问题
I'm following the reference at http://developer.apple.com/iphone/library/qa/qa2010/qa1702.html to capture video from the iPhone camera. It's a fresh project aside from the code from that page. I added the AVFoundation framework to the project as well. Here's the linker errors I get:
Build my project of project my project with configuration Debug
CompileC "build/my project.build/Debug-iphoneos/my project.build/Objects-normal/armv6/MainViewController.o" /Users/mwilliamson/Projects/my_project/iphone/Classes/MainViewController.m normal armv6 objective-c com.apple.compilers.gcc.4_2
cd /Users/mwilliamson/Projects/my_project/iphone
setenv LANG en_US.US-ASCII
setenv PATH "/Developer/Platforms/iPhoneOS.platform/Developer/usr/bin:/Developer/usr/bin:/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin:/usr/X11/bin:/opt/local/bin:/usr/local/git/bin"
/Developer/Platforms/iPhoneOS.platform/Developer/usr/bin/gcc-4.2 -x objective-c -arch armv6 -fmessage-length=0 -pipe -std=c99 -Wno-trigraphs -fpascal-strings -O0 -Wreturn-type -Wunused-variable -isysroot /Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS4.0.sdk -fvisibility=hidden -gdwarf-2 -mthumb -miphoneos-version-min=4.0 -iquote "/Users/mwilliamson/Projects/my_project/iphone/build/my project.build/Debug-iphoneos/my project.build/my project-generated-files.hmap" "-I/Users/mwilliamson/Projects/my_project/iphone/build/my project.build/Debug-iphoneos/my project.build/my project-own-target-headers.hmap" "-I/Users/mwilliamson/Projects/my_project/iphone/build/my project.build/Debug-iphoneos/my project.build/my project-all-target-headers.hmap" -iquote "/Users/mwilliamson/Projects/my_project/iphone/build/my project.build/Debug-iphoneos/my project.build/my project-project-headers.hmap" -F/Users/mwilliamson/Projects/my_project/iphone/build/Debug-iphoneos -I/Users/mwilliamson/Projects/my_project/iphone/build/Debug-iphoneos/include -I/Users/mwilliamson/Projects/my_project/iphone/opencv_device/include "-I/Users/mwilliamson/Projects/my_project/iphone/build/my project.build/Debug-iphoneos/my project.build/DerivedSources/armv6" "-I/Users/mwilliamson/Projects/my_project/iphone/build/my project.build/Debug-iphoneos/my project.build/DerivedSources" -include /var/folders/kW/kW6u6B7SGyGYu+nNumtIa++++TI/-Caches-/com.apple.Xcode.501/SharedPrecompiledHeaders/my_project_Prefix-alujyqxskcuyuogdsynmjyrkxbhh/my_project_Prefix.pch -c /Users/mwilliamson/Projects/my_project/iphone/Classes/MainViewController.m -o "/Users/mwilliamson/Projects/my_project/iphone/build/my project.build/Debug-iphoneos/my project.build/Objects-normal/armv6/MainViewController.o"
/Users/mwilliamson/Projects/my_project/iphone/Classes/MainViewController.m: In function '-[MainViewController captureOutput:didOutputSampleBuffer:fromConnection:]':
/Users/mwilliamson/Projects/my_project/iphone/Classes/MainViewController.m:126: warning: 'MainViewController' may not respond to '-imageFromSampleBuffer:'
/Users/mwilliamson/Projects/my_project/iphone/Classes/MainViewController.m:126: warning: (Messages without a matching method signature
/Users/mwilliamson/Projects/my_project/iphone/Classes/MainViewController.m:126: warning: will be assumed to return 'id' and accept
/Users/mwilliamson/Projects/my_project/iphone/Classes/MainViewController.m:126: warning: '...' as arguments.)
