace VP9 and compete against H.265.

~~~
Klathmon
Looking at AV1, it looks almost too good to be true.

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?

~~~
Strom
One issue is that it's a prototype with planned future greatness. It's tricky
to reach H265 compression ratio without touching patented methods. Even if
they reach it, by that time H265 will probably have well-optimized
encoders/decoders, so there will be major speed differences. Still a worthy
effort of course.

~~~
p0nce
H.265 already has realtime 4kp60 10-bit encoder boxes out there, multiple
hardware decoder and encoder IPs. This race started back in 2012 or earlier.
Existing chips in consumer devices trounces every H.264 encoder out there:
[http://compression.ru/video/codec_comparison/hevc_2016/MSU_H...](http://compression.ru/video/codec_comparison/hevc_2016/MSU_HEVC_comparison_2016_free.pdf)
Which is not the case for any encoder of VPx ascent.

It's easy to project hopes into something that doesn't exist yet. But this
contender is coming late.

~~~
TD-Linux
Afaik every phone made in the last year has a VP9 hardware decoder.

~~~
sroussey
I know the iPhone 6, 6s, and 7 all have hardware h.265, and use it for
FaceTime for example for many years. I can not locate evidence that they have
VP9.

------
shmerl
I hope it won't get a wide adoption of H.264. We need free codec alternative,
instead of locking everyone into this closed / patented codec for years to
come.

What's the story with Daala + Thor aka NETVC and Alliance for Open Media
plans? When do they plan to make their codec production ready?

~~~
kimburgess
They are targeting having the format frozen by March 2017.

[http://www.streamingmedia.com/Articles/Editorial/Featured-
Ar...](http://www.streamingmedia.com/Articles/Editorial/Featured-
Articles/A-Progress-Report-The-Alliance-for-Open-Media-and-the-
AV1-Codec-110383.aspx)

~~~
shmerl
_> So how will contributions from Google’s VP10, Mozilla’s Daala, or Cisco’s
Thor be represented in AV1? Gabe Frost explained, “The baseline code in the
AV1 project represents where the lion’s share of investment came from before
the investment,” essentially indicating that code from VP10, by far the most
mature of the three, will dominate. Frost indicated that AV1 will contain some
of the best ideas and features of both Daala and Thor._

So will Mozilla continuing developing Daala? And what about NETVC? How does it
correlate to AV1?

~~~
wyoh
Daala will continue to be developed but as a research testbed.

~~~
shmerl
Does it mean they didn't manage to advance Daala to needed quality to make it
production ready?

~~~
wyoh
I don't think so, if we are to believe arewecompressedyet.com, Daala is on par
with x265 quality-wise. But they are now sharing their technologies to make
Alliance for Open Media's AV1, the next gen patent free codec. They've been
talks about using Daala as a still image codec but I don't know if it's gonna
happen or not.

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nazka
It's totally random but I read a paper in ML with the same kind of
decomposition for the picture. Does someone know it by some chance? I think it
was linked to group theory.

~~~
santaclaus
Is anything _not_ linked to group theory?

~~~
nazka
Ya I just have a few memories of it. Sorry I can't help much... Thank you
though.

------
nom
Can someone here estimate how valuable modern video codecs are? Everybody
needs them but development is super expensive and requires many bright minds.

~~~
olegkikin
Extremely valuable. Most of the traffic on the web is video. Youtube / NetFlix
/ torrents / porn.

H265/HEVC lets you halve the traffic while keeping the quality the same.
That's a big deal.

