[Flac] metaflac --no-utf8-convert complains about UTF

[Jan Stary]

On Dec 05 20:16:47, hans at stare.cz wrote:
> This is 1.3.1 on OpenBSD/amd64.
> The --no-utf8-convert option of metaflac(1) does not work for me:
> 
> $ metaflac --no-utf8-convert --set-tag="Artist=Žoužlíček" aladin.flac
> aladin.flac: ERROR: tag value for 'Artist' is not valid UTF-8
> (You probably can't see the Czech letters properly in my mail,
> but that's beside the point.)
> 
> Indeed, it is not valid UTF8 (it's LATIN2), but isn't metaflac
> supposed to just write it as specified, with this option?

On Dec 06 09:54:55, hans at stare.cz wrote:
> The problem seems to be in
> src/metaflac/operations_shorthand_vorbiscomment.c
> in the set_vc_field() function.
> 
> It does check whether utf conversion is required,
> 
>   /* move 'data' into 'converted', converting to UTF-8 if necessary */
>   if(raw) {
> 	converted = data;
>   }
> 					                  }
> but later checks that FLAC__format_vorbiscomment_entry_is_legal()
> whether or not we are utf converting; and this function, defined
> in ./src/libFLAC/format.c, ultimately calls for utf8len_(s) no matter what.
> So my LATIN2 text fails to be legal, because it's not legal UTF
> -- which, indeed, it isn't.

On Dec 06 12:33:35, martin.leese at stanfordalumni.org wrote:
> METADATA_BLOCK_VORBIS_COMMENT is defined at:
> https://xiph.org/flac/format.html#metadata_block_vorbis_comment
> and VorbisComments at:
> http://www.xiph.org/vorbis/doc/v-comment.html
> 
> Note that a VorbisComment is defined as
> being UTF-8, although metaflac  --no-utf8-convert
> doesn't seem to be behaving as advertised.

Reading the above links, the Vorbis Comment is defined to be UTF8.
What is the purpose of --no-utf8-convert in setting tags then?
To specifically ask for invalid files?

Maybe I am misunderstanding the meaning of --no-utf8-convert.
Perhaps the current behaviour is intended, and --no-utf8-convert
just means "don't bother converting, it is already UTF8".
Which my example isn't, and metaflac rightfully complains.

Can anybody please shed some light on this?

> Finally, Jan might have more luck taking his
> problem with metatflac over to the flac-dev list.

On Dec 06 13:55:16, martin.leese at stanfordalumni.org wrote:
> Even better, he could submit a bug report at:
>     http://sourceforge.net/p/flac/bugs/

Yes, I will move this to flac-dev and file a proper bug report
once I am sure it is a bug, and it's the bug I think it is.

BTW, the other Xiph projects track their issues at https://trac.xiph.org/
- is it intentional that FLAC uses the sourceforge bug tracker?
Is there any relation between the two?

	Jan