When Apple added HEVC to HLS in June 2017, many predicted it would open the floodgates of HEVC adoption. This
hasn’t happened. You can find some clues as
to why in the Harmonic-sponsored report entitled “The Impact of Apple’s HEVC Adoption: A
Survey-Based Report” ( go2sm.com/harmonic
report). Specifically, when asked about potential concerns regarding implementing HEVC
in HLS, the majority of respondents mentioned
content royalties, compatibility issues, and the
ability to create one set of HEVC-encoded content to deliver to all HLS end points.
We can’t help on the royalty issue; unlike
the MPEG LA and HEVC Advance patent pools,
which won’t charge royalties for HEVC-encoded
streaming videos, the “brain trust” at Velos Media, the third HEVC royalty pool, has obstinately resisted providing similar clarification. On
the other two concerns, we can provide a bit
Here’s the back story: To prepare for a workshop at Streaming Media East on producing HLS
with HEVC, I created two encoding ladders that
combined HEVC and H.264 content. One implemented Apple’s complete recommendation,
which calls for complete duplicate H.264 and
HEVC ladders. The other ladder used H.264 for
low-resolution files (through 540p) and HEVC for
high-res (720p through 4K).
I created the files using a combination of FFmpeg and the open source tool Bento4. Using
a feature in FFmpeg, I burned the codec, resolution, and data rate into each file so you could
tell exactly which file was playing within the
adaptive group at all times. Initially, I hosted the
files on a normal web server, but later Akamai
agreed to host the files on its content delivery
network to ensure that delivery issues weren’t
I posted links to the two HLS presentations
in a LinkedIn article entitled “Please Help Me
Test HEVC Playback in HLS” ( go2sm.com/hevc
test). In the article, I asked readers to test the
streams on a variety of Apple devices and re-
port their results to me. As an incentive, I prom-
ised to send all testers a summary report and
instructions on how they could duplicate my test
files using FFmpeg and Bento4. All told, readers
sent reports from tests on more than 60 test de-
vices—not as many as I would have liked, but
certainly more than I could have tested myself.
What did we learn? First, performance and
compatibility were excellent. There were no
reports of any disruption when switching from
H.264 to HEVC streams, or vice versa. Older devices that were incompatible with HEVC simply
played the H.264 streams.
Another interesting finding was that, in most
cases, the Apple endpoints wouldn’t retrieve
a file larger than the vertical resolution of the
display device. So the largest resolution I could
play on my MacBook Air was 720p, even though
I had the bandwidth to play the 4K streams.
This makes perfect sense, and probably existed all along, but without the burned-in file descriptions, it was just difficult to tell.
One anomaly was that 2K/4K files were very
seldom retrieved, even on devices that had
both the resolution to display the video and the
bandwidth to retrieve them. This is one reason
we asked Akamai to host the videos. An Apple
representative was one of our testers, and Apple is looking into this.
What did we learn about the two ladders?
There were several instances where a device
retrieved a different maximum quality file from
the two encoding ladders, like 1080p HEVC from
the complete ladder, and 360p from the split ladder. But these findings weren’t consistent, so I’m
hesitant to make any firm conclusions without
This is where you come in. The files are still
up in the LinkedIn article, along with instructions on how to test and what information to
send. Send me test results and I’ll send you the
instructions on how to reproduce my test files.
One thing I think everyone involved learned
is that burning the codec, resolution, and data
rate into the files provided a clarity simply unavailable without this data. FFmpeg provides a
simple way to do this, and my article will help
you utilize it in your own testing.
Jan Ozer ( email@example.com) is a streaming
media producer and consultant, a frequent contributor to
industry magazines and websites on streaming-related topics,
and the author of Video Encoding by the Numbers. He blogs
frequently at streaminglearningcenter.com.
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