CVOpenGLESTextureCacheCreateTextureFromImage在iPad2上速度太慢，需要差不多30ms，太瘋狂了

Question

我使用opengl es在iPad上顯示bgr24數據，我是關於opengl es的新功能，所以在顯示視頻部分，我使用了RosyWriter的一個APPLE樣例代碼。它的工作原理，但CVOpenGLESTextureCacheCreateTextureFromImage函數花費超過30毫秒，而在RosyWriter 其成本可以忽略不計。 我所做的是首先將BGR24轉換爲BGRA像素格式，然後使用CVPixelBufferCreateWithBytes函數創建一個CVPixelBufferRef，然後通過CVOpenGLESTextureCacheCreateTextureFromImage獲得一個CVOpenGLESTeureureRef。我的如下碼，

- (void)transformBGRToBGRA:(const UInt8 *)pict width:(int)width height:(int)height 
{ 
rgb.data = (void *)pict; 

vImage_Error error = vImageConvert_RGB888toARGB8888(&rgb,NULL,0,&argb,NO,kvImageNoFlags); 
if (error != kvImageNoError) { 
    NSLog(@"vImageConvert_RGB888toARGB8888 error"); 
} 

const uint8_t permuteMap[4] = {1,2,3,0}; 

error = vImagePermuteChannels_ARGB8888(&argb,&bgra,permuteMap,kvImageNoFlags); 
if (error != kvImageNoError) { 
    NSLog(@"vImagePermuteChannels_ARGB8888 error"); 
} 

free((void *)pict); 
} 

和變換之後，將生成CVPixelBufferRef，碼作爲以下，

[self transformBGRToBGRA:pict width:width height:height]; 

CVPixelBufferRef pixelBuffer; 
CVReturn err = CVPixelBufferCreateWithBytes(NULL, 
          width, 
          height, 
          kCVPixelFormatType_32BGRA, 
          (void*)bgraData, 
          bytesByRow, 
          NULL, 
          0, 
          NULL, 
          &pixelBuffer); 

if(!pixelBuffer || err) 
{ 
    NSLog(@"CVPixelBufferCreateWithBytes failed (error: %d)", err); 
    return; 
} 

CVOpenGLESTextureRef texture = NULL; 
err = CVOpenGLESTextureCacheCreateTextureFromImage(kCFAllocatorDefault, 
                  videoTextureCache, 
                  pixelBuffer, 
                  NULL, 
                  GL_TEXTURE_2D, 
                  GL_RGBA, 
                  width, 
                  height, 
                  GL_BGRA, 
                  GL_UNSIGNED_BYTE, 
                  0, 
                  &texture); 


if (!texture || err) { 
    NSLog(@"CVOpenGLESTextureCacheCreateTextureFromImage failed (error: %d)", err); 
    CVPixelBufferRelease(pixelBuffer); 
    return; 
} 

的其他代碼幾乎相似RosyWriter樣品，包括着色器。所以我想知道爲什麼， 如何解決這個問題。

Answer 1

與我這些天的研究，我發現爲什麼CVOpenGLESTextureCacheCreateTextureFromImage成本多少時間，當數據量大，這裏是3M的分配，複製和移動操作其成本是相當可觀的，尤其是複製操作。然後用像素緩衝池大大提高CVOpenGLESTextureCacheCreateTextureFromImage的性能，從30ms到5ms，與glTexImage2D（）相同。我作爲以下解決方案：

NSMutableDictionary*  attributes; 
attributes = [NSMutableDictionary dictionary]; 


[attributes setObject:[NSNumber numberWithInt:kCVPixelFormatType_32BGRA] forKey:(NSString*)kCVPixelBufferPixelFormatTypeKey]; 
[attributes setObject:[NSNumber numberWithInt:videoWidth] forKey: (NSString*)kCVPixelBufferWidthKey]; 
[attributes setObject:[NSNumber numberWithInt:videoHeight] forKey: (NSString*)kCVPixelBufferHeightKey]; 

CVPixelBufferPoolCreate(kCFAllocatorDefault, NULL, (CFDictionaryRef) attributes, &bufferPool); 

CVPixelBufferPoolCreatePixelBuffer (NULL,bufferPool,&pixelBuffer); 

CVPixelBufferLockBaseAddress(pixelBuffer,0); 

UInt8 * baseAddress = CVPixelBufferGetBaseAddress(pixelBuffer); 

memcpy(baseAddress, bgraData, bytesByRow * videoHeight); 

CVPixelBufferUnlockBaseAddress(pixelBuffer,0); 

與這個新創建pixelBuffer你可以把它快。

將以下配置添加到屬性可以使其性能達到最佳狀態，小於1ms。

NSDictionary *IOSurfaceProperties = [NSDictionary dictionaryWithObjectsAndKeys: 
                     [NSNumber numberWithBool:YES], @"IOSurfaceOpenGLESFBOCompatibility",[NSNumber numberWithBool:YES], @"IOSurfaceOpenGLESTextureCompatibility",nil]; 

[attributes setObject:IOSurfaceProperties forKey:(NSString*)kCVPixelBufferIOSurfacePropertiesKey];