IBC
The video industry will have to learn to juggle
between AV1, H.264, HEVC and VP9 and future codecs like VVC. That’s the lesson
from IBC where warring factions in the codec wars came to trade blows without
landing a palpable hit.
A survey into codec use released on the eve of the show by
developer Bitmovin showed a dramatic surge in the number of users planning to
adopt AV1 in the next 12 months. Some 29% of those surveyed say they will work
with AV1, double the planned usage rate since 2017.
At the same time, planned deployment of HEVC and VP9 are
shown to have decreased, reflecting a trend toward using a wider array of next
generation codecs in the future.
Huge impetus was given to the codec by YouTube’s declaration
during IBC that it is beta testing AV1 with Chrome 70 and Firefox Nightly.
The conundrum is that AV1 isn’t remarkably better in
performance than HEVC, nor are there yet many encoder products to deploy.
Some comparisons of AV1 versus HEVC show subjectively that
one is better than the other but other examples, looking at edge definition for
example, show HEVC outperforming AV1. The results of a BBC R&D study
released at IBC showed the compression capabilities of both are similar.
“It’s a close call between them,” said Ateme consultant Ian
Trow. “I won’t pretend to be the judge.”
Most experts seem to agree that AV1 is an improvement over
HEVC but on a far more modest scale than the leaps made between predecessor
standards.
So how to explain AV1’s sudden rise? AV1 was only launched
in March of 2018, as the royalty free codec from the Alliance for Open Media
(AOMedia) and endorsed by all major device manufacturers, browser vendors, and
content distributors including Netflix. Driven by engineering teams at browser
makers and content distributors like Google, Mozilla, Microsoft, Facebook and
others, Bitmovin suggest AV1 is clearly gaining momentum.
“Already Firefox, Chrome and Edge Web browsers support AV1
in their early release versions, which suggests commercial applications are
just around the corner,” it says. “This explains the importance of AV1 for a
lot of developers.”
Video streamers are used to royalty free licencing and it’s
thought likely that AV1 will take over from H.264 AVC in this area. A
royalty-free license could translate into tangible operating-cost savings for
YouTube and other video streaming services.
File based downloads will likely be the first wave of AV1
application. “There is significant momentum on that,” said McCann. “I have no
doubt that live low latency OTT is key for AV1 but it will be its second phase
of development.”
AV1 adoption also benefits from the licencing mess which the
HEVC patent holders have got themselves into.
“Let’s not delude ourselves, the rights and royalty maze of
HEVC has added to AV1’s acceleration,” said Trow.
Ken McCann, founder at consultants Zetacast said that in
informal discussions among HEVC patent holders “there was now consensus that
there is a problem. But there’s no consensus about the solution.”
However, the apparent complexity of AV1 is an issue,
especially when handling the higher bit rates required for 4K and 8K
sport. BBC R&D’s video coding researcher Andre Dias referred to the
extensive processing demands, significant run time, footprint and power needs
of AV1.
“As for complexity, decoding times of HEVC are significantly
lower than for other tested solutions, while the encoding complexity of AV1 is
much higher than the other tested codecs,” he explained.
“Royalties are nothing alongside transcoding costs in this
instance,” noted one IBC attendee who preferred to remain anonymous.
As practical AV1 implementations get more and more mature,
it is expected that faster implementations can reach realistic encoding times,
“ideally without significantly compromising the compression performance
provided by this specification,” added Dias.
BBC R&D is hedging its bets. It is a member of the HEVC
development team and has refined its own software implementation called the
Turing Codec, optimised for UHD. BBC R&D also supports AOMedia and is fully
onboard with VVC, the next-gen codec being developed by a combined MPEG/ITU
team called JVET.
The VVC standard is expected to complement emerging delivery
protocols and networks, such as 5G, enabling the delivery of higher quality
video services such as high frame rate and 360-video.
“The work being carried out in JVET [on VVC] seems to
outperform both HEVC and AV1, proving that higher compression efficiency can be
achieved and that the VVC standard will be able to deliver substantial coding
advantages over available solutions,” reported Dias.
None of this should detract from the current domination of
video codec usage by incumbent H.264/AVC. However, H.265/ HEVC has expanded
rapidly, up from less than a third (28%) of usage in 2017. According to
Bitmovin this indicates developers are working with both codecs simultaneously.
Developments in content aware encoding can be applied over
the top of either HEVC or AV1 to further refine compression performance.
Technologies like V-Nova’s Perseus can also be used
alongside other codecs including HEVC to improve results. At IBC, V-Nova was
demonstrating both its Perseus Pro codec, which uses intra-only compression
(i.e. exploiting spatial redundancy within individual video frames) and its
Perseus Plus variant, which uses inter-frame compression (also exploiting
temporal redundancy between video frames).
The latter is used for lossless contribution, production and
imaging workflows; while the former adds layers of detail and upscaling on top
of industry-standard codecs like H.264 and HEVC to increase distribution
efficiency to viewers.
One demo showed live encoding and distribution for 50fps 4K
at as little as 8 Mbps “Up to 70% lower bandwidth than other solutions in use
today,” claimed the firm.
“At this this stage there is no truly independent comparison
of Perseus with others,” said Zetacast’s McCann. “We need someone to put
resources into comparison analysis.”
Cisco’s Visual Networking Index reveals by 2021 that 82
percent of all traffic on the Internet will be video. As a result, video
distributors must implement methods to reduce the bitrate of the video they
deliver without compromising quality.
The desire to improve the commercial situation for future
compression standards like VVC, by reassuring potential users that the mistakes
of HEVC will not be repeated, led several industry players to get together and
form the Media Coding Industry Forum (MC-IF).
Launched at IBC, the MC-IF said it would facilitate
cross-industry discussion on non-technical aspects surrounding the deployment
of media standards, notably including licensing.
The initial members include b<>com, Bitmovin,
CableLabs, Canon, Digital Insights, Divideon, Ericsson, Harmonic, HEVC Advance,
InterDigital, MediaKind, NGCodec, Nokia, OP Solutions, Technicolor, Tencent,
Unified Patents, and Zetacast.
No comments:
Post a Comment