[Libav-user] question about libavcodec

卜弋天 buyit at live.cn
Sun Feb 26 15:19:38 CET 2012

Hi experts:
    i have some questions about the libavcodec.so: 
    1. when compiling, how can i specify this library is compiled for ARM? and it includes NEON instruction supports? 
    2. suppose ARCH_ARM and HAVE_NEON are defined, which i mentioned in question 1, does it mean this library can only be executed on ARM platform and the chipset must have NEON module? 
    3. suppose the answer of quesion 2 is yes, then how can user choose libavcodec.so as they want? for example, there is an Android application "ROAMSAVE", it will use libavcodec.so, then how can i choose a suitable version libavcodec.so for roamsave? suppose i do not have any source code, and just want to download this library from internet?
    4. if the application roamsave together with a specific libavcodec run well on Samsung smart phone, and i am sure this version libavcodec support ARM and execute NEON instruction. but when i use them on another smart phone(Motorola), it crashs in libavcodec.so, the problem is alignment of second parameter of function ff_scalarproduct_int16_neon(), how can i find the root cause?the libavcodec runs NEON instruction well on Samsumg phone, so it means this library compiled with correct GCC version and can handle stack alignment well , right? but why it crashs because of alignment problem when run on another smart phone which also support NEON instruction? i am very confused about this issue, please help me, thanks very much.  
Best Regards  		 	   		  
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