Improve quality of YUVY and UYVY rendering

Idea is to upload YUYV/UYVY data as 2 textures and use GL_LINEAR like
in biplanar formats. Having proper interpolation of only one texture
(using e.g. mix function) resulted in vertical and horizontal 1 pixel
stripes depending on scale. The reason was float precision and
unexpected value of fract function. Additionally branching in shader
is expensive so this solution should be more performant.

Task-number: QTBUG-62155
Change-Id: I7ceeb09b4a54eecd16640a626b499d638b52c127
Reviewed-by: Christian Stromme <christian.stromme@qt.io>

3 files changed, 27 insertions, 41 deletions

diff --git a/src/qtmultimediaquicktools/qsgvideonode_yuv.cpp b/src/qtmultimediaquicktools/qsgvideonode_yuv.cpp
index 38b5af943..b04c6b38b 100644
--- a/src/qtmultimediaquicktools/qsgvideonode_yuv.cpp
+++ b/src/qtmultimediaquicktools/qsgvideonode_yuv.cpp
@@ -134,16 +134,16 @@ public:
 protected:
     void initialize() Q_DECL_OVERRIDE {
         m_id_matrix = program()->uniformLocation("qt_Matrix");
-        m_id_yuvtexture = program()->uniformLocation("yuvTexture");
-        m_id_imageWidth = program()->uniformLocation("imageWidth");
+        m_id_yTexture = program()->uniformLocation("yTexture");
+        m_id_uvTexture = program()->uniformLocation("uvTexture");
         m_id_colorMatrix = program()->uniformLocation("colorMatrix");
         m_id_opacity = program()->uniformLocation("opacity");
         QSGMaterialShader::initialize();
     }
 
     int m_id_matrix;
-    int m_id_yuvtexture;
-    int m_id_imageWidth;
+    int m_id_yTexture;
+    int m_id_uvTexture;
     int m_id_colorMatrix;
     int m_id_opacity;
 };
@@ -291,7 +291,7 @@ QSGVideoMaterial_YUV::QSGVideoMaterial_YUV(const QVideoSurfaceFormat &format) :
     case QVideoFrame::Format_UYVY:
     case QVideoFrame::Format_YUYV:
     default:
-        m_planeCount = 1;
+        m_planeCount = 2;
         break;
     }
 
@@ -355,12 +355,19 @@ void QSGVideoMaterial_YUV::bind()
 
              if (m_format.pixelFormat() == QVideoFrame::Format_UYVY
               || m_format.pixelFormat() == QVideoFrame::Format_YUYV) {
-                int fw = m_frame.width() / 2;
+                int fw = m_frame.width();
                 m_planeWidth[0] = fw;
-
-                functions->glActiveTexture(GL_TEXTURE0);
-                bindTexture(m_textureIds[0], fw, m_frame.height(), m_frame.bits(), GL_RGBA);
-
+                 // In YUYV texture the UV plane appears with the 1/2 of image and Y width.
+                m_planeWidth[1] = fw / 2;
+                functions->glActiveTexture(GL_TEXTURE1);
+                // Either r,b (YUYV) or g,a (UYVY) values are used as source of YV.
+                // Additionally Y and V are set per 2 pixels hence only 1/2 of image with is used.
+                // Interpreting this properly in shaders allows to not copy or not make conditionals inside shaders,
+                // only interpretation of data changes.
+                bindTexture(m_textureIds[1], m_planeWidth[1], m_frame.height(), m_frame.bits(), GL_RGBA);
+                functions->glActiveTexture(GL_TEXTURE0); // Finish with 0 as default texture unit
+                // Either red (YUYV) or alpha (UYVY) values are used as source of Y
+                bindTexture(m_textureIds[0], m_planeWidth[0], m_frame.height(), m_frame.bits(), GL_LUMINANCE_ALPHA);
             } else if (m_format.pixelFormat() == QVideoFrame::Format_NV12
                     || m_format.pixelFormat() == QVideoFrame::Format_NV21) {
                 const int y = 0;
@@ -473,13 +480,12 @@ void QSGVideoMaterialShader_UYVY::updateState(const RenderState &state,
     Q_UNUSED(oldMaterial);
 
