The main standard for CC708 is CEA-708, however this document I found to be big, fluffy and I found a couple of contradictions in what it defined (I think it was written too from a software perspective), it also does not define the packets etc needed anyway.

But fortunately the standard has been further defined, ATSC A/65C limits it from the 63 (from memory!) or so channels CC-708 defines to a maximum of 16, the other hardware standards then use this.

The packets of which are defined in SMPTE S334-2-2007, the vertical ancillary mapping is in SMPTE 334-1, all good information if you need to design hardware for SDI at least.

Although finding test equipment to generate 708 captions seems to be a hard task, so far everything comprehensive I have found has been a $10,000+ closed caption encoder to support the full standard, or a $100 device for 608 encoding – the search continues!

For H264, I believe the best way is to use QuickTime since QT has a full blown captioning functions. I see that many players now, including windows media, can play an H.264 movie as long as they have the codec for it, but the caption functionality will be limited to just in the bottom section (or it may not even appear at all).

Let me know some more info, so I can give you a more detailed answer.

A lot of info I wasn’t aware of. My broadcast/webcast operation is switching over to streaming in H.264. How would CC be embedded in these streams? What options would end-users have as far as browser and/or player support for CC delivered this way?

Its a great article. I am wondering if we can embed 608 captions in to h.264 elementary streams… can you through me some light on that…

Thanks,
neuron.

You’ve got that right! It’s really complicated!
Thank You for the phone number. I would love to talk to your engineer Matt…

Tom F

Hello Joanna,

But what about before the content is compressed? When HD is raw or uncompressed at HD-SDI the data has lines and a Vertical & Horizontal Ancillary data region. EIA-708 closed captioning is put on lines 9 through 15. So component video does have a VBI before it’s compressed to an MPEG stream…

Tom Cable

This is an excellent article on a very complex subject. So, my understanding is that EIA-608 closed captioning is the way it’s been done for years on NTSC analog. The data is on line 21 & routes through the RF or composite video output of the converter. You can also go RF right into an analog TV. All the decoding is done internally by the television. SD & HD digital TV is an overlay that is on the HDMI or component video output of the cable converter. Is it correct to say that there’s EIA-608 analog that can only be black on white & that there’s also EIA-608 In EIA-708 (608 in 708) When 608 in 708 is being outputted on a digital set top box, can the ‘digital 608′ be set to display different color characters? or are you still limited to black on white like when you go VBI line 21 into an analog tube TV? Thanks! Tom Cable

Thank you very much for the article. It is very informative.

Thanks,
Hari