[mythtv] [mythtv-commits] Ticket #2468: Mythtranscode removing audio and subtitles and audio tracks swapping places.

[Geoffrey Hausheer]

On 10/18/06, Daniel Kristjansson wrote:
> Don't forget the ivtv (PVR-250) driver, which uses it's own format
> for embedding EIA-608 captions.
eww..didn't realize that.  I'll need to dig up specs on that I guess.

> > So it is a mess.  Converting to DVD standard would be possible for all
> > of these formats, but requires creating new bitmap images, and quality
> > would be hit-and-miss.  DVB-SUB would be easier to convert to, but is
> > not compatible with MPEG2-PS containers in general.  Converting to any
> > other format would be futile as it would require OCR.
> Actually, the DVB teletext, DVB VBI, ATSC EIA-708, and ivtv formats
> could be embedded in the video stream as user data. The DVB-SUB and
> DVD Subtitles can't really be handled that way (you could emboss one
> set of subtitles in the video permanently, but this would be ugly.)
ATSC can't actually be embedded that way (as it is part of the picture
data and not a seperate stream)  well, not in any way that it would be
usable afterward without some post-processing.  Embossing isn't really
an option either as the whole point of the lossless transcoder is to
not reencode frames.  But yes, all of the text-based streams could be
dealt with in some manner.  I was assuming the need for a compliant
format though, which makes it much more work.

> For instance, enabling transcode to a TS format instead of a PS
> format is a much more important enhancement and would make
> implementing captions and additional language streams much more
> doable. Not only could you bring over the captions, subtitles and
> additional audio streams, they would also be in a standard format;
> this means that it would require no changes in the MythTV video
> playback code and they wouldn't require additional ffmpeg hooks.
Yes...This has been near the top of my list for a while.  It requires
a sizable amount of change to libreplex though.  Once done, it should
be possible to preserve subtitles in whatever format they come down
the stream in (though of course you'll lose them if trying to make a
DVD complaint stream)