这几天我一直在努力寻找在 iPhone 上使用 AudioQueue 服务播放网络音频流(MP3 数据包格式)的方法。
为了成功实现这个目标,我先用AudioQueue把普通的本地MP3文件拿来播放,果然可以。然后,我用 stdio 函数 fread 替换了 AudioFileReadPackets,每次我都像 AudioFileReadPackets 一样 fread 相同数量的 mp3 数据包,以模拟来自网络的音频流。然而,这一次,错误来了:
2011-09-28 14:21:28.245 SunFlower[1554:207] Prime: Exiting because mConverterError is -50 (0x11940 req, 0x0 primed)
2011-09-28 14:21:28.253 SunFlower[1554:207] Prime failed (-50); will stop (72000/0 frames)
有人知道这个“Prime failed (-50)”错误的原因吗?帮忙zzzzzzz
*********************************************** ****************************************************** ****************************************************** *********************。
为了解释我在替换工作上做了什么,我想向您展示代码的主要更改部分,有两部分:“替换前”和“替换后”
- 替换前(播放本地 MP3 文件):
1) 音频队列runloop回调
static void HandleOutputBuffer(void *aqData,
AudioQueueRef inAQ,
AudioQueueBufferRef inBuffer)
{
AQPlayerState *pAqData = (AQPlayerState *) aqData;
UInt32 numBytesReadFromFile;
UInt32 numPackets = pAqData->mNumPacketsToRead;
UInt32 i = 0;
printf("HandleOutputBuffer::Start!\n");
//If the audio queue is stopped, returns immediately
if(pAqData->mIsRunning == 0)
{
printf("HandleOutputBuffer::Error Return!\n");
return;
}
//Read a packet of audio data from file stream
AudioFileReadPackets(pAqData->mAudioFile,
false,
&numBytesReadFromFile,
pAqData->mPacketDescs,
pAqData->mCurrentPacket,
&numPackets,
inBuffer->mAudioData);
//Enqueue the audio packet into the audio queue
if(numPackets > 0)
{
printf("HandleOutputBuffer::Step 1!\n");
inBuffer->mAudioDataByteSize = numBytesReadFromFile;
AudioQueueEnqueueBuffer(pAqData->mQueue,
inBuffer,
(pAqData->mPacketDescs ? numPackets : 0),
pAqData->mPacketDescs);
pAqData->mCurrentPacket += numPackets;
}
else
{
printf("HandleOutputBuffer::Step 2!\n");
AudioQueueStop(pAqData->mQueue,
false);
pAqData->mIsRunning = false;
}
}
2) 打开音频文件
OSStatus AqOpenAudioFile(char *filePath, AQPlayerState *pAqData)
{
CFURLRef audioFileURL;
OSStatus result;
UInt32 maxPacketSize;
UInt32 propertySize = sizeof (maxPacketSize);
audioFileURL =
CFURLCreateFromFileSystemRepresentation(NULL,
(const UInt8 *) filePath,
strlen (filePath),
false);
result = AudioFileOpenURL(audioFileURL,
kAudioFileReadPermission,
0,
&(pAqData->mAudioFile));
CFRelease(audioFileURL);
AudioFileGetProperty(pAqData->mAudioFile,
kAudioFilePropertyPacketSizeUpperBound,
&propertySize,
&maxPacketSize);
DeriveBufferSize(pAqData->mDataFormat,
maxPacketSize,
0.5,
&(pAqData->bufferByteSize),
&(pAqData->mNumPacketsToRead));
return result;
}
3) 创建音频队列
OSStatus AqCreateAudioQueue(AQPlayerState *pAqData)
{
UInt32 dataFormatSize = sizeof (AudioStreamBasicDescription);
OSStatus result;
bool isFormatVBR;
UInt32 cookieSize = sizeof (UInt32);
bool couldNotGetProperty;
AudioFileGetProperty(pAqData->mAudioFile,
kAudioFilePropertyDataFormat,
&dataFormatSize,
&(pAqData->mDataFormat));
result = AudioQueueNewOutput(&(pAqData->mDataFormat),
HandleOutputBuffer,
pAqData,
CFRunLoopGetCurrent(),
kCFRunLoopCommonModes,
0,
&(pAqData->mQueue));
//Configurate the VBR property if any
isFormatVBR = (pAqData->mDataFormat.mBytesPerPacket == 0 ||
pAqData->mDataFormat.mFramesPerPacket == 0);
if(isFormatVBR)
{
pAqData->mPacketDescs =
(AudioStreamPacketDescription*)malloc(pAqData->mNumPacketsToRead * sizeof(AudioStreamPacketDescription));
}
else
{
pAqData->mPacketDescs = NULL;
}
//Set Metadata for Audio Queue
couldNotGetProperty =
AudioFileGetPropertyInfo(pAqData->mAudioFile,
kAudioFilePropertyMagicCookieData,
&cookieSize,
NULL);
if (!couldNotGetProperty && cookieSize)
{
char* magicCookie = (char *)malloc(cookieSize);
AudioFileGetProperty(pAqData->mAudioFile,
kAudioFilePropertyMagicCookieData,
&cookieSize,
magicCookie);
AudioQueueSetProperty(pAqData->mQueue,
kAudioQueueProperty_MagicCookie,
magicCookie,
cookieSize);
free(magicCookie);
}
//Set the playback gain
AudioQueueSetParameter(pAqData->mQueue,
kAudioQueueParam_Volume,
AQ_PLAYBACK_GAIN);
}
2。替换后(通过fread获取playbak mp3 data buffer):
