Question

我需要将数据从GL_TEXTURE_EXTERNAL_OES发送到简单的GL_TEXTURE_2D（将Android播放器中的图像渲染到Unity纹理），当前是通过从具有附加源纹理的缓冲区读取像素来完成的。此过程在我的OnePlus 5手机上可以正常工作，但是在小米Note 4，mi a2等手机上的图像上存在一些故障（例如图像非常绿色），并且由于此过程在每帧和每帧都有效，因此存在性能问题读取的像素要比性能更差（即使我的手机在4k分辨率下的fps也较低）。您知道如何优化此过程或以其他方式执行此过程吗？

感谢和问候！

GLuint FramebufferName;
glGenFramebuffers(1, &FramebufferName);
glBindFramebuffer(GL_FRAMEBUFFER, FramebufferName);

glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_EXTERNAL_OES, g_ExtTexturePointer, 0);

if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
{
    LOGD("%s", "Error: Could not setup frame buffer.");
}

unsigned char* data = new unsigned char[g_SourceWidth * g_SourceHeight * 4];
glReadPixels(0, 0, g_SourceWidth, g_SourceHeight, GL_RGBA, GL_UNSIGNED_BYTE, data);

glBindTexture(GL_TEXTURE_2D, g_TexturePointer);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, g_SourceWidth, g_SourceHeight, 0, GL_RGBA, GL_UNSIGNED_BYTE, data);

glDeleteFramebuffers(1, &FramebufferName);
glBindFramebuffer(GL_FRAMEBUFFER, 0);
glBindTexture(GL_TEXTURE_2D, 0);

delete[] data;

更新。 包含此代码的函数和从Unity端调用它的函数

static void UNITY_INTERFACE_API OnRenderEvent(int eventID) { ... }

extern "C" UnityRenderingEvent UNITY_INTERFACE_EXPORT UNITY_INTERFACE_API UMDGetRenderEventFunc()
{
    return OnRenderEvent;
}

从Unity Update函数中调用的是这样的

[DllImport("RenderingPlugin")]
static extern IntPtr UMDGetRenderEventFunc();

IEnumerator UpdateVideoTexture()
{
    while (true)
    {
        ...
        androidPlugin.UpdateSurfaceTexture();
        GL.IssuePluginEvent(UMDGetRenderEventFunc, 1);
    } 
}

Android插件可以做到这一点（surfaceTexture其纹理包含ExoPlayer在其上呈现视频的外部纹理）

public void exportUpdateSurfaceTexture() {
    synchronized (this) {
        if (this.mIsStopped) {
            return;
        }
        surfaceTexture.updateTexImage();
    }
}

Answer 1

在C ++方面：

当您执行new unsigned char[g_SourceWidth * g_SourceHeight * 4];和delete[] data时，您正在每帧创建和销毁像素数据，这取决于纹理大小，这是昂贵的。一次创建纹理数据，然后重新使用它。

一种方法是让C ++端的static变量保存纹理信息，然后使用一个函数初始化这些变量：:

static void* pixelData = nullptr;
static int _x;
static int _y;
static int _width;
static int _height;

void initPixelData(void* buffer, int x, int y, int width, int height) {
    pixelData = buffer;
    _x = x;
    _y = y;
    _width = width;
    _height = height;
}

然后，应重写捕获函数，以删除new unsigned char[g_SourceWidth * g_SourceHeight * 4];和delete[] data，但要使用静态变量。

static void UNITY_INTERFACE_API OnRenderEvent(int eventID)
{
    if (pixelData == nullptr) {
        //Debug::Log("Pointer is null", Color::Red);
        return;
    }

    GLuint FramebufferName;
    glGenFramebuffers(1, &FramebufferName);
    glBindFramebuffer(GL_FRAMEBUFFER, FramebufferName);

