webm类型文件
格式转换插件：https://www.fnordware.com/WebM/
或者用shader实现
```
Shader "SYN/BlackScreenClipTex" {
Properties{
_Color("Alpha Color Key", Color) = (0,0,0,1)
_MainTex("Albedo (RGB)", 2D) = "white" {}
_Range("Range",Range(0,1.01)) = 0.1
}
SubShader{
Tags{ "RenderType" = "Opaque" }
LOD 200
CGPROGRAM
#pragma surface surf BlinnPhong Alpha Blending
#pragma target 3.0
sampler2D _MainTex;
struct Input {
float2 uv_MainTex;
};
float _Range;
float4 _Color;
void surf(Input IN, inout SurfaceOutput o)
{
half4 cc = tex2D(_MainTex, IN.uv_MainTex);
float v = (cc.r + cc.g + cc.b) / 3;
v = 1 - v;
half4 color = half4(v, v, v, v);
float4 oo = float4(1, 0, 0, 0.2);
half4 c = color;
oo.rgb = c.rgb;
if (abs(c.r - _Color.r)<_Range && abs(c.g - _Color.g)<_Range && abs(c.b - _Color.b)<_Range)
{
clip(o.Alpha - 1);
}
else
{
o.Emission = cc;
}
}
ENDCG
}
FallBack "Diffuse"
}
```
