Current state on this:
* delaying to mid-July so I don't start a batch process and leave it
unattended for a week :)
* still hoping to deploy the libvpx+ffmpeg backport first so we start with
best performance; Moritz made a start on libvpx but we still have to
resolve ffmpeg (possibly by patching 3.2 instead of updating all the way to
* after further testing of 30fps and 60fps files, I'm also planning to
increase the data rate a bit.
I want to do a little more testing on the ideal data rate, but it'll end up
looking more like a 30% reduction than a 38% reduction in file size. Our
current VP8 and provisional-VP9 configurations were tuned mostly on 24fps
files, while 30fps files are very common and require a moderately higher
data rate to reduce compression artifacts. (50fps and 60fps files are also
around, and will also benefit from an increase in data rate.)
(Possibly the data rate will end up scaled according to frame rate, but
frame rate is surprisingly hard to calculate reliably for WebM input.)
On Sun, Jun 17, 2018 at 1:32 PM Brion Vibber <bvibber(a)wikimedia.org> wrote:
On Sun, Jun 17, 2018 at 12:30 PM Brian Wolff
Good to see us moving forward to newer codecs.
What is the expected impact on transcode
time/memory usage? (As in, will
large videos still transcode fine or would they potentially hit limits
Using the same CPU thread count, typical files take about 3-4 times longer
with the configuration we've got ready. This doesn't seem to be a major
problem at low resolutions, but higher resolutions may need to have the
limits raised for very long videos like conference talks. Memory usage may
be higher but I've not specifically noticed a major difference between VP8
and VP9 there.
This could be improved significantly by updating to libvpx 1.7 and a
matching version of ffmpeg that supports macroblock row multithreading:
this means that we'll be able to use more than 4 threads for HD videos,
which should allow using all cores on a 20-core/40-thread machine if it's
not loaded up with other files.
The necessary libraries are released; we just need to backport the newer
packages to Debian 9 I believe. Don't yet know whether this will be an easy
or hard task.
Now that you mention it I am concerned about the time limit on very long
videos, so I'll take another look at the packaging backport and see if we
can knock that out quickly. :)