     QSGVideoMaterial_YUV *mat = static_cast<QSGVideoMaterial_YUV *>(newMaterial);
-
-    program()->setUniformValue(m_id_yuvtexture, 0);
+    program()->setUniformValue(m_id_yTexture, 0);
+    program()->setUniformValue(m_id_uvTexture, 1);
 
     mat->bind();
 
     program()->setUniformValue(m_id_colorMatrix, mat->m_colorMatrix);
-    program()->setUniformValue(m_id_imageWidth, mat->m_frame.width());
 
     if (state.isOpacityDirty()) {
         mat->m_opacity = state.opacity();
diff --git a/src/qtmultimediaquicktools/shaders/uyvyvideo.frag b/src/qtmultimediaquicktools/shaders/uyvyvideo.frag
index 905035703..5c62441c2 100644
--- a/src/qtmultimediaquicktools/shaders/uyvyvideo.frag
+++ b/src/qtmultimediaquicktools/shaders/uyvyvideo.frag
@@ -1,22 +1,12 @@
-uniform sampler2D yuvTexture; // UYVY macropixel texture passed as RGBA format
-uniform mediump float imageWidth; // The UYVY texture appears to the shader with 1/2 the image width since we use the RGBA format to pass UYVY
+uniform sampler2D yTexture; // Y component passed as GL_LUMINANCE_ALPHA, in uyvy Y = a
+uniform sampler2D uvTexture; // UV component passed as RGBA macropixel, in uyvy U = r, V = b
 uniform mediump mat4 colorMatrix;
 uniform lowp float opacity;
-
 varying highp vec2 qt_TexCoord;
 
 void main()
 {
-   // For U0 Y0 V0 Y1 macropixel, lookup Y0 or Y1 based on whether
-   // the original texture x coord is even or odd.
-   mediump float Y;
-   if (fract(floor(qt_TexCoord.x * imageWidth + 0.5) / 2.0) > 0.0)
-       Y = texture2D(yuvTexture, qt_TexCoord).a;       // odd so choose Y1
-   else
-       Y = texture2D(yuvTexture, qt_TexCoord).g;       // even so choose Y0
-   mediump float Cb = texture2D(yuvTexture, qt_TexCoord).r;
-   mediump float Cr = texture2D(yuvTexture, qt_TexCoord).b;
+    mediump vec3 YUV = vec3(texture2D(yTexture, qt_TexCoord).a, texture2D(uvTexture, qt_TexCoord).rb);
 
-   mediump vec4 color = vec4(Y, Cb, Cr, 1.0);
-   gl_FragColor = colorMatrix * color * opacity;
+    gl_FragColor = colorMatrix * vec4(YUV, 1.0) * opacity;
 }
diff --git a/src/qtmultimediaquicktools/shaders/yuyvvideo.frag b/src/qtmultimediaquicktools/shaders/yuyvvideo.frag
index 72732cd66..5ce8b7366 100644
--- a/src/qtmultimediaquicktools/shaders/yuyvvideo.frag
+++ b/src/qtmultimediaquicktools/shaders/yuyvvideo.frag
@@ -1,22 +1,12 @@
-uniform sampler2D yuvTexture; // YUYV macropixel texture passed as RGBA format
-uniform mediump float imageWidth; // The YUYV texture appears to the shader with 1/2 the image width since we use the RGBA format to pass YUYV
+uniform sampler2D yTexture; // Y component passed as GL_LUMINANCE_ALPHA, in yuyv Y = r
+uniform sampler2D uvTexture; // UV component passed as RGBA macropixel, in uyvy U = g, V = a
 uniform mediump mat4 colorMatrix;
 uniform lowp float opacity;
-
 varying highp vec2 qt_TexCoord;
 
 void main()
 {
-   // For Y0 U0 Y1 V0  macropixel, lookup Y0 or Y1 based on whether
-   // the original texture x coord is even or odd.
-   mediump float Y;
-   if (fract(floor(qt_TexCoord.x * imageWidth + 0.5) / 2.0) > 0.0)
-       Y = texture2D(yuvTexture, qt_TexCoord).b;       // odd so choose Y1
-   else
-       Y = texture2D(yuvTexture, qt_TexCoord).r;       // even so choose Y0
-   mediump float Cb = texture2D(yuvTexture, qt_TexCoord).g;
-   mediump float Cr = texture2D(yuvTexture, qt_TexCoord).a;
+    mediump vec3 YUV = vec3(texture2D(yTexture, qt_TexCoord).r, texture2D(uvTexture, qt_TexCoord).ga);
 
-   mediump vec4 color = vec4(Y, Cb, Cr, 1.0);
-   gl_FragColor = colorMatrix * color * opacity;
+    gl_FragColor = colorMatrix * vec4(YUV, 1.0) * opacity;
 }