Question

我正在通过以下方式从id<MTLTexture>创建CVPixelBufferRef对象：

id<MTLTexture> CreateMTLTexrure(CVMetalTextureCacheRef texture_cache,  
                                CVPixelBufferRef pixel_buffer,  
                                MTLPixelFormat metal_pixel_format, size_t plane,  
                                int height, int width) {  
  CVMetalTextureRef texture_ref;  

  CVReturn err = CVMetalTextureCacheCreateTextureFromImage(  
      kCFAllocatorDefault, texture_cache, pixel_buffer, NULL,  
      metal_pixel_format, width, height, plane, &texture_ref);  

  if (err != kCVReturnSuccess) {  
    // throw error  
    return nil;  
  }  

  id<MTLTexture> texture = CVMetalTextureGetTexture(texture_ref);  

  // 
  // Q: is it safe to do CVBufferRelease(texture_ref) here?
  // 
  return texture;  
}

何时应释放CVMetalTextureRef对象？获得MTLTexture后可以安全释放它吗？

Answer 1

是的，它很安全。 根据Apple文档存档中的sample code，它是在分配后立即发布的，就像这样：

<link href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/4.1.3/css/bootstrap.min.css" rel="stylesheet"/>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/4.1.3/js/bootstrap.min.js"></script>

<div class="container">
  <div class="row">
    <div class="col-4" style="background-color: #7fff7f;">
      <div class="star-rating">
        <span style="width: 65%;"></span>
      </div>
    </div>
    <div class="col-8" style="background-color: #ff7f7f;">
      Something something
    </div>
  </div>
</div>

您还可以查看Google Chromium存储库中的WebRTC source code，他们也以相同的方式发布CVMetalTextureRef。

- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection
{
    CVReturn error;

    CVImageBufferRef sourceImageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
    size_t width = CVPixelBufferGetWidth(sourceImageBuffer);
    size_t height = CVPixelBufferGetHeight(sourceImageBuffer);

    CVMetalTextureRef textureRef;
    error = CVMetalTextureCacheCreateTextureFromImage(kCFAllocatorDefault, _videoTextureCache, sourceImageBuffer, NULL, MTLPixelFormatBGRA8Unorm, width, height, 0, &textureRef);

    if (error)
    {
        NSLog(@">> ERROR: Couldnt create texture from image");
        assert(0);
    }

    _videoTexture[_constantDataBufferIndex] = CVMetalTextureGetTexture(textureRef);
    if (!_videoTexture[_constantDataBufferIndex]) {
        NSLog(@">> ERROR: Couldn't get texture from texture ref");
        assert(0);
    }

    CVBufferRelease(textureRef);
}

什么时候应该发布CVMetalTextureRef？

1 个答案: