10 videos mixed simultaneously would take a lot of processing power. No machine that I have access to would be able to handle it.
My guess is that your problem with [pix_mix] has to do with how it handles multiple texture units in OpenGL.
Theoretically, this could be done with OpenGL shaders (OpenGL has a maximum of 32 texture units, so you could assign each video to its own and then mix them) though it depends on what your graphics card supports. I know some cards won't support more than 8 texture units.
Each [pix_texture] object would need to be assigned a specific texture unit number using a [texunit 1( message, replacing 1 with whatever texture unit you are assigning.
Your fragment shader would probably look something like:
uniform sampler2DRect MyTex1;
uniform sampler2DRect MyTex2;
uniform sampler2DRect MyTex3;
uniform sampler2DRect MyTex4;
uniform sampler2DRect MyTex5;
uniform sampler2DRect MyTex6;
uniform sampler2DRect MyTex7;
uniform sampler2DRect MyTex8;
uniform sampler2DRect MyTex9;
uniform sampler2DRect MyTex10;
varying vec2 texcoord1;
void main (void)
vec4 color1 = texture2DRect(MyTex1, texcoord1);
vec4 color2 = texture2DRect(MyTex2, texcoord1);
vec4 color3 = texture2DRect(MyTex3, texcoord1);
vec4 color4 = texture2DRect(MyTex4, texcoord1);
vec4 color5 = texture2DRect(MyTex5, texcoord1);
vec4 color6 = texture2DRect(MyTex6, texcoord1);
vec4 color7 = texture2DRect(MyTex7, texcoord1);
vec4 color8 = texture2DRect(MyTex8, texcoord1);
vec4 color9 = texture2DRect(MyTex9, texcoord1);
vec4 color10 = texture2DRect(MyTex10, texcoord1);
gl_FragColor = (color1 + color2 + color3 + color4 + color5 + color6 + color7 + color8 + color9 + color10) / 10.;
I haven't tested this with more than 2 videos before, but I will give it a shot and post my results.