[FFmpeg-devel] [Read EXIF metadata 3/5] Read EXIF metadata in JPEG input.

[Michael Niedermayer]

On Mon, Aug 05, 2013 at 05:34:30PM +0200, Thilo Borgmann wrote:
> 3/3 rev 2
> 
> -Thilo

>  Changelog             |    1 +
>  libavcodec/Makefile   |    2 +-
>  libavcodec/mjpegdec.c |   43 +++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 45 insertions(+), 1 deletion(-)
> 5d707f5ffce3774183ad8b3fc5e2ba7cee1da329  0003-Read-EXIF-metadata-in-JPEG-input.patch
> From ecf8ec26f11565e4e71a90799072c7d95447ae90 Mon Sep 17 00:00:00 2001
> From: Thilo Borgmann <thilo.borgmann at googlemail.com>
> Date: Mon, 5 Aug 2013 17:25:04 +0200
> Subject: [PATCH 3/3] Read EXIF metadata in JPEG input.
> 
> ---
>  Changelog             |    1 +
>  libavcodec/Makefile   |    2 +-
>  libavcodec/mjpegdec.c |   43 +++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 45 insertions(+), 1 deletions(-)
> 
> diff --git a/Changelog b/Changelog
> index 48f93c7..8d29154 100644
> --- a/Changelog
> +++ b/Changelog
> @@ -8,6 +8,7 @@ version <next>
>  - ffprobe -show_programs option
>  - compand filter
>  - RTMP seek support
> +- read EXIF metadata from JPEG
>  
>  
>  version 2.0:
> diff --git a/libavcodec/Makefile b/libavcodec/Makefile
> index c23d0c8..d873431 100644
> --- a/libavcodec/Makefile
> +++ b/libavcodec/Makefile
> @@ -263,7 +263,7 @@ OBJS-$(CONFIG_MACE6_DECODER)           += mace.o
>  OBJS-$(CONFIG_MDEC_DECODER)            += mdec.o mpeg12.o mpeg12data.o
>  OBJS-$(CONFIG_MICRODVD_DECODER)        += microdvddec.o ass.o
>  OBJS-$(CONFIG_MIMIC_DECODER)           += mimic.o
> -OBJS-$(CONFIG_MJPEG_DECODER)           += mjpegdec.o mjpeg.o
> +OBJS-$(CONFIG_MJPEG_DECODER)           += mjpegdec.o mjpeg.o exif.o tiff_common.o
>  OBJS-$(CONFIG_MJPEG_ENCODER)           += mjpegenc.o mjpeg.o
>  OBJS-$(CONFIG_MJPEGB_DECODER)          += mjpegbdec.o mjpegdec.o mjpeg.o
>  OBJS-$(CONFIG_MLP_DECODER)             += mlpdec.o mlpdsp.o
> diff --git a/libavcodec/mjpegdec.c b/libavcodec/mjpegdec.c
> index c92738f..5f641bc 100644
> --- a/libavcodec/mjpegdec.c
> +++ b/libavcodec/mjpegdec.c
> @@ -39,6 +39,9 @@
>  #include "mjpeg.h"
>  #include "mjpegdec.h"
>  #include "jpeglsdec.h"
> +#include "tiff.h"
> +#include "exif.h"
> +#include "bytestream.h"
>  
>  
>  static int build_vlc(VLC *vlc, const uint8_t *bits_table,
> @@ -215,6 +218,8 @@ int ff_mjpeg_decode_sof(MJpegDecodeContext *s)
>      int len, nb_components, i, width, height, pix_fmt_id;
>      int h_count[MAX_COMPONENTS];
>      int v_count[MAX_COMPONENTS];
> +    AVDictionary **metadata = avpriv_frame_get_metadatap(s->picture_ptr);
> +    AVDictionary *tmp;
>  
>      s->cur_scan = 0;
>      s->upscale_h = s->upscale_v = 0;
> @@ -459,6 +464,10 @@ int ff_mjpeg_decode_sof(MJpegDecodeContext *s)
>              s->avctx->pix_fmt = AV_PIX_FMT_GRAY16;
>      }
>  
> +    // keep metadata alive by hiding AVDictioniary behind *tmp
> +    tmp       = *metadata;
> +    *metadata = NULL;
> +
>      av_frame_unref(s->picture_ptr);
>      if (ff_get_buffer(s->avctx, s->picture_ptr, AV_GET_BUFFER_FLAG_REF) < 0)
>          return -1;
> @@ -466,6 +475,9 @@ int ff_mjpeg_decode_sof(MJpegDecodeContext *s)
>      s->picture_ptr->key_frame = 1;
>      s->got_picture            = 1;
>  
> +    // restore metadata in current buffer
> +    *avpriv_frame_get_metadatap(s->picture_ptr) = tmp;
> +
>      for (i = 0; i < 3; i++)
>          s->linesize[i] = s->picture_ptr->linesize[i] << s->interlaced;
>  
> @@ -1493,6 +1505,37 @@ static int mjpeg_decode_app(MJpegDecodeContext *s)
>          goto out;
>      }
>  
> +    /* EXIF metadata */
> +    if (s->start_code == APP1 && id == AV_RB32("Exif")) {
> +        GetByteContext gbytes;
> +        int ret, le, ifd_offset, bytes_read;
> +
> +        skip_bits(&s->gb, 16); // skip padding
> +
> +        // init byte wise reading
> +        bytestream2_init(&gbytes, align_get_bits(&s->gb), get_bits_left(&s->gb) >> 3);
> +
> +        // read TIFF header
> +        ret = ff_tdecode_header(&gbytes, &le, &ifd_offset);
> +        if (ret) {
> +            av_log(s->avctx, AV_LOG_ERROR, "mjpeg: invalid TIFF header in EXIF data\n");
> +            return ret;
> +        }
> +
> +        bytestream2_seek(&gbytes, ifd_offset, SEEK_SET);
> +

> +        // read all IFDs and store the metadata
> +        while ((ifd_offset = ff_exif_decode_ifd(s->avctx, &gbytes, le, avpriv_frame_get_metadatap(s->picture_ptr))) > 0) {
> +            bytestream2_seek(&gbytes, ifd_offset, SEEK_SET);
> +        }

i suspect this can end in an infinite loop

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

In fact, the RIAA has been known to suggest that students drop out
of college or go to community college in order to be able to afford
settlements. -- The RIAA
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