[FFmpeg-devel] [Read EXIF metadata 2/3] Add EXIF metadata parser to libavcodec.

[Michael Niedermayer]

On Mon, Aug 12, 2013 at 05:26:08PM +0200, Thilo Borgmann wrote:
> 2/3 rev 8
> 
> -Thilo

>  exif.c |  129 +++++++++++++++++++++++++++++++++++++++++++++++++
>  exif.h |  169 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 298 insertions(+)
> c1043583606bf4275ab73da2db24215d530de13e  0002-Add-EXIF-metadata-parser-to-libavcodec.patch
> From 2e8f9c027f126815976a9605a3d007ed19ae26fa Mon Sep 17 00:00:00 2001
> From: Thilo Borgmann <thilo.borgmann at googlemail.com>
> Date: Mon, 12 Aug 2013 17:16:43 +0200
> Subject: [PATCH 2/3] Add EXIF metadata parser to libavcodec.
> 
> ---
>  libavcodec/exif.c | 129 +++++++++++++++++++++++++++++++++++++++++
>  libavcodec/exif.h | 169 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 298 insertions(+)
>  create mode 100644 libavcodec/exif.c
>  create mode 100644 libavcodec/exif.h
> 
> diff --git a/libavcodec/exif.c b/libavcodec/exif.c
> new file mode 100644
> index 0000000..27f4260
> --- /dev/null
> +++ b/libavcodec/exif.c
> @@ -0,0 +1,129 @@
> +/*
> + * EXIF metadata parser
> + * Copyright (c) 2013 Thilo Borgmann <thilo.borgmann _at_ googlemail.com>
> + *
> + * This file is part of FFmpeg.
> + *
> + * FFmpeg is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2.1 of the License, or (at your option) any later version.
> + *
> + * FFmpeg is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with FFmpeg; if not, write to the Free Software
> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
> + */
> +
> +/**
> + * @file
> + * EXIF metadata parser
> + * @author Thilo Borgmann <thilo.borgmann _at_ googlemail.com>
> + */
> +
> +#include "exif.h"
> +
> +
> +static const char *exif_get_tag_name(uint16_t id)
> +{
> +    int i;
> +
> +    for (i = 0; i < FF_ARRAY_ELEMS(tag_list); i++) {
> +        if (tag_list[i].id == id)
> +            return tag_list[i].name;
> +    }
> +
> +    return NULL;
> +}
> +
> +
> +static int exif_add_metadata(AVCodecContext *avctx, int count, int type,
> +                             const char *name, const char *sep,
> +                             GetByteContext *gb, int le,
> +                             AVDictionary **metadata)
> +{
> +    switch(type) {
> +    case TIFF_DOUBLE   : return ff_tadd_doubles_metadata(count, name, sep, gb, le, metadata);
> +    case TIFF_SHORT    : return ff_tadd_shorts_metadata(count, name, sep, gb, le, metadata);
> +    case TIFF_BYTE     :
> +    case TIFF_UNDEFINED:
> +    case TIFF_STRING   : return ff_tadd_string_metadata(count, name, gb, le, metadata);
> +    case TIFF_SRATIONAL:
> +    case TIFF_RATIONAL : return ff_tadd_rational_metadata(count, name, sep, gb, le, metadata);
> +    case TIFF_SLONG    :
> +    case TIFF_LONG     : return ff_tadd_long_metadata(count, name, sep, gb, le, metadata);
> +    default:
> +        avpriv_request_sample(avctx, "TIFF tag type (%u)", type);
> +        return 0;
> +    };
> +}
> +
> +

> +static int exif_decode_tag(AVCodecContext *avctx, GetByteContext *gbytes, int le,
> +                           unsigned *child_ifds, AVDictionary **metadata)
> +{
> +    int ret, cur_pos;
> +    unsigned id, count;
> +    enum TiffTypes type;
> +
> +    ff_tread_tag(gbytes, le, &id, &type, &count, &cur_pos);
> +
> +    // read count values and add it metadata
> +    // store metadata or proceed with next IFD
> +    ret = ff_tis_ifd(id);
> +    if (ret) {
> +        if (!child_ifds[ret - 1]) {
> +            child_ifds[ret - 1] = 1;
> +            ret = ff_exif_decode_ifd(avctx, gbytes, le, child_ifds, metadata);
> +        }

i think its simpler to check the recursion depth and would then also
be able to handle duplicate tags

also you probably want to add yourself to MAINTAINERS for exif

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

What does censorship reveal? It reveals fear. -- Julian Assange
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