1. MixerHost
* AudioBufferList
Declaration: struct AudioBufferList {
UInt32 mNumberBuffers;
AudioBuffer mBuffers[1];
};
Q:WHY AudioBuffer[1]? WHY NOT AudioBuffer *? seems the same ?
注：參見此文對指針與數據區別的分析：http://wenku.baidu.com/view/93fc57202f60ddccda38a0b5.html
mBuffers只是標明一個buffer array的起始地址，具體空間大小由mNumberBuffers決定。
另外，在本程序裏，mNumberBuffers爲1/2，分別表示mono/stereo，而每個buffer本身只有一個channel
* AudioBuffer
struct AudioBuffer {
UInt32 mNumberChannels;
UInt32 mDataByteSize;
void *mData;
};
typedef struct AudioBuffer AudioBuffer;
Q: 跟蹤發現，mNumberChannels總是1，什麼原因？是否因爲right channel的data在另一個buffer中？和interleaved及non-interleaved之間有什麼關係？
A: 此struct用於多種場景，某些情況下在一個buffer中會有多個channel的數據，有些情況下只有一個channel的數據。與AudioBufferList配合使用。
* InputRenderCallback()
// Audio unit input render callbacks are invoked on a realtime priority thread (the highest
// priority on the system). To work well, to not make the system unresponsive, and to avoid
// audio artifacts, a render callback must not:
//
// * allocate memory
// * access the file system or a network connection
// * take locks
// * waste time
//
// In addition, it's usually best to avoid sending Objective-C messages in a render callback.
//
2. My own Audio Unit code in conference project
* inside InputRenderCallback()
// get audio data from audio engine
readAudioData(buffer, length) // length should be 1280=320*4 bytes
// fill the buffer handed to me
// Fill the buffer or buffers pointed at by *ioData with the requested number of samples
// of audio from the sound stored in memory.
for (UInt32 frameNumber = 0; frameNumber < inNumberFrames; ++frameNumber) {
outSamplesChannelLeft[frameNumber] = dataInLeft[sampleNumber];
}
3. 調試Conference程序使用G711
* playback
errors as follows:
(gdb) continue
2012-03-12 18:03:26.217 test555[1369:207] AQBufferCallback...
2012-03-12 18:03:27.395 test555[1369:207] audio data ready
2012-03-12 18:03:27.395 test555[1369:207] AQBufferCallback...
[Switching to process 1369]
Program received signal: “EXC_BAD_ACCESS”.
other erros:
2012-03-12 18:16:03.056 test555[1475:207] AQBufferCallback...
mi_cmd_exec_interrupt: Inferior not executing.
mi_cmd_exec_interrupt: Inferior not executing.
(gdb) continue
(gdb) continue
2012-03-12 18:16:03.976 test555[1475:207] audio data ready
test555(1475,0xb024f000) malloc: *** error for object 0x551bde4: incorrect checksum for freed object - object was probably modified after being freed.
*** set a breakpoint in malloc_error_break to debug
Program received signal: “SIGABRT”.
(gdb) continue
Program received signal: “SIGABRT”.