    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_EXTERNAL_OES, g_ExtTexturePointer, 0);

    if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
    {
        LOGD("%s", "Error: Could not setup frame buffer.");
    }

    glReadPixels(_x, _y, _width, _height, GL_RGBA, GL_UNSIGNED_BYTE, pixelData);

    glBindTexture(GL_TEXTURE_2D, g_TexturePointer);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, _width, _height, 0, GL_RGBA, GL_UNSIGNED_BYTE, pixelData);

    glDeleteFramebuffers(1, &FramebufferName);
    glBindFramebuffer(GL_FRAMEBUFFER, 0);
    glBindTexture(GL_TEXTURE_2D, 0);
}

extern "C" UnityRenderingEvent UNITY_INTERFACE_EXPORT UNITY_INTERFACE_API
UMDGetRenderEventFunc()
{
    return OnRenderEvent;
}

在C＃端：

[DllImport("RenderingPlugin", CallingConvention = CallingConvention.Cdecl)]
public static extern void initPixelData(IntPtr buffer, int x, int y, int width, int height);

[DllImport("RenderingPlugin", CallingConvention = CallingConvention.StdCall)]
private static extern IntPtr UMDGetRenderEventFunc();

创建纹理信息，将其固定，然后将指针发送到C ++：

int width = 500;
int height = 500;

//Where Pixel data will be saved
byte[] screenData;
//Where handle that pins the Pixel data will stay
GCHandle pinHandler;

//Used to test the color
public RawImage rawImageColor;
private Texture2D texture;

// Use this for initialization
void Awake()
{
    Resolution res = Screen.currentResolution;
    width = res.width;
    height = res.height;

    //Allocate array to be used
    screenData = new byte[width * height * 4];
    texture = new Texture2D(width, height, TextureFormat.RGBA32, false, false);

    //Pin the Array so that it doesn't move around
    pinHandler = GCHandle.Alloc(screenData, GCHandleType.Pinned);

    //Register the screenshot and pass the array that will receive the pixels
    IntPtr arrayPtr = pinHandler.AddrOfPinnedObject();

    initPixelData(arrayPtr, 0, 0, width, height);

    StartCoroutine(UpdateVideoTexture());
}

然后更新纹理，请参见下面的示例。请注意，有两种方法可以更新纹理，如下面的代码所示。如果您遇到Method1问题，请注释掉使用texture.LoadRawTextureData和texture.Apply的两行，以及 un-comment 使用注释1的Method2代码。 ByteArrayToColor，texture.SetPixels和texture.Apply函数：

IEnumerator UpdateVideoTexture()
{
    while (true)
    {
        //Take screenshot of the screen
        GL.IssuePluginEvent(UMDGetRenderEventFunc(), 1);

        //Update Texture Method1
        texture.LoadRawTextureData(screenData);
        texture.Apply();

        //Update Texture Method2. Use this if the Method1 above crashes
        /*
        ByteArrayToColor();
        texture.SetPixels(colors);
        texture.Apply();
        */

        //Test it by assigning the texture to a raw image
        rawImageColor.texture = texture;

        //Wait for a frame
        yield return null;
    }
}

Color[] colors = null;

void ByteArrayToColor()
{
    if (colors == null)
    {
        colors = new Color[screenData.Length / 4];
    }

    for (int i = 0; i < screenData.Length; i += 4)
    {
        colors[i / 4] = new Color(screenData[i],
            screenData[i + 1],
            screenData[i + 2],
            screenData[i + 3]);
    }
}

完成后或脚本将要销毁时取消固定阵列：

void OnDisable()
{
    //Unpin the array when disabled
    pinHandler.Free();
}

Answer 2

拨打glReadPixels总是很慢； CPU不擅长批量数据传输。

理想情况下，您设法说服Unity接受外部图像句柄，并执行整个过程零拷贝，但是如果我无法使用GPU渲染纹理并使用着色器将外部图像传输到RGB表面。

从GL_TEXTURE_EXTERNAL_OES读取到GL_TEXTURE_2D有性能问题和故障

2 个答案: