ios - AVSampleBufferDisplayLayer 不在设备上呈现
<p><p>我在 iOS 上使用 AVSampleBufferDisplayLayer 时遇到了困难。我想使用这个层显示一个 CVPixelBuffer，但我无法让它在实际的 iOS 设备上工作。在我的示例应用程序中，我尝试使用以下代码来显示一种颜色像素缓冲区:</p>
<pre><code>@implementation ViewController {
AVSampleBufferDisplayLayer *videoLayer;
}
- (void)viewDidLoad {
;
videoLayer = [ init];
videoLayer.frame = CGRectMake(50, 50, 300, 300);
videoLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;
;
}
@implementation ViewController {
AVSampleBufferDisplayLayer *videoLayer;
}
- (void)viewDidLoad {
;
videoLayer = [ init];
videoLayer.frame = CGRectMake(50, 50, 300, 300);
videoLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;
;
}
- (void)viewDidAppear:(BOOL)animated {
;
;
}
- (void)startVideo {
;
;
}
- (void)drawPixelBuffer {
int imageSize = 100;
static const uint8_t pixel[] = {0x00, 0xAA, 0xFF, 0xFF};
NSMutableData *frame = ;
for (int i = 0; i < imageSize * imageSize; i++) {
;
}
CVPixelBufferRef pixelBuffer = NULL;
CVPixelBufferCreateWithBytes(NULL, imageSize, imageSize, kCVPixelFormatType_32BGRA, , imageSize * 4, NULL, NULL, NULL, &pixelBuffer);
CMSampleBufferRef sampleBuffer = ;
if (sampleBuffer) {
;
CFRelease(sampleBuffer);
}
}
- (CMSampleBufferRef)sampleBufferFromPixelBuffer:(CVPixelBufferRef)pixelBuffer {
CMSampleBufferRef sampleBuffer = NULL;
OSStatus err = noErr;
CMVideoFormatDescriptionRef formatDesc = NULL;
err = CMVideoFormatDescriptionCreateForImageBuffer(kCFAllocatorDefault, pixelBuffer, &formatDesc);
if (err != noErr) {
return nil;
}
CMSampleTimingInfo sampleTimingInfo = kCMTimingInfoInvalid;
err = CMSampleBufferCreateReadyWithImageBuffer(kCFAllocatorDefault, pixelBuffer, formatDesc, &sampleTimingInfo, &sampleBuffer);
if (sampleBuffer) {
CFArrayRef attachments = CMSampleBufferGetSampleAttachmentsArray(sampleBuffer, YES);
CFMutableDictionaryRef dict = (CFMutableDictionaryRef)CFArrayGetValueAtIndex(attachments, 0);
CFDictionarySetValue(dict, kCMSampleAttachmentKey_DisplayImmediately, kCFBooleanTrue);
}
if (err != noErr) {
return nil;
}
formatDesc = NULL;
return sampleBuffer;
}
@end
</code></pre>
<p>这在 iOS 模拟器中运行没有任何问题，但在真实设备上无法运行(没有渲染)。视频层的错误属性始终为 nil，状态始终等于 AVQueuedSampleBufferRenderingStatusRendering。</p>
<p>感谢您的帮助。</p></p>
<br><hr><h1><strong>Best Answer-推荐答案</ strong></h1><br>
<p><p>模拟器中的图形实现要健壮得多，而且您通常可以摆脱在设备上无法运行的东西。常见的原因有两种:</p>
<h3>像素缓冲区应该由 IOSurface 支持</h3>
<p>您正在通过 <code>CVPixelBufferCreateWithBytes</code> 直接映射该缓冲区。再次尝试使用 <code>CVPixelBufferCreate</code> 并将 <code>kCVPixelBufferIOSurfacePropertiesKey</code> 属性设置为空字典。</p>
<pre><code>CVPixelBufferCreate(
NULL,
imageSize,
imageSize,
kCVPixelFormatType_32BGRA,
(__bridge CFDictionaryRef)@{
(id)kCVPixelBufferIOSurfacePropertiesKey: @{}
},
&pixelBuffer);
CVPixelBufferLockBaseAddress(pixelBuffer, 0);
void *bytes = CVPixelBufferGetBaseAddress(pixelBuffer);
// Write image data directly to that address
CVPixelBufferUnlockBaseAddress(pixelBuffer, 0);
</code></pre>
<p>实际上，任何生成这些像素的东西都应该尽可能直接写入 <code>CVPixelBufferRef</code>。</p>
<h3>设备不支持某些格式</h3>
<p>这对于 <code>kCVPixelFormatType_32BGRA</code> 来说似乎极不可能，但我已经看到了仅模拟器支持，例如 <code>kCVPixelFormatType_422YpCbCr8</code>。在这些情况下，必须首先将其转换为兼容格式，或者必须实现自定义渲染器(OpenGL、Metal 等)。</p></p>
<p style="font-size: 20px;">关于ios - AVSampleBufferDisplayLayer 不在设备上呈现，我们在Stack Overflow上找到一个类似的问题：
<a href="https://stackoverflow.com/questions/35365008/" rel="noreferrer noopener nofollow" style="color: red;">
https://stackoverflow.com/questions/35365008/
</a>
</p>
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