CMBlockBufferCreate内存管理 [英] CMBlockBufferCreate memory management

问题描述

我有一些代码可以创建CMBlockBuffers，然后创建一个CMSampleBuffer并将其传递给AVAssetWriterInput。

I have some code that creates CMBlockBuffers and then creates a CMSampleBuffer and passes it to an AVAssetWriterInput.

这里的内存管理有什么优惠？根据Apple文档，任何内容你使用名称中的'Create'应该与CFRelease一起发布。

What's the deal on memory management here? According to the Apple documentation, anything you use with 'Create' in the name should be released with CFRelease.

但是，如果我使用CFRelease，那么我的应用程序将以'malloc： * 错误：未分配对象被释放。

However, if I use CFRelease then my app aborts with 'malloc: * error for object 0xblahblah: pointer being freed was not allocated.

CMBlockBufferRef tmp_bbuf = NULL;
CMBlockBufferRef bbuf = NULL;
CMSampleBufferRef sbuf = NULL;
status = CMBlockBufferCreateWithMemoryBlock(
                                            kCFAllocatorDefault, 
                                            samples, 
                                            buflen, 
                                            kCFAllocatorDefault, 
                                            NULL, 
                                            0, 
                                            buflen, 
                                            0, 
                                            &tmp_bbuf);

if (status != noErr || !tmp_bbuf) {
    NSLog(@"CMBlockBufferCreateWithMemoryBlock error");
    return -1;
}
// Copy the buffer so that we get a copy of the samples in memory.
// CMBlockBufferCreateWithMemoryBlock does not actually copy the data!
// 
status = CMBlockBufferCreateContiguous(kCFAllocatorDefault, tmp_bbuf, kCFAllocatorDefault, NULL, 0, buflen, kCMBlockBufferAlwaysCopyDataFlag, &bbuf);
//CFRelease(tmp_bbuf); // causes abort?!
if (status != noErr) {
    NSLog(@"CMBlockBufferCreateContiguous error");
    //CFRelease(bbuf);
    return -1;
}


CMTime timestamp = CMTimeMake(sample_position_, 44100);

status = CMAudioSampleBufferCreateWithPacketDescriptions(
    kCFAllocatorDefault, bbuf, TRUE, 0, NULL, audio_fmt_desc_, 1, timestamp, NULL, &sbuf);

sample_position_ += n;
if (status != noErr) {
    NSLog(@"CMSampleBufferCreate error");
    return -1;
}
BOOL r = [audioWriterInput appendSampleBuffer:sbuf]; // AVAssetWriterInput
//memset(&audio_buf_[0], 0, buflen);
if (!r) {
    NSLog(@"appendSampleBuffer error");
}
//CFRelease(bbuf);
//CFRelease(sbuf);

所以，在这段代码中，我应该使用 CFRelease 关于什么？

So, in this code, should I be using CFRelease on anything?

推荐答案

关键是CMBlockBufferCreateWithMemoryBlock的blockAllocator参数：

The key is the blockAllocator parameter to CMBlockBufferCreateWithMemoryBlock:

用于分配memoryBlock的分配器，如果memoryBlock是
NULL。如果memoryBlock为非NULL，则此分配器将用于
解除分配（如果提供）。传递NULL将导致使用默认的
分配器（在调用时设置）。 如果不需要重新分配，则传递
kCFAllocatorNull。

因为你不想要示例当你释放CMBlockBuffer时要解除分配，你想传入kCFAllocatorNull作为第四个参数，如下所示：

Since you don't want the "samples" to be deallocated when you release the CMBlockBuffer, you want to pass in kCFAllocatorNull as the 4th parameter like so:

status = CMBlockBufferCreateWithMemoryBlock(
                                            kCFAllocatorDefault, 
                                            samples, 
                                            buflen, 
                                            kCFAllocatorNull, 
                                            NULL, 
                                            0, 
                                            buflen, 
                                            0, 
                                            &tmp_bbuf);

这篇关于CMBlockBufferCreate内存管理的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！