highp vec4 c = vec4(0,0,0,0);

        highp float e = floor(log2(av));
        highp float m = exp2(fract(log2(av))) - 1.0;

        c[2] = floor(128.0 * m);
        m -= c[2] / 128.0;
        c[1] = floor(32768.0 * m);
        m -= c[1] / 32768.0;
        c[0] = floor(8388608.0 * m);

        highp float ebias = e + 127.0;
        c[3] = floor(ebias / 2.0);
        ebias -= c[3] * 2.0;
        c[2] += floor(ebias) * 128.0;

        c[3] += 128.0 * step(0.0, -v);

        return c / 255.0;
      }

      void main() {
        float value =