SILK has been superseded by Opus. Please see Skype's blog post.
This is a modified version of the SILK 1.0.8 codec with optimized ARM/NEON assembly. Compiling and running SILK turned out to be quite a hassle, so I decided to distribute the results of my work here. Note that this is really just a quick&dirty thing, I will not be able to provide any kind of support or help about this.
This code does not compile as 64 bit ARM, at least not the optimized assembly version. I haven't investigated why, but I believe it's simply because there is no 64 bit ARM assembly implementation. There will probably never be one either; SILK has been superseded by Opus. Please see Skype's blog post..
For more information regarding patents, see Skype's SILK website
The easiest way to use this code is to simply add all source files to the Xcode project. It should compile and run happily. It is also possible to create a static library file using the Makefile, but that's more of a hassle, and will probably not work out of the box.
Here are a couple of the things I found out in the process of trying to compile SILK:
http://gcc.gnu.org/ml/gcc-patches/2005-08/msg00565.html For complaints about a missing __aeabi_idiv, it can be replaced with __divsi3. __aeabi_idiv comes from libgcc, and can't be used when using Clang.
For complaints about that arguments ought to be registries, that's a macro issue. Manually expanding those macros solves those errors.
The Makefile has to be edited rather heavily to work. The main things that have to be done are to replace $CC, $CXX, $AR and $RANLIB to be like this:
CC = `xcrun -sdk ${IPHONE_SDK} -find clang`
[etc]
where
IPHONE_SDK = /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS5.1.sdk
I also added this:
CFLAGS += -arch armv7 -mthumb -isysroot ${IPHONE_SDK}
LDFLAGS += -arch armv7 -mthumb -isysroot ${IPHONE_SDK}
USE_NEON=yes
In addition to that, I had to short-circuit the if clause that looks like this:
ifneq (,$(TOOLCHAIN_PREFIX))
Otherwise the assembly files wouldn't get compiled.
There were also 4 byte align warnings from ld about the assembly-defined functions. At first, I ignored them, but then I got illegal instruction errors. These were fixed by adding a ".align 2" line before the ".globl" line.