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using objcblock define a callback function.and need return a objc obj(<AVAudioCompressedBuffer@0x170210290: 0/12288 bytes>). but had error.

Traceback (most recent call last):
File "_ctypes/callbacks.c", line 339, in 'converting callback result'
TypeError: cannot be converted to pointer

def conv_block(self,inNumberOfPackets,buffstat):
    # buffstat: 0-have data 1-no data 2-endOfStream   3-error
    print '@1',inNumberOfPackets,buffstat.contents.value
    buffstat.contents.value = 2
    print '@2',inNumberOfPackets,buffstat.contents.value
    print inBuffer      #<AVAudioPCMBuffer@0x174217ae0: 8192/8192 bytes>
    return inBuffer
    # if using return c_void_p(inBuffer)  Error:cannot be converted to pointer

convblock=ObjCBlock(conv_block,restype=c_void_p,argtypes=[c_void_p,c_int32,POINTER(c_long)])

the restype is a pointer. you have a structure. you want to return a pointer to the structure.

pointer(inBuffer)

You may need to cast(pointer(inBuffer), c_void_p)