Question

关于iOS SDK CMBufferQueueCreate的

Reading the documentation，它表示需要getDuration和版本，其他所有回调都可以为NULL。

但运行以下代码：

CFAllocatorRef allocator;
CMBufferCallbacks *callbacks;
callbacks = malloc(sizeof(CMBufferCallbacks));
callbacks->version = 0;
callbacks->getDuration = timeCallback;
callbacks->refcon = NULL;
callbacks->getDecodeTimeStamp = NULL;
callbacks->getPresentationTimeStamp = NULL;
callbacks->isDataReady = NULL;
callbacks->compare = NULL;
callbacks->dataBecameReadyNotification = NULL;

CMItemCount capacity = 4;

OSStatus s = CMBufferQueueCreate(allocator, capacity, callbacks, queue);

NSLog(@"QUEUE: %x", queue);
NSLog(@"STATUS: %i", s);

with timeCallback：

CMTime timeCallback(CMBufferRef buf, void *refcon){
    return CMTimeMake(1, 1);
}

和队列是：

CMBufferQueueRef* queue;

队列创建失败（queue = 0）并返回状态：

kCMBufferQueueError_RequiredParameterMissing = -12761,

callbacks变量已正确初始化，至少调试器是这样说的。

是否有人使用CMBufferQueue？

Answer 1

据推测，参数没有任何问题。至少与你所写的相同，在CMBufferQueue.h中说明了所需的参数。但看起来你传递一个空指针作为CMBufferQueueRef *参数。我已按如下方式更新了您的示例，它似乎创建了消息循环OK。

CMBufferQueueRef queue;
CFAllocatorRef allocator = kCFAllocatorDefault;
CMBufferCallbacks *callbacks;
callbacks = malloc(sizeof(CMBufferCallbacks));
callbacks->version = 0;
callbacks->getDuration = timeCallback;
callbacks->refcon = NULL;
callbacks->getDecodeTimeStamp = NULL;
callbacks->getPresentationTimeStamp = NULL;
callbacks->isDataReady = NULL;
callbacks->compare = NULL;
callbacks->dataBecameReadyNotification = NULL;

CMItemCount capacity = 4;

OSStatus s = CMBufferQueueCreate(allocator, capacity, callbacks, &queue);

NSLog(@"QUEUE: %x", queue);
NSLog(@"STATUS: %i", s);

时间回调仍然相同。

它看起来不像主题启动器，但我希望它能帮助其他人。

CMBufferQueueCreate需要什么参数？

1 个答案: