[Libav-user] Build tag n2.4 for armv7 with --disable-armv6 complaints link error

Carl Eugen Hoyos cehoyos at ag.or.at
Fri Sep 19 13:26:43 CEST 2014

Zhang Rui <bbcallen at ...> writes:

> 2014-09-19 5:31 GMT+08:00 Carl Eugen Hoyos <cehoyos at ...>:
> > First and most important:
> > Why are you using --enable-pic?
> > I have heard different opinions, did you do any
> > benchmarks? Is there anything that does not work
> > without it?
> > Should it be the default for iOS in your opinion?
> I have no idea.

Does it work at all for you without --enable-pic?
Can you do a performance test?


> > (But see below for --disable-all, you will have to add
> > all --enable options except avutil then.)
> There is not ./configure --list-all to announce which options excatly
> effected by --disable-all

But there is the output of ./configure --disable-all

--disable-everything is - no matter its name - a 
debug option for developers to speed up compilation, 
--disable-all disables all features that can be 
disabled except default library features. configure 
output will tell you more.

> I don't think I have enough knowledge to handle every options,

One more reason to use --enable-all instead of a 
very complicated configure line.

> I only set what I expect and leave others as default value.

This is not how I read your current configure line...

> I thought --disable-all could disable some options I 
> don't expect to be disabled by chance.

You already disable all possible options in your current 
configure line afaict.


> >> --disable-dxva2 --disable-vaapi --disable-vda
> >> --disable-vdpau
> >
> > dxva2, vaapi and vdpau cannot be enabled for iOS, if vda
> > would work, I suspect you would want it or not?
> I'm afraid vda API only works on OS X, but not on iOS in normal way.

That is what I meant above:
You don't need the options because they don't 
disable anything.
If --disable-vda would do anything useful, you 
would not want to use it (I guess).

> FYI. There is a VideoToolBox api on iOS, which was 
> private API, and is released as public API on iOS8.

Who are you telling...


> >> --disable-armv5te --disable-armv6
> >> --disable-armv6t2 --arch=armv7 --enable-neon
> >
> > Can you explain this?
> > Why are you disabling some optimizations for the
> > arm target? I would have expected that the three
> > disable options are not a good idea. What do I
> > miss?
> > (Removing them would also fix your linking issue
> > I assume.)
> I thought armv6 optimizations have nothing to do with armv7.
> I've seen something in XBMC, like this:
> ifeq ($(findstring arm, $(CPU)), arm)
> ffmpg_config += --enable-pic --disable-armv5te --disable-armv6t2

I suggest you remove  --disable-armv6 from your 
configure line.
(And benchmark h264 if you want.)

Carl Eugen

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