!! IMPORTANT NOTE: This article pertains to version 3 of our playout application. We have improved things in our version 4, check the following article)
If you don't know what are closed captioning, we can say very briefly that Closed Captioning is subtitling. It is text that is overlaid on top of video for the hearing impaired or when you don't speak the language spoken on screen.
Supported formats and limitations
For HD, OnTheAir Video and OnTheAir Node only support:
- CEA-708 captions
- the captions must be in a CEA-708 closed caption track. MXF and QuickTime are supported.
- the supported formats are 1080i29.97 and 720p29.97 or 720p59.94 (note that 720p is only supported since OnTheAir Video and OnTheAir Node 3.4, previous versions only support 1080i29.97)
For SD, we do support Closed Captions:
- CEA-608 captions
- the captions must be embedded in line 21 of the VBI (Line 21 is the second (field 1) and third (field 2) lines on a 720*486 video - so in this case it is NOT a QuickTime track)
- the clip must have the 720x486 format exactly, it won't work with other frame sizes
- in OnTheAir Video or OnTheAir Node, the playback video format must be set to "NTSC", and the resize mode to "Fill"
Closed captioning will only work if the frame size and fps of the file played are the same as the playback format set in OnTheAir Video or OnTheAir Node. It won't work if you play for example a 720p file in a 1080i output, or it won't work either if you play a SD file in an HD output.
1.3. Supported hardware
All AJA and Deltacast support Closed Captioning output. With Blackmagic-Design, only recent devices (the ones created after the 4K ones) will be compatible, so older models (before the advent of 4K) will not be compatible.
1.4. About the direct link
If you are using OnTheAir Video or OnTheAir Node with OnTheAir CG through a direct link, the CEA-708 Closed Captioning is preserved.
HOW TO create files with CC
We have an article that explains this: https://softron.zendesk.com/hc/en-us/articles/360017759879