[FFmpeg-devel] [PATCH 2/5] metadata: add new conversion API

[Michael Niedermayer]

On Mon, Oct 04, 2010 at 08:37:23AM +0200, Anton Khirnov wrote:
> On Mon, Oct 04, 2010 at 02:07:04AM +0200, Michael Niedermayer wrote:
> > On Sun, Oct 03, 2010 at 03:52:54PM -0700, Baptiste Coudurier wrote:
> > > On 10/3/10 12:51 PM, Michael Niedermayer wrote:
> > > > On Sun, Oct 03, 2010 at 09:14:23PM +0200, Anton Khirnov wrote:
> > > >> From: Anton Khirnov <wyskas at gmail.com>
> > > >>
> > > >> Track current metadata format in AVMetadata and add av_metadata_clone()
> > > >> function for copying/replacing metadata.
> > > > [...]
> > > >> index 362a056..a9fb39f 100644
> > > >> --- a/libavformat/avformat.h
> > > >> +++ b/libavformat/avformat.h
> > > >> @@ -198,6 +198,22 @@ void av_metadata_conv(struct AVFormatContext *ctx, const AVMetadataConv *d_conv,
> > > >>                                                     const AVMetadataConv *s_conv);
> > > >>  
> > > >>  /**
> > > >> + * Copy metadata from src to dst, converting between their respective formats.
> > > >> + * dst may be equal to src -- for in-place conversion -- or empty (i.e. a
> > > >> + * pointer to NULL), in both cases it is initialized to dst_fmt format.
> > > >> + * Otherwise dst_fmt is ignored. src may be a pointer to NULL, in which case
> > > >> + * dst is initialized, but nothing is copied.
> > > >> + *
> > > >> + * @param pattern Used to copy only some keys. If non-NULL, it is passed
> > > >> + *                directly to av_metadata_get().
> > > >> + * @param flags   Passed directly to av_metadata_get/set. If pattern is NULL,
> > > >> + *                defaults to AV_METADATA_IGNORE_SUFFIX|AV_METADATA_DONT_OVERWRITE.
> > > >> + * @return >= 0 on success otherwise an error code <0
> > > >> + */
> > > >> +int av_metadata_clone(AVMetadata **src, AVMetadata **dst, const AVMetadataConv *dst_fmt,
> > > >> +                      const char *pattern, int flags);
> > > > 
> > > > in all calls src==dst
> > > > 
> > > > where would that not be so?
> > > 
> > > You want to print "intelligible" metadata in dump_format, this is not
> > > done currently, but should.
> > > 
> > > The easiest way is to create a new AVMetadata and translate.
> > 
> > I imagined that the new metadata api would either
> > export 2 AVMetadata sets (one unchanged and one converted to generic tags)
> > OR
> > that there would be a flag that specifies which of the 2 variants should be
> > exported by a demuxer.
> iirc the original reason why the demuxers export metadata in native
> format is so it can be losslessly muxed to the same format --
> av_metadata_conv() with identical conv tables is a noop. if what you're
> proposing is done then it stops making sense to export the native format
> at all, so we might as well export only generic.
> 
> which OTOH might be exactly what we should do. or is anybody aware of
> anyother reason to export native format?

some people simply might dislike not seeing exactly what is stored in  the file
like auth:blah but rather Author:blah
iam not one of them and i dont really see the need myself ...

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Everything should be made as simple as possible, but not simpler.
-- Albert Einstein
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