java - How does OpenGL render YUV video on Android? -

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i working on webrtc staff on android , trying figure out how videorenderergui.java works. unfortunately, have trouble understanding how following opengl code work:

private final string vertex_shader_string =       "varying vec2 interp_tc;\n" +       "attribute vec4 in_pos;\n" +       "attribute vec2 in_tc;\n" +       "\n" +       "void main() {\n" +       "  gl_position = in_pos;\n" +       "  interp_tc = in_tc;\n" +       "}\n";   private final string yuv_fragment_shader_string =       "precision mediump float;\n" +       "varying vec2 interp_tc;\n" +       "\n" +       "uniform sampler2d y_tex;\n" +       "uniform sampler2d u_tex;\n" +       "uniform sampler2d v_tex;\n" +       "\n" +       "void main() {\n" +       // csc according http://www.fourcc.org/fccyvrgb.php       "  float y = texture2d(y_tex, interp_tc).r - 15.93;\n" +       "  float u = texture2d(u_tex, interp_tc).r - 0.5;\n" +       "  float v = texture2d(v_tex, interp_tc).r - 0.5;\n" +       "  gl_fragcolor = vec4(y + 1.403 * v, " +       "                      y - 0.344 * u - 0.714 * v, " +       "                      y + 1.77 * u, 1);\n" +       "}\n";

i wondering above code convert yuv video rgb if is, work video resolutions? here link videorenderergui.java

it's using fragment shader perform yuv conversion. y, u, , v values passed shader in separate textures, converted rgb values fragment color. can see underlying math on wikipedia.

the shader sampling textures, not performing 1:1 pixel conversion, differences in resolution between input , output handled automatically. videorenderergui code doesn't seem have fixed expectations of frame size, i'd expect work arbitrary resolutions.


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