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Embedded Closed Captions - pass through

Will Closed captions embedded in a video file pass through on HDMI?

10 comments

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    Bright Scripters info[at]brightscripters.com

    More details please

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    Pete Opotowsky

    We're not looking to output visible CC from the player, but rather have it decoded/overlayed downstream by another device.

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    Pete Opotowsky

    flow chart

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    Bright Scripters info[at]brightscripters.com

    Can you provide production workflow details?

    Example:

    Using Adobe Premiere

    Exporting to file format _____

     

    Can you provide a link to sample file with embedded cc?

     

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    Pete Opotowsky

    MPEG transport stream + scc file thu Pixeltools Expert Caption.

    Expert Caption adds captions to existing video file without re-encoding video. Result is M2T with embedded captions.

    Could be MPG but the captioning tool can't demux - so MP4 is NG.

     

    working on a sample file

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    Bright Scripters info[at]brightscripters.com

    HDMI can carry CC only if it is part of the visible content.

    What about letting the BrightSign player handle the CC by overlaying on top of the video content, and make it part of the visible content?

    There is such solution, as shown in this post

    https://brightsign.zendesk.com/hc/en-us/articles/218065197-Do-BrightSign-players-support-closed-captioning-or-subtitles-

     

    Basically you would skip the PIxeltools stage, and let the player read a text file such as the scc file, or similar. There would be no need for a decoder, as captions would be part of the video content.

     

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    Pete Opotowsky

    We want the viewer to decide whether or not to display captions.

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    Pete Opotowsky

    The original question remains and is fairly straightforward: does Brightsign pass through cc over hdmi or not? 

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    Bright Scripters info[at]brightscripters.com

    I must admit that CC is not something that I've dealt with.

    Seems like the decoder box in your diagram, might end up being expensive. (Do you have a model for the decoder you could share?)

    If applicable in your case, I'd explore two other options.

    1. Using one player per display, and turn on/off CC as needed.

    2. Instead of distributing video over HDMI, you could distribute over the network through streaming, which would stream the CC info. Use low cost BS player to decode CC and add to the video image. That would enable locally turning on/off CC. Possibly you could use one player as the stream source, and destination players, as many as screens you have.

    Hopefully that helped.

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    Brandon

    Unlike analog broadcast, HDMI doesn't include somewhere to include the closed caption data in the stream.
    "The HDMI standard was not designed to pass closed caption data (for example, subtitles) to the television for decoding.[42] As such, any closed caption stream must be decoded and included as an image in the video stream(s) prior to transmission over an HDMI cable to appear on the DTV. This limits the caption style (even for digital captions) to only that decoded at the source prior to HDMI transmission. This also prevents closed captions when transmission over HDMI is required for upconversion. For example, a DVD player that sends an upscaled 720p/1080i format via HDMI to an HDTV has no way to pass Closed Captioning data so that the HDTV can decode it, as there is no line 21 VBI in that format."
    https://en.wikipedia.org/wiki/HDMI#Audio/video

    Caption display on a TV would only apply to ATSC or QAM input (ie, RF coax) where the TV's decoder can decode the embedded caption or teletext (waves to folks in Europe) data, if it's there and overlay it.  The TV's ATSC or QAM decoder is then the "source" providing input to the display.

    So, it's up to the source device to "burn in" the captions or not.

    I agree with the advice from Bright Scripters - a player at each display would be able to toggle captions on/off, whether those captions are in a sidecar subtitle file, or embedded in the stream.

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