User Manual-Mac

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Chapter 7, Configuring Your MXO2 System
Closed caption capture and playback
If you have an SDI video source that contains digital closed caption data in the
VANC (vertical ancillary data space), Matrox 4VANC lets you capture the closed
caption data as an audio track using MXO2’s SDI input, along with the video.
The Matrox 4VANC audio track that contains the closed caption data can then be
used in a supported video application to play back closed captioning through
MXO2’s SDI or analog output.
Matrox 4VANC preserves the SDI VANC closed caption data during capture by
encoding the data into the audio stream using audio track 16. The resulting file is
an uncompressed 24-bit 48 kHz audio file that contains the closed caption data.
You can also create a Matrox 4VANC closed caption audio file using supported
captioning software, such as CPC MacCaption. You can add a Matrox 4VANC
closed caption audio file to any project timeline in your video application, or
transport and store the audio file on any video/audio device as an audio track.
When using MXO2’s SDI input for capture, you can choose to use audio track 16
to preserve the closed caption data that is in your source video’s VANC. Because
audio track 16 is used for capturing closed captioning, that channel will not be
available for capturing audio.
¦NoteClosed caption data that is present in line 21 of a video’s VBI (vertical
blanking interval) is not transferred to an audio track because it is captured by
MXO2 as part of the video signal.
When using MXO2’s SDI or analog output for playback, you can choose to
retrieve and output the Matrox 4VANC closed caption data from your video
application. The closed caption data is retrieved from audio track 16 and output
using MXO2’s SDI or analog output. When Matrox 4VANC is being used, track
16 is muted during playback, therefore it will not be available for playing back
audio. For playback, MXO2 lets you choose whether to embed the closed caption
data in your HD/SD video’s VANC, or in Line 21 of the VBI portion of SD video.
The following steps describe how to enable Matrox 4VANC closed captioning for
capture and playback on MXO2: