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How To Create and Edit Open Captions with AVX Effects

Let's take a look at the Avid AVX SubCap Generator effect.

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As international distribution becomes the norm, open captioning is essential. Open captioning is a common industry term the refers to captioning that is always visible to the viewer. With the Avid AVX SubCap Generator effect you can easily input or import text which is then automatically composited into the video material along with any background effects such as drop shadows or background boxes. The text can be entered manually or imported from files in standard captioning formats and becomes a permanent part of the finished video material. The text created by the SubCap Generator is a form of open captioning and edits to the open captions can be re-exported to update changes in an iterative workflow. The subcap effect is typically used for two different types of text information. Text that provides a translation of the spoken dialogue in a program. In this case we're assuming a viewer can hear the audio for the program, but cannot understand the language in which it is spoken. Alternatively we may be working with text that provides a full description of all of the audio content in a program. Here we're assuming a viewer who cannot hear the audio for the program and needs a description not only of the spoken dialog but also for the sound effects, the character of the music and so on.


You might use the SubCap effect to create text that becomes part of the finished program. Alternatively, you might use the SubCap effect to create text the provides a preview during your production process but that is then replaced in the finished program by closed caption text encoded in the video signal.


The SubCap effect has the following main features. Support for the EBU N19 (.stl) and the Avid DS caption file format including the storage of metadata such as contact and program information. Support for Unicode text entry. Parameter control over many aspects of text appearance including fonts, colors, line length and line spacing. Ability to apply parameter changes made on one caption effect clip to all other caption effect clips on the current track or throughout the entire sequence. And the ability to save sets of parameter values for any caption effect clip as a style-sheet file that you can then apply to other caption effect clips in the same or other sequences.


As with other effects, the SubCap plug-in can be found in the Effects Palette under Generator.


In my timeline, I'm going to add a new video track and then I'll add the SubCap effect to that new track. For more complex delivery requirements we might apply different instances of the effect to different video tracks and then simply toggle between them to create various language outputs. In this particular workflow, we're going to import an STL file. This file was created by a subtitling service. The STL files are quite small and can be sent as an email attachment. Before we do that, we will quickly run through the parameters in the plug-in. In doing so, we will setup a default style-sheet. Let's just add some text, adjust the size, opacity, shadow, then we'll center the text, remove the background. Once we have created a style that we like, we go to the global properties page. Many of the tabs reflect aspects of the STL specification such as Program Name, Program Title, Version, Creation Date, etc. The synchronize tab sets the priorities for which properties will propagate, or not, through to other captions when a style-sheet is applied.  By selecting track the style-sheet will apply to all titles on the same track. By selecting program they will apply to all tracks in the program. This allows for flexibility in styles for different tracks if needed. Once complete we will go to the Stylesheet tab and save these parameters as a new style. This window allows for multiple styles to be saved. One can also be setup as a default.


The next parameter is the import-export selection. From here we can select the STL file as sent to us from the subtitle service. Once selected you can see how many captions are in the file, the timecode range of the sequence as well as the timecode range of the file. Since the captions are all based on timecode for placement the import dialog will alert you if the captions fall out of the range. To see in advance whether an import will be successful is another nice feature of this tool. Once the STL file is imported you will see all the captions placed as individual titles on the timeline. These are created by the start and end timecodes in the file for each caption. Lets go to the first title. It does not yet appear with the style we created earlier, so with this title selected, let's go back to the global properties and stylesheets. Highlight the style we saved earlier and apply. All the captions now have the same look and feel. Plus, this is a real-time effect ready for playout. Now if changes need to be made, you can easily go to the edit master caption list. Where you can see all the captions on the current track. You can also edit all the text in a single view. Or, add a return carriage if you want  to break it at a certain spot.


Now lets add some open captions manually. I can add a subcap to each span of dialog in the timeline. And then I can enter the text for the first dialog and apply a pre-made style. Now when I make the second title active and start typing, you will see it automatically inherits the properties of the same style. This is a rapid way to create subtitles directly. And of course, each title can easily be moved and repositioned along with its sync track as needed.


Another great feature of this tool is the ability to create a new STL file that reflects any changes or corrections made to the sub-titles or captions. The DS Caption File can be exported as well. This text file is portable, easy to read and useful for things like legal sign-off or rights management. Also, because the file is easy to edit it can be sent to a translator and a new file can be returned.


Exporting an STL file can also be used in many DVD authoring applications as a subtitle track. Creating even more value for your productions or for your customer.


The AVX SubCap Effect Generator is a new feature available with:

  Avid Media Composer Software v3.0 and above  Upgrade or Buy Online | Request Info

  Avid Symphony v3.0 and above  Request Info

  Avid NewsCutter Software v7.0 and above  Request Info

Also available on Avid Nitris DX and Avid Mojo DX system configurations.


Editor's Note: Thank you to Lesley Glorioso, Michael Phillips and Steve Holyhead for writing this tutorial. Additional thanks to Steve Holyhead for creating and presenting this video.

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