Hi, I have recently become interested in ripping DVDs after learning that EIA-608 captions can be essentially 1:1 converted to Advanced SubStation Alpha format, maintaining italics, positions, colors and other formatting stuff.
I wanted to keep a record of certain scenes (by taking photos) from some DVDs using my old childhood CRT. To compare to, or if I have the desire to approximate how it looked on the CRT, and always have a reference as I know the CRT won't last forever.
My last DVD player with composite out just died today trying to get these photos. Disc got stuck to boot, but that's a different problem...
So my question is, can I use something like FFmpeg to take an MPEG-2 video with the EIA captions and encode to e.g. h.264 in "line 21" then play the video using a Wii+MPlayer and have the captions fully decoded by the CRT?
The Wii is the only video player I have with composite output that also allows positioning the video.
I've tried searching but everything seems to be about FFmpeg decoding or extracting the captions, but I want the TV to do it, even if it means the top of the video will have some blinking pixels.
+ Reply to Thread
Results 1 to 8 of 8
VideoReDo TVSuite 6 is the only software that I know of with the ability to re-encode video from MPEG-2 to H.264 while retaining the closed captions as closed captions. It has a free trial so you can test what it does with closed captions before buying. ...but I have to ask why you need to convert from MPEG-2 to H.264?Ignore list: hello_hello, tried, TechLord, Snoopy329
The first link seems to be about embedding the data with the stream without changing the picture, so the CRT wouldnít do anything, I think.
It doesnít have to be H.264, my understanding of how the captions work on DVD is that the player has to apply the data to the picture at a specific line so that the CC decoder will work. This distorts the top of the picture, though it canít be seen because of overscan.
If Iím not mistaken, then any video codec would work. Then again maybe some codecs wouldnít be able to handle the random data, I really have no idea.
However, isn't a Wii supposed to be able to play DVDs?
Last edited by usually_quiet; 22nd Sep 2022 at 18:45. Reason: typoIgnore list: hello_hello, tried, TechLord, Snoopy329
The way EIA-608 captions work is by applying digital Biphase pulses (On/Off, Black/White) to the signal on line 21 (and possibly also 22) for NTSC CC use, based on the "coding" of the caption.
They way those captions get decoded is WITHIN THE CRT/TV, or occasionally an outboard decoder, which after decoding to a separate picture buffer, then overlays them onto the (main) picture at the designated sections of the screen (designated by the encoded data).
Captions work on a DVD player by PASSING the digital MPEG 2 signal (which includes the line21 metadata stored in an auxiliary stream) on to a DAC, which also allows the insertion of the metadata back onto the Line21/22 for ANALOG output.
Note: you cannot put Line21/22 data on most digital images, because Line21/22 do not exist in the digital equivalent.
NTSC uses 525 lines, the digital 601 equivalent of that captures either 486 (pro cards) or 480 (standard pro-sumer cards) lines. For 480, that means that 525-480= 45 lines are not captured, those are usually the 22 1/2 lines above the top of the visible image, and 22 1/2 lines below. So line 21 and 22 don't normally get captured, or if they do, they do not get put into the same place in the file as the normal pixels that DO get captured.
Thus, the need to put them into the MPEG2 auxiliary stream (not main video, not main audio, not subs). Some cards may decode into pixels, some cards may decode into "text", or some other kind of block/character-based data.
Captions ONLY work on analog outputs (RF, Composite, S-Video, Component). They don't work on digital outputs (HDMI, DVI, etc) because those formats don't have provision for them, and because 608 is an ANALOG format. 708 is a digital equivalent, but it was not included in HDMI or DVI (though I believe it is included in broadcast digital transport streams).
The picture is not "distorted" as much as overlay re-written for those lines. But it's not random data but digital code, just not digital data in the same way that the pixels are digital.
Hopefully that makes clear that it is much more difficult to decode+re-encode than if it were simple picture data.
(I see usually_quiet beat me to it)
Thank you all, I have a better understanding now.
Early Wii consoles can play DVD Video with MPlayer ports but CC can only be decoded by the app, and it throws out all the formatting.
Itís pretty barebones, picture subs are grayscale, most DVD menus are glitchy, etc.
Curiously the video encoder has some unofficial documentation that mentions CC controls but itís unknown how it works.
(register address 0x7A)
The only video connections on a TV that are capable of providing analog closed captions on Line 21/22 for a CRT TV to decode and display are composite, S-video, and RF, assuming the TV was made for sale in the USA.
Although the availability of closed captions will be restricted to DVDs, I think that you need a new DVD player with closed caption support and composite out if you want the TV to decode and display closed captions. I can't think of anything else that can provide analog closed captions for a TV to decode and display.
Computers don't have the required analog connections. Blu-ray players made after 2012 only have HDMI connections for video, and those made before 2013 often lacked support for closed captions. Stand-alone media players either decode and overlay closed captions on the picture before sending it to a TV or ignore closed captions.
Last edited by usually_quiet; 22nd Sep 2022 at 21:56.Ignore list: hello_hello, tried, TechLord, Snoopy329