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

[greeshma]

Greeshma


On Tue, Mar 24, 2015 at 8:06 PM, Devin Heitmueller <
dheitmueller at kernellabs.com> wrote:

> Hi Greeshma,
>
> It's good to see somebody working on EIA-708 support.  A few questions:
>
> Hello,

I actually started working on this 6-7 days back. This is part of
qualification task for Outreach program for women'15.

- It looks like this patch just creates some basic data structures and
> enums.  Do you have additional patches which demonstrate this
> functionality?  I would be hesitant to see anything committed that
> doesn't actually result in a functional change in the code.  I think
> it would be better to see the development happen on some branch, and
> then the entire patch series can be submitted for upstream inclusion
> once you have something that works.  The alternative tends to result
> in code that needs to be heavily refactored as you make it actually
> work, dead code that isn't actually needed in the final solution, and
> introducing new constraints on existing functionality.
>
> As today is the deadline for application i have submitted all i could do
till now. I am right now working on the proper functionalities.


> - 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.
>

Yes, MPEG2 demux has to be modified/extra features are to be added.As per
my knowledge we now send captions included in picture user data.We need to
change the decoder accordingly.

>
> - We need to think about the GUI implications of supporting both
> EIA-608 and 708.  Do we now show eight menu options for CC1-4 for
> EIA-608 and CC1-4 for EIA-708?  Do we automatically pick EIA-708 over
> EIA-608 (or the reverse) if both are present?  Do we have some global
> configuration option which dictates which decoder gets used?
>

EIA 708 has way lot more features than EIA 608.608 is kind of outdated
format.There  is a way to convert 608 format to 708 but vice-versa is not
possible.The transmission options decide which decoder to be used- eia608
uses line 21 transmission whereas eia708 is embedded in MPEG-2 streams.

>
> - The window anchor support we could potentially do without having to
> support multiple subregions, given the current EIA-608 decoder always
> assumes a 32x16 character window.  The anchor support could be simply
> emulated by properly positioning the cursor within that window.
>
> - 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.
>

Thank you for the guidance.I am trying to contribute to it through Outreach
Program for Women -OPW'15.
Even if its not possible i would definitely continue working on this and
finish the decoder.

>
> On Tue, Mar 24, 2015 at 6:14 AM, greeshma <greeshmabalabadra at gmail.com>
> wrote:
> >
> > From 6260d6377da95f0dcc0e92e6342c4f9c540cc145 Mon Sep 17 00:00:00 2001
> > From: greeshmab <greeshmabalabadra at gmail.com>
> > Date: Tue, 24 Mar 2015 10:27:46 +0530
> > Subject: [PATCH] Added basic features of CIA-708 from wiki page
> >
> > Signed-off-by: greeshma <greeshmabalabadra at gmail.com>
> > ---
> >  modules/codec/cc.c | 250
> > +++++++++++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 250 insertions(+)
> >
> > diff --git a/modules/codec/cc.c b/modules/codec/cc.c
> > index 91e35ee..89754f6 100644
> > --- a/modules/codec/cc.c
> > +++ b/modules/codec/cc.c
> > @@ -1132,3 +1132,253 @@ static char *Eia608Text( eia608_t *h, bool
> b_html )
> >          Eia608Strlcat( psz, "</text>", i_size );
> >      return psz;
> >  }
> > +
> > +
> > +//Based on the Eia708 Wikipedia page
> > +//For SetPenAttributes function, Code is based on CCExtractor code
>
> This could be a problem.  The current code for cc.c is LGPL, and using
> code from CCExtractor will result in the module having to be GPL
> licensed.
>
> Devin
>
>
> --
> Devin J. Heitmueller - Kernel Labs
> http://www.kernellabs.com
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