Angularjs (versions below 1.1.5) does not provide the if/else functionality . Following are a few options to consider for what you want to achieve:

(Jump to the update below (#5) if you are using version 1.1.5 or greater)

1. Ternary operator:

As suggested by @Kirk in the comments, the cleanest way of doing this would be to use a ternary operator as follows:

<span>{{isLarge ? 'video.large' : 'video.small'}}</span>

2. ng-switch directive:

can be used something like the following.

<div ng-switch on="video">
    <div ng-switch-when="video.large">
        <!-- code to render a large video block-->
    </div>
    <div ng-switch-default>
        <!-- code to render the regular video block -->
    </div>
</div>

3. ng-hide / ng-show directives

Alternatively, you might also use ng-show/ng-hide but using this will actually render both a large video and a small video element and then hide the one that meets the ng-hide condition and shows the one that meets ng-show condition. So on each page you’ll actually be rendering two different elements.

4. Another option to consider is ng-class directive.

This can be used as follows.

<div ng-class="{large-video: video.large}">
    <!-- video block goes here -->
</div>

The above basically will add a large-video css class to the div element if video.large is truthy.

UPDATE: Angular 1.1.5 introduced the ngIf directive

5. ng-if directive:

In the versions above 1.1.5 you can use the ng-if directive. This would remove the element if the expression provided returns false and re-inserts the element in the DOM if the expression returns true. Can be used as follows.

<div ng-if="video == video.large">
    <!-- code to render a large video block-->
</div>
<div ng-if="video != video.large">
    <!-- code to render the regular video block -->
</div>