Ld "build/my project.build/Debug-iphoneos/my project.build/Objects-normal/armv6/my project" normal armv6
cd /Users/mwilliamson/Projects/my_project/iphone
setenv IPHONEOS_DEPLOYMENT_TARGET 4.0
setenv PATH "/Developer/Platforms/iPhoneOS.platform/Developer/usr/bin:/Developer/usr/bin:/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin:/usr/X11/bin:/opt/local/bin:/usr/local/git/bin"
/Developer/Platforms/iPhoneOS.platform/Developer/usr/bin/gcc-4.2 -arch armv6 -isysroot /Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS4.0.sdk -L/Users/mwilliamson/Projects/my_project/iphone/build/Debug-iphoneos -F/Users/mwilliamson/Projects/my_project/iphone/build/Debug-iphoneos -filelist "/Users/mwilliamson/Projects/my_project/iphone/build/my project.build/Debug-iphoneos/my project.build/Objects-normal/armv6/my project.LinkFileList" -dead_strip -lz -lstdc++ /Users/mwilliamson/Projects/my_project/iphone/opencv_device/lib/libcxcore.a /Users/mwilliamson/Projects/my_project/iphone/opencv_device/lib/libcv.a -miphoneos-version-min=4.0 -framework Foundation -framework UIKit -framework CoreGraphics -framework AVFoundation -o "/Users/mwilliamson/Projects/my_project/iphone/build/my project.build/Debug-iphoneos/my project.build/Objects-normal/armv6/my project"
Undefined symbols:
"_CVPixelBufferGetBaseAddress", referenced from:
-[MainViewController imageFromSampleBuffer:] in MainViewController.o
"_CVPixelBufferUnlockBaseAddress", referenced from:
-[MainViewController imageFromSampleBuffer:] in MainViewController.o
"_CVPixelBufferLockBaseAddress", referenced from:
-[MainViewController imageFromSampleBuffer:] in MainViewController.o
"_CMSampleBufferGetImageBuffer", referenced from:
-[MainViewController imageFromSampleBuffer:] in MainViewController.o
"_CVPixelBufferGetHeight", referenced from:
-[MainViewController imageFromSampleBuffer:] in MainViewController.o
"_kCVPixelBufferPixelFormatTypeKey", referenced from:
_kCVPixelBufferPixelFormatTypeKey$non_lazy_ptr in MainViewController.o
(maybe you meant: _kCVPixelBufferPixelFormatTypeKey$non_lazy_ptr)
"_CVPixelBufferGetWidth", referenced from:
-[MainViewController imageFromSampleBuffer:] in MainViewController.o
"_CVPixelBufferGetBytesPerRow", referenced from:
-[MainViewController imageFromSampleBuffer:] in MainViewController.o
"_CMTimeMake", referenced from:
-[MainViewController setupCaptureSession] in MainViewController.o
"_CVPixelBufferGetDataSize", referenced from:
-[MainViewController imageFromSampleBuffer:] in MainViewController.o
ld: symbol(s) not found
collect2: ld returned 1 exit status
CompileC "build/my project.build/Debug-iphoneos/my project.build/Objects-normal/armv7/MainViewController.o" /Users/mwilliamson/Projects/my_project/iphone/Classes/MainViewController.m normal armv7 objective-c com.apple.compilers.gcc.4_2
cd /Users/mwilliamson/Projects/my_project/iphone
setenv LANG en_US.US-ASCII
setenv PATH "/Developer/Platforms/iPhoneOS.platform/Developer/usr/bin:/Developer/usr/bin:/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin:/usr/X11/bin:/opt/local/bin:/usr/local/git/bin"
/Developer/Platforms/iPhoneOS.platform/Developer/usr/bin/gcc-4.2 -x objective-c -arch armv7 -fmessage-length=0 -pipe -std=c99 -Wno-trigraphs -fpascal-strings -O0 -Wreturn-type -Wunused-variable -isysroot /Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS4.0.sdk -fvisibility=hidden -gdwarf-2 -mthumb -miphoneos-version-min=4.0 -iquote "/Users/mwilliamson/Projects/my_project/iphone/build/my project.build/Debug-iphoneos/my project.build/my project-generated-files.hmap" "-I/Users/mwilliamson/Projects/my_project/iphone/build/my project.build/Debug-iphoneos/my project.build/my project-own-target-headers.hmap" "-I/Users/mwilliamson/Projects/my_project/iphone/build/my project.build/Debug-iphoneos/my project.build/my project-all-target-headers.hmap" -iquote "/Users/mwilliamson/Projects/my_project/iphone/build/my project.build/Debug-iphoneos/my project.build/my project-project-headers.hmap" -F/Users/mwilliamson/Projects/my_project/iphone/build/Debug-iphoneos -I/Users/mwilliamson/Projects/my_project/iphone/build/Debug-iphoneos/include -I/Users/mwilliamson/Projects/my_project/iphone/opencv_device/include "-I/Users/mwilliamson/Projects/my_project/iphone/build/my project.build/Debug-iphoneos/my project.build/DerivedSources/armv7" "-I/Users/mwilliamson/Projects/my_project/iphone/build/my project.build/Debug-iphoneos/my project.build/DerivedSources" -include /var/folders/kW/kW6u6B7SGyGYu+nNumtIa++++TI/-Caches-/com.apple.Xcode.501/SharedPrecompiledHeaders/my_project_Prefix-gtrotaxhqdjhgqbqbsnyeqjkaxdt/my_project_Prefix.pch -c /Users/mwilliamson/Projects/my_project/iphone/Classes/MainViewController.m -o "/Users/mwilliamson/Projects/my_project/iphone/build/my project.build/Debug-iphoneos/my project.build/Objects-normal/armv7/MainViewController.o"
/Users/mwilliamson/Projects/my_project/iphone/Classes/MainViewController.m: In function '-[MainViewController captureOutput:didOutputSampleBuffer:fromConnection:]':
/Users/mwilliamson/Projects/my_project/iphone/Classes/MainViewController.m:126: warning: 'MainViewController' may not respond to '-imageFromSampleBuffer:'
/Users/mwilliamson/Projects/my_project/iphone/Classes/MainViewController.m:126: warning: (Messages without a matching method signature
/Users/mwilliamson/Projects/my_project/iphone/Classes/MainViewController.m:126: warning: will be assumed to return 'id' and accept
/Users/mwilliamson/Projects/my_project/iphone/Classes/MainViewController.m:126: warning: '...' as arguments.)
