[Libav-user] question about libavcodec

Sheldon Qu quyadong at hotmail.com
Tue Feb 28 14:00:08 CET 2012

From: ²·ß®Ìì 
Sent: Monday, February 27, 2012 5:33 PM
To: libav-user at ffmpeg.org 
Subject: Re: [Libav-user] question about libavcodec

Hi Experts:
    plase help, thanks very much.
Best Regards

From: buyit at live.cn
To: libav-user at ffmpeg.org
Subject: question about libavcodec
Date: Sun, 26 Feb 2012 22:19:38 +0800

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? 
run configure ¨Chelp or search in google
    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?
ask your mentor
    4. if the appl ication 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.
recompile for motor and try it again.
Best Regards 

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