Function retrieve text ID of Mediainfo field by index with given parameters.
GetID(FieldIndex [, Context, Stream])
| FieldIndex | Field index. |
| Context | Context (General, Video, etc.). If omitted, General context will be used. |
| Stream | Stream number. If omitted, stream 0 will be used. Total count of strams can be retrieved with GetCount function. |
Function return string with field's text ID.