[FFmpeg-devel] [PATCH 4/6] truehd: tune VLC decoding for ARM.

[Ben Avison]

On Thu, 20 Mar 2014 06:45:13 -0000, Reimar Döffinger <Reimar.Doeffinger at gmx.de> wrote:
> This sounds to me like cache-tuning.
> The Raspberry Pi CPU is really tiny, calling it "optimize for ARM"
> seems like a misleading title.
> There is a good chance that with larger implementations the original
> values _might_ be faster, just like the smaller ones might be better
> with e.g. x86 Atoms.

It's true, it's very much a first approximation to base it on the
architecture. But ARMs do tend to - on average - have smaller caches than
x86, for example.

It's worth noting that the VLC code is used by many other codecs, and so
there's a lot of potential for tuning them as well, although the exact
best choice will depend not only upon the precise CPU used, but also on
the test clips being profiled (for example due to the interaction with
other codecs present). So it's always going to be tricky to define what
the best setting is, especially when the build system isn't really set up
to allow tuning for a specific CPU (as far as I'm aware).

Ben