4.18 For each pre-recorded synchronised time-based media that has subtitles, can these be vocalised (excluding special cases)?

Test 1 (4.18.1)

1. Locate pre-recorded synchronised time-based media with subtitles.
2. Check for the presence of an audio track that would be the vocalised version of the subtitles:
   1. activate the sound track;
   2. check that the vocalised subtitles correspond to the displayed subtitles.
3. If not, check that there is a feature that allows you to voice subtitles:
   1. Text-to-speech. Some media players (e.g. <a href="https://ableplayer.github.io/ableplayer/">AblePlayer</a> or <a href="https://videojs.com">VideoJS</a>) offer the option of adding a description track in the form of a text file (similar in construction to a subtitle file with a time stamp) that can be synthesised using the Web Speech API of browsers (this is known as text-to-speech, or TTS). By activating this feature, the browser reads the description. This feature can be used to provide a vocalised version of subtitles and would therefore be considered a compliant implementation if properly documented for the user. To test it:
      1. activate the feature;
      2. start playing the multimedia content;
      3. check that the texts displayed by this means are vocalised.
   2. Description. Some media players (for example, <a href="https://ableplayer.github.io/ableplayer/">AblePlayer</a> or <a href="https://player.support.brightcove.com/playback/using-screen-reader-brightcove-player.html">BrightCove</a>) offer the option of integrating description tracks in the form of a text file (similar in construction to a subtitle file with a time stamp) which is declared in the code using the <code><track></code> tag with the <code>kind="descriptions"</code> attribute and whose final implementation has sufficient properties to enable them to be played back by screen readers (presence of the <code>aria-live</code> property, for example). This feature can be used to provide a version of the subtitles that can be vocalised by screen readers and would therefore be considered a compliant implementation if it is properly documented for the user. To test it:
      1. activate the functionality;
      2. activate the screen reader;
      3. check that the texts displayed by this means are vocalised.
4. If not
   1. activate the subtitles;
   2. activate the screen reader;
   3. check that the spoken subtitles match the displayed subtitles.
5. Otherwise
   1. check for alternative media whose soundtracks contain voice-activated subtitles;
   2. check that the spoken subtitles match the displayed subtitles.
6. If this is the case, the test is validated.