[FFmpeg-devel] AAC encoder 3x performance drop in 3.0 since Oct 2014

Ganesh Ajjanagadde gajjanag at gmail.com
Tue Mar 1 03:30:28 CET 2016

On Mon, Feb 22, 2016 at 11:34 PM, Andrey Utkin
<andrey_utkin at fastmail.com> wrote:
> Hi!
> I am aware of news that AAC encoder got stable status recently.
> But you could find this interesting. We've got an ffmpeg build from
> October 2014, and it performs three times faster on AAC encoding than
> recent 3.0 release. There is no complaints about audio quality on old
> version, and I can honestly say the audio quality is really
> satisfiable on old version. The performance is paramount in our
> particular usecase, so it is silly to deploy a new version which
> performs so noticeably worse. Still deploying new release is needed due
> to other particular bugfixes.
> Obvious things like lowering bitrace, setting "-aac_coder fast" don't
> help.
> You can check this yourself with this script (it is also inlined below):
> https://gist.github.com/andrey-utkin/c60cd4070eb962d58075
> On my workstation, the old version finishes the transcoding in 2.5s,
> the new one in 6.6s.
> Is there any workaround? Or is the old times speed is buried by
> correctness and stability?

No idea about this. However, here is some info.
The regression in speed dates to: 01ecb7172b684f1c4b3e748f95c5a9a494ca36ec.
At this commit, there was a bad speed regression (11.475 s, vs 2.525 s
before vs 6.565 s current).
As can be judged from this, since the main commit bringing in the
revamped encoder, there have been efforts that have shaved off some
time, some that increase it slightly, etc.
However, the chief one that brought it down from 11.x to 6.y was
b629c67ddfceb7026e407685f04d1bb09cb08d31. Since then, performance has
been generally stable at ~ 6.5 s +/- 10%.

Generally speaking though, it is indeed true that speed is still
somewhat lacking:

Ideally, FATE should have some basic plotting/performance
infrastructure, e.g a client can submit perf figures so that evolution
over time can be viewed. No idea why this can't be done.
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