[FFmpeg-devel] [PATCH] matroskadec: Export the MuxingApp element value as metadata

[Hendrik Leppkes]

On Sun, Dec 1, 2013 at 8:43 PM, wm4 <nfxjfg at googlemail.com> wrote:
> On Sun, 01 Dec 2013 14:44:58 -0300
> James Almer <jamrial at gmail.com> wrote:
>
>> On 01/12/13 2:28 PM, wm4 wrote:
>> > On Sun, 24 Nov 2013 05:31:48 -0300
>> > James Almer <jamrial at gmail.com> wrote:
>> >
>> >> Signed-off-by: James Almer <jamrial at gmail.com>
>> >> ---
>> >>  libavformat/matroskadec.c | 4 +++-
>> >>  1 file changed, 3 insertions(+), 1 deletion(-)
>> >>
>> >> diff --git a/libavformat/matroskadec.c b/libavformat/matroskadec.c
>> >> index eb3b4e6..b3a6477 100644
>> >> --- a/libavformat/matroskadec.c
>> >> +++ b/libavformat/matroskadec.c
>> >> @@ -253,6 +253,7 @@ typedef struct {
>> >>      uint64_t time_scale;
>> >>      double   duration;
>> >>      char    *title;
>> >> +    char    *muxingapp;
>> >>      EbmlBin date_utc;
>> >>      EbmlList tracks;
>> >>      EbmlList attachments;
>> >> @@ -317,7 +318,7 @@ static EbmlSyntax matroska_info[] = {
>> >>      { MATROSKA_ID_DURATION,           EBML_FLOAT, 0, offsetof(MatroskaDemuxContext,duration) },
>> >>      { MATROSKA_ID_TITLE,              EBML_UTF8,  0, offsetof(MatroskaDemuxContext,title) },
>> >>      { MATROSKA_ID_WRITINGAPP,         EBML_NONE },
>> >> -    { MATROSKA_ID_MUXINGAPP,          EBML_NONE },
>> >> +    { MATROSKA_ID_MUXINGAPP,          EBML_UTF8, 0, offsetof(MatroskaDemuxContext,muxingapp) },
>> >>      { MATROSKA_ID_DATEUTC,            EBML_BIN,  0, offsetof(MatroskaDemuxContext,date_utc) },
>> >>      { MATROSKA_ID_SEGMENTUID,         EBML_NONE },
>> >>      { 0 }
>> >> @@ -1587,6 +1588,7 @@ static int matroska_read_header(AVFormatContext *s)
>> >>          matroska->ctx->duration = matroska->duration * matroska->time_scale
>> >>                                    * 1000 / AV_TIME_BASE;
>> >>      av_dict_set(&s->metadata, "title", matroska->title, 0);
>> >> +    av_dict_set(&s->metadata, "encoder", matroska->muxingapp, 0);
>> >>
>> >>      if (matroska->date_utc.size == 8)
>> >>          matroska_metadata_creation_time(&s->metadata, AV_RB64(matroska->date_utc.data));
>> >
>> > Another issue: how is the user supposed to distinguish between real
>> > metadata (i.e. tags), and random-stuff-dumped-into-the-metadata-dict-
>> > because-there's-no-other-place entries?
>>
>> The user can't and never could, as far as i know.
>> Matroska Tags are read last, for that matter. Currently, if there's a "title"
>> or "creation_time" Tag, the relevant existing dict entries (Which were read
>> from Matroska Elements as seen in the code above) are overwritten.
>> This should probably be prevented, to be honest.
>>
>> And i wouldn't call the values of MATROSKA_ID_TITLE, MATROSKA_ID_MUXINGAPP
>> and MATROSKA_ID_DATEUTC random stuff. They are the actual metadata values
>> for the relevant dict entries, which is why they are read as such.
>
> Yes, but they're not tags.

But they are metadata, which is what the structure in the format is
called. Its not called "tags" :)

- Hendrik