为了代码移植顺利,我复制了关键变量的运行时值,如pAqData->bufferByteSize、pAqData->mNumPacketsToRead、pAqData->mDataFormat…等。并在替换代码中使用复制的值直接初始化这些变量。此行为的目的是放弃涉及 AudioToolbox 框架的接口(interface),如:AudioFileOpenURL、AudioFileGetProperty、AudioFileReadPackets……然后,我们可以使用 stdio 函数 fread 直接获取 mp3 数据包。修改后的代码如下所示:
1)音频队列runloop回调(之前的代码中,AudioFileReadPackets读取了338个包,共129792字节,我直接将这些值复制到替换代码中)
static void HandleOutputBuffer(void *aqData,
AudioQueueRef inAQ,
AudioQueueBufferRef inBuffer)
{
AQPlayerState *pAqData = (AQPlayerState *) aqData;
UInt32 numBytesReadFromFile;
UInt32 numPackets = pAqData->mNumPacketsToRead;
UInt32 i = 0;
printf("HandleOutputBuffer::Start!\n");
//If the audio queue is stopped, returns immediately
if(pAqData->mIsRunning == 0)
{
printf("HandleOutputBuffer::Error Return!\n");
return;
}
//Read a packet of audio data using fread
memset(audio_buffer, 0, 327680);
memset(inBuffer->mAudioData, 0, 327680);
pAqData->mPacketDescs->mStartOffset = 0;
pAqData->mPacketDescs->mVariableFramesInPacket = 0;
pAqData->mPacketDescs->mDataByteSize = 384;
numBytesReadFromFile = fread(audio_buffer, sizeof(uint8_t), 129792, source_file);
numPackets = 338;
memcpy(inBuffer->mAudioData, audio_buffer, 327680);
//Enqueue the audio packet into the audio queue
if(numPackets > 0)
{
printf("HandleOutputBuffer::Step 1!\n");
inBuffer->mAudioDataByteSize = numBytesReadFromFile;
AudioQueueEnqueueBuffer(pAqData->mQueue,
inBuffer,
(pAqData->mPacketDescs ? numPackets : 0),
pAqData->mPacketDescs);
pAqData->mCurrentPacket += numPackets;
}
else
{
printf("HandleOutputBuffer::Step 2!\n");
AudioQueueStop(pAqData->mQueue,
false);
pAqData->mIsRunning = false;
}
}
2) 打开音频文件(用fopen代替AudioFileOpenURL)
OSStatus AqOpenAudioFile(char *filePath, AQPlayerState *pAqData)
{
CFURLRef audioFileURL;
OSStatus result;
UInt32 maxPacketSize;
UInt32 propertySize = sizeof (maxPacketSize);
source_file = fopen(filePath, "r");
memset(audio_buffer, 0, 327680);
fread(audio_buffer, sizeof(uint8_t), 32, source_file);
pAqData->bufferByteSize = 327680;
pAqData->mNumPacketsToRead = 338;
return result;
}
3)创建音频队列(直接初始化pAqData->mDataFormat为本地MP3播放模式赋值)
OSStatus AqCreateAudioQueue(AQPlayerState *pAqData)
{
UInt32 dataFormatSize = sizeof (AudioStreamBasicDescription);
OSStatus result;
bool isFormatVBR;
UInt32 cookieSize = sizeof (UInt32);
bool couldNotGetProperty;
memset(&(pAqData->mDataFormat), 0, sizeof(AudioStreamBasicDescription));
pAqData->mDataFormat.mSampleRate = 48000;
pAqData->mDataFormat.mFormatID = 778924083;//mp3 ID
pAqData->mDataFormat.mFramesPerPacket = 1152;
pAqData->mDataFormat.mChannelsPerFrame = 2;
result = AudioQueueNewOutput(&(pAqData->mDataFormat),
HandleOutputBuffer,
pAqData,
CFRunLoopGetCurrent(),
kCFRunLoopCommonModes,
0,
&(pAqData->mQueue));
//Configurate the VBR property if any
isFormatVBR = (pAqData->mDataFormat.mBytesPerPacket == 0 ||
pAqData->mDataFormat.mFramesPerPacket == 0);
if(isFormatVBR)
{
pAqData->mPacketDescs =
(AudioStreamPacketDescription*)malloc(pAqData->mNumPacketsToRead *
sizeof(AudioStreamPacketDescription));
}
else
{
pAqData->mPacketDescs = NULL;
}
//Set the playback gain
AudioQueueSetParameter(pAqData->mQueue,
kAudioQueueParam_Volume,
AQ_PLAYBACK_GAIN);
}
最佳答案
伙计们:
我找到了根本原因!
问题出在函数HandleOutputBuffer(改的)!
因为函数fread每次都要读取338包mp3数据(不是1包),所以[pAqData->mPacketDescs]不是一个单一的变量,它实际上是一个数组,大小为338个数组项。因此,我们必须初始化所有 338 个数组项。
因此,我们需要更改代码:
static void HandleOutputBuffer(void *aqData,
AudioQueueRef inAQ,
AudioQueueBufferRef inBuffer)
{
...
pAqData->mPacketDescs->mStartOffset = 0;
pAqData->mPacketDescs->mVariableFramesInPacket = 0;
pAqData->mPacketDescs->mDataByteSize = 384;
...
}
进入
static void HandleOutputBuffer(void *aqData,
AudioQueueRef inAQ,
AudioQueueBufferRef inBuffer)
{
...
for (i = 0; i < 338; i++)
{
pAqData->mPacketDescs[i].mStartOffset = PACKET_SIZE * i;
pAqData->mPacketDescs[i].mVariableFramesInPacket = 0;
pAqData->mPacketDescs[i].mDataByteSize = PACKET_SIZE;
}
...
}
终于,问题解决了!
关于iphone - 使用 AudioQueue 服务播放 MP3 数据缓冲区 : Prime failed (-50),我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/7593142/