[vlc-devel] [PATCH] cc.c : Added basic features of CIA-708 to cc.c

[Francois Cartegnie]

Le 24/03/2015 15:36, Devin Heitmueller a écrit :
> - I believe we're currently only feeding the EIA-608 bytes to the cc
> decoder currently.  If we wanted to support EIA-708, the MPEG2 demux
> would need to be modified to create additional decoder instances and
> feed those bytes instead.

Since that's embedded in the MPEG2 stream, that's instanciated by the ES
when mpegvideo decoders/packetizers are providing p_dec->pf_get_cc.
That one returning extracted/collected data from the mpeg2 user data.
Demuxer itself has no knowledge of CC (as opposed to the mp4 demux).

The CC decoder, instanciated from an arbitrary, by channel, fourcc, then
also gather and decodes.

For 708 support, we need to be able to pass more parameters, either
through get_cc or additional call.

We also need to collect DTV cc stream at packetizer & mpeg decoder level.
Currently, cc_types > 2 are skipped. DTV being 3.

> EIA-608 (or the reverse) if both are present?  Do we have some global
> configuration option which dictates which decoder gets used?

none

> - Adding support for some of these features could exacerbate known
> performance issues in the existing SPU renderer.  There are some
> assumptions made with regards to things such as font size and
> positioning which could cause a significant reduction in compositing
> performance if we provide more flexibility as allowed by EIA-708.  I
> can get into more specifics on this in a separate email.

We're already doing this for MP4/tx3g, except positioning.

Francois