Hi there,
I took a look at the AOSP libjpeg code which is included in
git://android.git.kernel.org/platform/external/jpeg
during my flight back home (which incidentally had been diverted and
landed me in Rio de Janeiro; not sure if I celebrate or cry) and noted
the following things:
- There is a v6 implementation of the fast IDCT algorithm which
lives in armv6_idct.S.
- The commit which adds this implementation was added October 2010,
and there haven't been any changes since.
- The code that selects the decoder IDCT implementation in
jddctmgr.c always uses that implementation if ANDROID_ARMV6_IDCT
is defined.
- Google have an "ashmem" backing store implementation, and have
code to enable tile-based mode. It's a fairly non-intrusive change
to use ashmem since it just replaces jpeg_open_backing_store.
- The code is pretty much standard libjpeg without any structural
changes to it.
- There isn't any NEON code in this branch.
- Mans has an optimized version here:
http://git.mansr.com/?p=libjpeg;a=summary
I don't know if he's submitted this to AOSP or not.
This suggests to me that a simple drop-in of libjpeg-turbo might be
actually easy to do, and that there is probably a significant
performance benefit to be achieved. One thing to keep in mind is that
this code still supports armv6, so we'd probably want to preserve that.
Thanks!
--
Christian Robottom Reis, Engineering VP
Brazil (GMT-3) | [+55] 16 9112 6430 | [+1] 612 216 4935
Linaro.org: Open Source Software for ARM SoCs
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