[FFmpeg-devel] mpeg12dec fix up DVD caption handling

[Michael Niedermayer]

On Mon, Sep 12, 2016 at 06:19:43PM -0700, Jonathan Campbell wrote:
> 
> 
> On 09/12/2016 04:56 PM, Michael Niedermayer wrote:
> > On Mon, Sep 12, 2016 at 03:28:24PM -0700, Jonathan Campbell wrote:
> >> These patches fix up the DVD caption handling in mpeg12dec.c to better handle odd cases.
> >> It's based on code I've written elsewhere to handle captions.
> >> While it's common for these packets to contain 15 frames worth and start on the odd field there are also DVDs that start on even field or even encode extra fields and switch starting fields.
> >> Part of the patch is to document comprehensively the format of the DVD caption packet.
> >>
> >> Jonathan Campbell
> > 
> >>  mpeg12dec.c |   27 ++++++++++++++++++++++++++-
> >>  1 file changed, 26 insertions(+), 1 deletion(-)
> >> a839a0d0e9000ab140f6aef9dee9577f242462bf  0001-add-comments-documenting-the-format-of-the-DVD-CC-us.patch
> >> From 9213012c7d8ceef2af43fe3c218b1b50728e8f80 Mon Sep 17 00:00:00 2001
> >> From: Jonathan Campbell <jonathan at castus.tv>
> >> Date: Mon, 12 Sep 2016 12:34:48 -0700
> >> Subject: [PATCH 1/2] add comments documenting the format of the DVD CC
> >>  user-data packet. this is to aid development and maintenance of that code.
> >>
> >> ---
> >>  libavcodec/mpeg12dec.c | 27 ++++++++++++++++++++++++++-
> >>  1 file changed, 26 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/libavcodec/mpeg12dec.c b/libavcodec/mpeg12dec.c
> >> index 204a578..522621a 100644
> >> --- a/libavcodec/mpeg12dec.c
> >> +++ b/libavcodec/mpeg12dec.c
> >> @@ -2262,7 +2262,32 @@ static int mpeg_decode_a53_cc(AVCodecContext *avctx,
> >>          return 1;
> >>      } else if (buf_size >= 11 &&
> >>                 p[0] == 'C' && p[1] == 'C' && p[2] == 0x01 && p[3] == 0xf8) {
> >> -        /* extract DVD CC data */
> >> +        /* extract DVD CC data
> > 
> >> +         * for more information see: [https://en.wikipedia.org/wiki/EIA-608#DVD_GOP_User_Data_Insertion]
> > 
> > wikipedia is not a good reference, in fact its not even a
> > constant reference without a revission. wikipedia can massivly change
> > and may at times, especially with niche areas be just wrong, the link
> > itself also wont always work possibly
> > 
> > Please use the specifications itself, H.262 is public, its the 4th
> > link when searching for H.262 with google for example (wikipedia
> > refers to H.262 IIUC)
> > 
> > [...]
> > 
> > 
> > 
> > _______________________________________________
> > ffmpeg-devel mailing list
> > ffmpeg-devel at ffmpeg.org
> > http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> > 
> Updated patch set, removes Wikipedia link.
> 
> I see that H.262 specs are free on the web, but I can't find the part that describes the DVD-style H.262 user data packets that this code handles.
> 
> But the structure as described has been reliable when tested against my DVD library.

applied the docs and wiki removial stashed

please dont send multiple patches per mail it makes keeping track of
what needs a review hard both with MUAs as well as patchwork

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

In a rich man's house there is no place to spit but his face.
-- Diogenes of Sinope
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