[FFmpeg-devel] [RFC] DVB teletext and PTS
Reimar.Doeffinger at gmx.de
Mon Sep 24 19:08:24 CEST 2012
On Mon, Sep 24, 2012 at 03:02:32PM +0200, Wolfram Gloger wrote:
> Reimar Döffinger <Reimar.Doeffinger at gmx.de> writes:
> > when specifying PTS handling for DVB teletext they made quite a mess it
> > seems (see Annex A of ETSI EN 300 472), which resulted in some stations
> > not using sensible PTS values (for example for ORF the teletext PTS
> > values seem to indicate a time multiple hours after the video time,
> Sorry for entering late -- I've seen this (teletext PTS arbitrarily far
> from audio/video) for ages. German stations often share the same
> teletext stream for several completely different programs, so the
> absolute timestamps are completely meaningless, unless you're watching
> the 'main program' of the bouquet.
I don't think this can be quite that way, they can't be sharing
teletext subtitles across all programs.
> Just for illustration, I have the following in my tree which isn't
> perfect but appears to be not far away from what hardware receivers do
> in practice.
I think it will make subtitle timing worse for programs that actually
send proper time-stamps. For normal teletext I'd consider just
processing them as soon as they arrive just fine, but for teletext
good timestamps are useful.
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