Fs1 captioning conversion – AJA FS1 Version 2.2.0.47 User Manual
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FS1 Installation and Operation Manual — 30.1 Closed Captioning Translator
In standard definition video (525i59.94), closed captioning data is encoded and sent
on line 21 of both fields, using a format defined by the Consumer Electronics
Association standard, CEA-608. This is traditionally called “line 21", “SD”, or “608”
captioning, and is used for analog composite, analog component, and serial digital
(SDI) video.
In high definition video, closed captioning is encoded and sent as Vertical Ancillary
(VANC) packets in SDI video, using a format defined by the Consumer Electronics
Association standard CEA-708 (there is no equivalent for analog HD video). This is
traditionally called “HD,” “DTV,” or “708” captioning. The data formatting and
encoding for 708 captions is very different from the data contained in 608 (SD)
captioning, reflecting the added features and capabilities available with the CEA-708
standard.
The FS1 UpConverter automatically translates incoming line 21 captions to CEA-
708 format and inserts the VANC packets into the converted HD video stream. This
is a complete translation from CEA-608 format to CEA-708 format (including the
embedded SD captions).
The FS1 DownConverters automatically intercept and reformat the SD caption data
in the incoming CEA-708 VANC packets, and output it on line 21 of the standard
definition outputs.
To pass closed captioning data to the outputs, parameter 31.1 UC Line 21 must also
be set to Pass. The FS1 CrossConverters will reformat and pass any incoming CEA-
708 VANC packets for the output frame rate.
FS1 Captioning Conversion
SD
Output
525i59.94
Input
SD 525i59.94
1
HD 720p59.94
3
HD1080i59.94
3
HD1080pSF23.98
3
Output
Input
SD 625i50
HD 720p50
HD1080i50
Key
1 - Line 21 (CEA-608) passthrough
2 - Line 21 (CEA-608) to SMPTE-334 (CEA-708) upconversion
3 - SMPTE-334 (CEA-708) to Line 21 (CEA-608) downconversion
4 - SMPTE-334 (CEA-708) passthrough
5 - SMPTE-334 (CEA-708) reframing for change in frame rate
1080pSF23.98
720p59.94
1080i59.94
HD
HD
HD
2
4
5
-
2
5
4
-
n/a
n/a
n/a
4
SD
HD
HD
625i50
720p50
1080i50
-
-
-
-
-
-
-
-
-