Blackmagic Forum

Will this unit pass close caption? If so, how?

TV tech wrote:Will this unit pass close caption? If so, how?

As they say, it depends.

If you're converting standard definition video like NTSC then yes, the miniconverter will pass it. In NTSC video, caption data is actually part of the video signal and lives on the odd field of line 21. The converter isn't doing any special processing for it, just treating it like the rest of the video. This is known as EIA-608 captioning.

If you are talking about a high definition analog feed, then no. For one thing, I am not aware that a standard for captions on analog HD video even exists... but even if it does, there would be a considerable amount of processing needed to convert it to EIA-708 format and embed that into the vertical ancillary area of the HD-SDI output.

Regards,

-- Jeff

Our Mini Converter Analog to SDI will only pass the visible raster, so information outside this will not pass. We do not specify the Analog to SDI for closed captioning. The same would be true for the opposite converter, the Mini Converter SDI to Analog. Typically analog connectors on our hardware do not carry metadata, and this functionality is specific to SDI connectors. If there is a specific device you are interested in for captions, if you look through its tech specs and see a section called "SDI Metadata," closed captions will be listed here if it's supported.

Sarah Jones wrote:Our Mini Converter Analog to SDI will only pass the visible raster, so information outside this will not pass. We do not specify the Analog to SDI for closed captioning. The same would be true for the opposite converter, the Mini Converter SDI to Analog. Typically analog connectors on our hardware do not carry metadata, and this functionality is specific to SDI connectors. If there is a specific device you are interested in for captions, if you look through its tech specs and see a section called "SDI Metadata," closed captions will be listed here if it's supported.

Sarah,

In standard definition video, whether analog composite or SD-SDI, closed captioning is part of the visible raster -- it's the odd field line 21, in an NTSC system. It sounds like you're thinking of EIA708 captioning for HD-SDI, which is in fact metadata that may be inserted in the VANC.

At any rate, I verified by actual test this morning that the Analog to SDI Mini Converter does indeed pass line 21 NTSC closed captioning. I was pretty sure it did, since we have a number of them doing various things in our stations...

Regards,

-- Jeff

Jeff,

Yes, if you have this data in the visible raster, it should pass. I offer the previous information as a broader explanation and for those who might have data outside this raster.