Re: [FFmpeg-devel] [PATCH 3/8] libavformat/flacdec: Export samples md5 as metadata

["Tomas Härdin" <git@haerdin.se>]

ons 2025-02-12 klockan 22:55 +0100 skrev Michael Niedermayer:
> Hi
> On Wed, Feb 12, 2025 at 11:56:16AM +0100, Tomas Härdin wrote:
> > tor 2025-02-06 klockan 16:07 +0100 skrev Michael Niedermayer:
> > > Hi Tomas
> > > 
> > > On Wed, Feb 05, 2025 at 03:20:09PM +0100, Tomas Härdin wrote:
> [...]
> > > > diff --git a/libavformat/flacdec.c b/libavformat/flacdec.c
> > > > index 3c317acaee..9f65c25864 100644
> > > > --- a/libavformat/flacdec.c
> > > > +++ b/libavformat/flacdec.c
> > > > @@ -33,6 +33,7 @@
> > > >  #include "replaygain.h"
> > > >  
> > > >  #define SEEKPOINT_SIZE 18
> > > > +#define MD5_BYTE_SIZE 16
> > > >  
> > > >  typedef struct FLACDecContext {
> > > >      FFRawDemuxerContext rawctx;
> > > > @@ -109,6 +110,7 @@ static int flac_read_header(AVFormatContext
> > > > *s)
> > > >          if (metadata_type == FLAC_METADATA_TYPE_STREAMINFO) {
> > > >              uint32_t samplerate;
> > > >              uint64_t samples;
> > > > +            char md5hex[MD5_BYTE_SIZE*2+1]; // hex
> > > > representation
> > > > plus null terminator
> > > >  
> > > >              /* STREAMINFO can only occur once */
> > > >              if (found_streaminfo) {
> > > > @@ -133,6 +135,10 @@ static int
> > > > flac_read_header(AVFormatContext
> > > > *s)
> > > >                  if (samples > 0)
> > > >                      st->duration = samples;
> > > >              }
> > > > +
> > > > +            ff_data_to_hex(md5hex, st->codecpar->extradata+18,
> > > > MD5_BYTE_SIZE, 1 /* lowercase */);
> > > > +            md5hex[sizeof(md5hex)-1] = '\0';
> > > > +            av_dict_set(&s->metadata, "samples_md5", md5hex,
> > > > 0);
> > > 
> > > I think "samples_md5" should be documented, so that other
> > > decoders
> > > can use
> > > the same
> > > i also see a verify_md5() in hevc
> > > and crc seems frequently used in decoders
> > 
> > Documented where? doc/metadata.texi doesn't seem like the place for
> > it.
> > doc/demuxers.texi maybe?
> 
> honestly, i didnt think about "where", just that it should be
> documented
> somewhere

A similar question was raised on IRC. I think a new doc entry for it is
warranted. I'll make a new thread about it

/Tomas
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