Best way to add CEA-608/CEA-708 closed captions to MP4 files

[Subt]

I noticed by chance that the default Windows 10 media player (Films & TV) supports embedded CEA-608/CEA-708 closed captions (AKA EIA-608/EIA-708).
So far I've found several tools that can demux mp4 files but none that can mux video, audio and CEA-608/CEA-708 files. (I also haven't found a subtitle editor that supports CEA-608/CEA-708 output.)

I've got the following questions:

1. Does anybody know whether the Windows 10 media player (Films & TV) supports both CEA-608 and CEA-708 or only CEA-708?
2. Does the Windows 10 media player (Films & TV) support embedded subtitle formats other than CEA-608/CEA-708?
3. What subtitle tool can convert SRT files to CEA-608/CEA-708 files (or other embedded formats supported by the Windows 10 media player)?
4. What muxer can mux video, audio and CEA-608/CEA-708 files (or other embedded formats supported by the Windows 10 media player)?

(I know that I can select external subtitle files, but some of my friends that I'd like to share my videos with have very limited technical skills.)

[usually_quiet]

Support for CEA/EIA-608 closed captions is actually more common in players than support for CEA/EIA-708 closed captions. VLC is pretty good for CEA/EIA-608. PotPlayer has some ability to play them too. I just tried the Films & TV app, which did not detect the EIA-608 CCs in my mpg file. I don't have a suitable mp4 file to try.

I'm not aware of any good easy-to-use free programs or low-cost easy-to-use consumer programs for doing CEA/EIA closed captioning. CEA/EIA-608 closed captions have been on the to-do list for ffmpeg for a while but I don't know if there has been any progress. I've read that the Open Broadcast Encoder Project on GitHub might do you want but this software doesn't seem like something geared towards ordinary users.

CEA/EIA closed captions are stored in the video's GOP user data, so they aren't an ordinary stream

[Subt]

I just tried the Films & TV app, which did not detect the EIA-608 CCs in my mpg file.

I checked my mp4 file and MediaInfo reported that CC1 was encoded as EIA-608 SCTE 128 / DTVCC Transport.

I don't have a suitable mp4 file to try.

You can try this 39 MB CCExtractor sample file, which works fine with the Films & TV app.

CEA/EIA-608 closed captions have been on the to-do list for ffmpeg for a while but I don't know if there has been any progress.

AFAIK, the latest ffmpeg version can only decode CEA/EIA-608 closed captions.

BTW, the Films & TV app didn't show CEA/EIA-608 subtitles for any of the sample files hosted by PixelTools, but VLC showed most of them. It looks like the Films & TV app only supports SCTE 128 / DTVCC Transport.

[usually_quiet]

You can try this 39 MB CCExtractor sample file, which works fine with the Films & TV app.

I downloaded the sample from CCExtractor's website, and the Movies & TV app displayed closed captions, just as you said. The sample is non-standard for an mpg. MediaInfo says it is a transport stream with H.264/AVC video and AAC audio, despite the mpg extension. However, my TS editor, VideoReDo TV Suite, refused to open this file, reporting that the transport stream has no PID.

BTW, the Films & TV app didn't show CEA/EIA-608 subtitles for any of the sample files hosted by PixelTools, but VLC showed most of them. It looks like the Films & TV app only supports SCTE 128 / DTVCC Transport.

I don't think it's that simple. I have a number of HD resolution TV shows which I recorded as transport streams from cable using a digital cable tuner that takes a CableCARD (A smart card for US linear cable TV). My service provider uses H.264/AVC video and AC3 audio for the HD channels which don't originate from local broadcasters. Windows 10's Movies and TV app played the file but displayed no closed captions although MediaInfo reported the following for the first text stream: Format: EIA-608 Muxing mode: SCTE 128 / DTVCC Transport. I re-muxed the TS file as an MP4 as a test, using VideRedo TV sSuite. Closed captions were still present, but Windows 10's Movies and TV app failed to display them once again.