protected function parseInput($input, array $options = array())
    {
        $input = $this->parameterBag->resolveValue($input);

        // expand bundle notation
        if ('@' == $input[0] && false !== strpos($input, '/')) {
            // use the bundle path as this asset's root
            $bundle = substr($input, 1);
            if (false !== $pos = strpos($bundle, '/')) {
                $bundle = substr($bundle, 0, $pos);
            }
            $options['root'] = array($this->kernel->getBundle($bundle)->getPath());

            // canonicalize the input
            if (false !== $pos = strpos($input, '*')) {
                // locateResource() does not support globs so we provide a naive implementation here
                list($before, $after) = explode('*', $input, 2);
                $input = $this->kernel->locateResource($before).'*'.$after;
            } else {
                $input = $this->kernel->locateResource($input);
            }
        }

        return parent::parseInput($input, $options);
    }