viel GRÜNE Farbe, an YUV420p --> RGB in OpenGL 2.0 Shader auf iOS

Ich will ein movie-player für iOS mit ffmpeg und OpenGL ES 2.0
aber ich habe einige Probleme. Ausgang RGB-Bild hat eine Menge von GRÜNER Farbe.
Dies ist der code und Bilder

• 480x320 Breite & height:
• 512x512 Textur-Breite & height

Bekam ich einen YUV420p Zeile Daten von ffmpeg AVFrame.

    for (int i = 0, nDataLen = 0; i < 3; i++) {
        int nShift = (i == 0) ? 0 : 1;
        uint8_t *pYUVData = (uint8_t *)_frame->data[i];
        for (int j = 0; j < (mHeight >> nShift); j++) {
            memcpy(&pData->pOutBuffer[nDataLen], pYUVData, (mWidth >> nShift));
            pYUVData += _frame->linesize[i];
            nDataLen += (mWidth >> nShift);
        }
    }

vorzubereiten und textur für Y, U & V-Kanal.

//: U Texture
    if (sampler1Texture) glDeleteTextures(1, &sampler1Texture);

    glActiveTexture(GL_TEXTURE1);
    glGenTextures(1, &sampler1Texture);
    glBindTexture(GL_TEXTURE_2D, sampler1Texture);

    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    //This is necessary for non-power-of-two textures
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    glEnable(GL_TEXTURE_2D);

    glTexImage2D(GL_TEXTURE_2D, 
                 0, 
                 GL_LUMINANCE, 
                 texW / 2, 
                 texH / 2, 
                 0, 
                 GL_LUMINANCE, 
                 GL_UNSIGNED_BYTE,
                 NULL);

    //: V Texture
    if (sampler2Texture) glDeleteTextures(1, &sampler2Texture);

    glActiveTexture(GL_TEXTURE2);
    glGenTextures(1, &sampler2Texture);
    glBindTexture(GL_TEXTURE_2D, sampler2Texture);

    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    //This is necessary for non-power-of-two textures
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    glEnable(GL_TEXTURE_2D);

    glTexImage2D(GL_TEXTURE_2D, 
                 0, 
                 GL_LUMINANCE, 
                 texW / 2, 
                 texH / 2, 
                 0, 
                 GL_LUMINANCE,
                 GL_UNSIGNED_BYTE,
                 NULL);

    //: Y Texture
    if (sampler0Texture) glDeleteTextures(1, &sampler0Texture);

    glActiveTexture(GL_TEXTURE0);
    glGenTextures(1, &sampler0Texture);
    glBindTexture(GL_TEXTURE_2D, sampler0Texture);

    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    //This is necessary for non-power-of-two textures
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    glEnable(GL_TEXTURE_2D);

    glTexImage2D(GL_TEXTURE_2D, 
                 0, 
                 GL_LUMINANCE, 
                 texW, 
                 texH, 
                 0, 
                 GL_LUMINANCE,
                 GL_UNSIGNED_BYTE, 
                 NULL);

Rendering-Teil ist unten.

int _idxU = mFrameW * mFrameH;
int _idxV = _idxU + (_idxU / 4);

//U data
glActiveTexture(GL_TEXTURE1);
glBindTexture(GL_TEXTURE_2D, sampler1Texture);
glUniform1i(sampler1Uniform, 1);

glTexSubImage2D(
                GL_TEXTURE_2D, 
                0, 
                0, 
                0, 
                mFrameW / 2,            //source width
                mFrameH / 2,            //source height
                GL_LUMINANCE,
                GL_UNSIGNED_BYTE, 
                &_frameData[_idxU]);

//V data
glActiveTexture(GL_TEXTURE2);
glBindTexture(GL_TEXTURE_2D, sampler2Texture);
glUniform1i(sampler2Texture, 2);

glTexSubImage2D(
                GL_TEXTURE_2D, 
                0, 
                0, 
                0, 
                mFrameW / 2,            //source width
                mFrameH / 2,            //source height
                GL_LUMINANCE,
                GL_UNSIGNED_BYTE,
                &_frameData[_idxV]);

//Y data
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, sampler0Texture);
glUniform1i(sampler0Uniform, 0);

glTexSubImage2D(
                GL_TEXTURE_2D, 
                0, 
                0, 
                0, 
                mFrameW,            //source width
                mFrameH,            //source height
                GL_LUMINANCE,
                GL_UNSIGNED_BYTE,
                _frameData);

Vertex-Shader & Fragment Shader ist unten.

attribute vec4 Position;
attribute vec2 TexCoordIn;

varying vec2 TexCoordOut;
varying vec2 TexCoordOut_UV;

uniform mat4 Projection;
uniform mat4 Modelview;

void main()
{
    gl_Position = Projection * Modelview * Position;
    TexCoordOut = TexCoordIn;
}



uniform sampler2D sampler0; //Y Texture Sampler
uniform sampler2D sampler1; //U Texture Sampler
uniform sampler2D sampler2; //V Texture Sampler

varying highp vec2 TexCoordOut;

void main()
{
    highp float y = texture2D(sampler0, TexCoordOut).r;
    highp float u = texture2D(sampler2, TexCoordOut).r - 0.5;
    highp float v = texture2D(sampler1, TexCoordOut).r - 0.5;

    //y = 0.0;
    //u = 0.0;
    //v = 0.0;

    highp float r = y + 1.13983 * v;
    highp float g = y - 0.39465 * u - 0.58060 * v;
    highp float b = y + 2.03211 * u;

    gl_FragColor = vec4(r, g, b, 1.0);
}

Y-Textur (Graustufen) ist korrekt, aber U & V hat viel von der Grünen Farbe.
So Finale RGB-Bild (Y+U+V) hat eine Menge von GRÜNER Farbe.
Was ist das problem?

Bitte helfen.
danke.