ng-repeat on duplicate key (angular)

What you want to do can be done with two different filters: one to grab a list of unique codec types, and one to grab a list of codecs that fit that type.

CodePen example

HTML

<div ng-app="app">
  <div ng-controller="ctrl">
    <div ng-repeat="codec in streams | unique:'codec_type'">
      {{codec.codec_type}}
      <select ng-model="$parent.selected[codec.codec_type]" ng-options="stream as stream.content for stream in streams | codec:codec.codec_type track by stream.id">
      </select>
    </div>
    Selected streams: {{selected}}
  </div>
</div>

Controller

angular.module('app', [])
  .controller('ctrl', function ($scope) {
    $scope.selected = {
      'video': null,
      'audio': null,
      'subtitle': null
    };
    $scope.streams = [
      {
        id: 0,
        codec_type: 'video',
        content: '1920x1040 - H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10'
      },
      { id: 1,
        codec_type: 'audio',
        content: '5.1(side) - cze - undefined'
      },
      { id: 2,
        codec_type: 'audio',
        content: '5.1(side) - eng - undefined'
      },
      { id: 3,
        codec_type: 'subtitle',
        content: 'cze - Czech'
      },
      { id: 4,
        codec_type: 'subtitle',
        content: 'eng - English'
      }];
  })
  .filter('unique', function () {
    return function (items, id) {
      var filtered = [];
      var ids = {};

      angular.forEach(items, function (item) {
        if (typeof(ids[item[id]]) === 'undefined') {
          filtered.push(item);
          ids[item[id]] = true;
        }
      });

      return filtered;
    };
  })
  .filter('codec', function () {
    return function (items, codec) {
      var filtered = [];

      angular.forEach(items, function (item) {
        if (item.codec_type === codec) {
          filtered.push(item);
        }
      });

      return filtered;
    };
});

Use ngOptions directive.

Check out the angularJs Documentation AngularJS Docs

Example:

<select ng-model="stream" ng-options="stream.codec_type for stream in streams>
   <option value=""> Choose Option </option>
</select>

There are multiple other forms to use ng-options, the one I used is simply:

label for value in array

The link I posted will mention and explain each form in depth, so you can choose which one will properly fit your needs.

CONTROLLER:

var types_array = [];
$scope.isUnique = function (type) {
     if (types_array.indexOf(type) === 1){
         return false;
     } else {
         types_array.push(type);
         return true;
     }
}

HTML:

    <md-input-container ng-repeat="stream in streams">
     <div ng-if=isUnique(stream.codec_type)>
      <label>{{stream.codec_type}}</label>
      <md-select ng-model="stream">
        <md-option value="{{stream.id}}">{{stream.content}}</md-option>
      </md-select>
     </div>
    </md-input-container>