Ld "build/my project.build/Debug-iphoneos/my project.build/Objects-normal/armv7/my project" normal armv7
cd /Users/mwilliamson/Projects/my_project/iphone
setenv IPHONEOS_DEPLOYMENT_TARGET 4.0
setenv PATH "/Developer/Platforms/iPhoneOS.platform/Developer/usr/bin:/Developer/usr/bin:/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin:/usr/X11/bin:/opt/local/bin:/usr/local/git/bin"
/Developer/Platforms/iPhoneOS.platform/Developer/usr/bin/gcc-4.2 -arch armv7 -isysroot /Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS4.0.sdk -L/Users/mwilliamson/Projects/my_project/iphone/build/Debug-iphoneos -F/Users/mwilliamson/Projects/my_project/iphone/build/Debug-iphoneos -filelist "/Users/mwilliamson/Projects/my_project/iphone/build/my project.build/Debug-iphoneos/my project.build/Objects-normal/armv7/my project.LinkFileList" -dead_strip -lz -lstdc++ /Users/mwilliamson/Projects/my_project/iphone/opencv_device/lib/libcxcore.a /Users/mwilliamson/Projects/my_project/iphone/opencv_device/lib/libcv.a -miphoneos-version-min=4.0 -framework Foundation -framework UIKit -framework CoreGraphics -framework AVFoundation -o "/Users/mwilliamson/Projects/my_project/iphone/build/my project.build/Debug-iphoneos/my project.build/Objects-normal/armv7/my project"
Undefined symbols:
"_CVPixelBufferGetBaseAddress", referenced from:
-[MainViewController imageFromSampleBuffer:] in MainViewController.o
"_CVPixelBufferUnlockBaseAddress", referenced from:
-[MainViewController imageFromSampleBuffer:] in MainViewController.o
"_CVPixelBufferLockBaseAddress", referenced from:
-[MainViewController imageFromSampleBuffer:] in MainViewController.o
"_CMSampleBufferGetImageBuffer", referenced from:
-[MainViewController imageFromSampleBuffer:] in MainViewController.o
"_CVPixelBufferGetHeight", referenced from:
-[MainViewController imageFromSampleBuffer:] in MainViewController.o
"_kCVPixelBufferPixelFormatTypeKey", referenced from:
_kCVPixelBufferPixelFormatTypeKey$non_lazy_ptr in MainViewController.o
(maybe you meant: _kCVPixelBufferPixelFormatTypeKey$non_lazy_ptr)
"_CVPixelBufferGetWidth", referenced from:
-[MainViewController imageFromSampleBuffer:] in MainViewController.o
"_CVPixelBufferGetBytesPerRow", referenced from:
-[MainViewController imageFromSampleBuffer:] in MainViewController.o
"_CMTimeMake", referenced from:
-[MainViewController setupCaptureSession] in MainViewController.o
"_CVPixelBufferGetDataSize", referenced from:
-[MainViewController imageFromSampleBuffer:] in MainViewController.o
ld: symbol(s) not found
collect2: ld returned 1 exit status
回答1:
Once again, I answer my own question.... I needed to add the CoreVideo and CoreMedia frameworks too.
回答2:
I spent a couple hours struggling with this a variation of this issue. I am posting this to help anybody else who might be in the same situation. I had already linked CoreVideo & CoreMedia to my project. However, I was still experiencing this issue. After a lot of searching around and trying different things I came across this post. Here is my fix:
1) Remove the problematic libraries (CoreVideo and CoreMedia in my case). Do this by deleting them in the project nav and selecting "Remove References" and in the removing them from linked frameworks in "Build Phases"
2) Add the frameworks again, clean, and recompile.
来源：https://stackoverflow.com/questions/3393239/why-wont-avfoundation-link-with-my-xcode-3-2-3-iphone-4-0-1-project