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Captioning 720x512 MPEG-2 Videos

This proprietary format is often used for digital delivery of TV commercial spots, such as for DG and Extreme Reach.  The format is similar to a typical 720x486 standard definition video (Picture A), except that there are an extra 26 rows for VBI data encoded at the top of the frame.  The line 21 for closed captions is positioned below the extra 26 rows of VBI data and just above the active video area (Picture B).

720x486 w/line 21 720x512 w/line 21
A: 720x486 w/ Line 21 CC B: 720x512 w/ Line 21 and extra VBI area

If you need to caption these kinds of files regularly, our software will allow you to do all of the captioning in-house.  Or, CPC's service department can caption your 720x512 MPEG-2 file for a one time fee.

Note that CPC software does not convert other kinds of video files into 720x512 MPEG-2 files.  You need other compression software or hardware to do this.  However, CaptionMaker/MacCaption can add captions to the video before the conversion to 720x512 MPEG-2 step (Method 1), or add captions after the conversion to 720x512 MPEG-2 (Method 2).

Method 1:

This method works best if you are starting with a file that has not yet been compressed to MPEG-2 720x512, e.g. coming from your editing system or using an existing ProRes, IMX, etc. file.

  1. Start with a QuickTime 720x486 file (e.g. ProRes, IMX, uncompressed)

  2. Prepare your captions and add line 21 captions to it using our NLE workflow (CaptionMaker-NLE or MacCaption-NLE or higher) using a setting of Row 1, Column 24.

  3. The result will be a QuickTime 720x486 file with your video & audio and also the line 21 captions at the top of the frame. (It will look like Picture A above.)

  4. Bring this video file into your compression program (e.g. Adobe Media Encoder, Telestream Episode or Flip Factory, Rhozet Carbon Coder, Digital Rapids, Sorenson, etc.) and compress it to 720x512 MPEG-2.  As long as your encoder settings are correct, the line 21 captions will be preserved in correct place in the output file, and the extra 26 lines of black space for VBI data will be added to the top as well.  The result will look like Picture B above.

Method 2 (requires special + version of our software):

This method is slower and gives less quality than Method 1 due to the extra compression. This method is used if you already have a 720x512 MPEG-2 file and don't have access to the original master before it was compressed to MPEG-2.

  1. Start with a 720x512 MPEG-2 file which is otherwise already compliant for delivery, but does not contain captions (such a file can be created by software compressors such as Adobe Media Encoder, Episode, Rhozet, Digital Rapids, Sorenson, etc. or certain hardware boards).

  2. Make a proxy version of this movie using VLC or similar free tools to convert it to QuickTime.  This step is necessary if you want to time stamp/auto sync your captions in MacCaption, because MacCaption cannot play native 720x512 422 MPEG-2 files in the movie window.

  3. Prepare captions in CaptionMaker/MacCaption based on the proxy movie.

  4. In MacCaption, go to File > Export > NLE > CCIR 601 4:2:2P@ML.
    In CaptionMaker, go to File > Export, select NLE group, then (Encode CC) MPEG2 720x512 422P@ML (.mpg).

  5. Choose the new file to save as.  In the next dialog, choose your source file (the original 720x512 MPEG-2 file without captions).

  6. Select the bitrate to compress the modified MPEG-2 data.

  7. CaptionMaker/MacCaption will copy the original MPEG-2 data while inserting the line 21 captions into the new MPEG-2 file.  The result will look like Picture B above.


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