Re: MetaData Update for FLAC and OPUS

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Good afternoon,


On Tue, 2019-08-13 at 14:26 +0200, [email protected] wrote:
> I am using the standard Xiph.org FLAC encoder, but I couldn't find any op=
tion to update the meta-data mid-stream.
> Also the FLAC spec says, that it defines VORBIS_COMMENT as the only way t=
o transmit meta-data information.
> This is the only officially supported tagging mechanism in FLAC. There ma=
y be only one VORBIS_COMMENT block in a stream.

> As such, when you state, that meta data is the domain of the encoder; thi=
s seems to ignore this fact, that there is no FLAC encoder support for mid-=
stream title updates.
> This is pretty much the same as for OGG and OPUS!
> As such, please point me to the encoder option you are referring to - as =
you seem to have implemented mid-stream meta-data updates from a FLAC strea=
m, which doesn't exist in the FLAC specs?!


It's all the in specs. In the Ogg specs. See e.g. the overview page
here:
https://xiph.org/ogg/doc/oggstream.html

For Matroska based see:
https://www.matroska.org/technical/specs/index.html
and
https://www.matroska.org/technical/streaming/index.html



> However, for OGG you (ICEcast) implemented meta-data updates via the admi=
n interface.

If you mean "Ogg" by "OGG" and "Icecast" by "ICEcast": No.
If you mean "Ogg/Vorbis" by "OGG": Long ago someone made a mistake and
actually implemented it. It is broken, it us unhelpful, and it even is a
security problem. And most importantly: it is against the specs. Just
don't use it. It's a bug based on a design flaw by Nullsoft to
workaround a design flaw of MP3.


> So why isn't this supported for OPUS and FLAC - as all three formats do u=
se VORBIS_COMMENT and none of the encoders seems to support mid-stream meta=
-data updates.

Because we WILL NOT re-implement 30 year old bugs on new code.


> I am sorry, but I found the answers provided not really suited to my ques=
tions.
>=20
> So any further help is appreciated.
> However, I will also ask the same question to the FLAC and OPUS mailing l=
ist.

See the link above.


> Thanks,
> Bernd
>=20
> -----Urspr=C3=BCngliche Nachricht-----
> Von: Philipp Schafft <[email protected]>=20
> Gesendet: Dienstag, 13. August 2019 14:09
> An: [email protected]
> Cc: [email protected]
> Betreff: Re: [Icecast-dev] MetaData Update for FLAC and OPUS
>=20
> Good afternoon,
>=20
>=20
>=20
> On Tue, 2019-08-13 at 13:36 +0200, [email protected] wrote:
> > It seems, that with FLAC and OPUS streams (not individual files) the so=
ng title (meta data) updates do not work.
> >=20
> > Also the ICEcast admin web interface isn=E2=80=99t working for FLAC and=
 OPUS; while it is working for MP3, AAC as well as OGG streams.
> >=20
> > =20
> >=20
> > I.e. when sending a continuous FLAC or OPUS stream to an ICEcast server=
, it seems impossible to update the meta data mid-stream (like it works for=
 MP3, AAC or OGG).
> >=20
> > I also couldn=E2=80=99t find any way to tell the original FLAC or OPUS =
encoder to perform the meta data update mid-stream.
>=20
> Then that is a limitation of the encoder. You should contact the vendor o=
f your encoder and ask them about it.
>=20
>=20
>=20
> > Any suggestions?
>=20
> See my reply here:
> http://lists.xiph.org/pipermail/icecast/2019-August/014767.html
>=20
>=20
> > Or are mid-stream meta-data updates simply not supported?
>=20
> They are. And support is complete beside that they do not show up on the =
status page for FLAC based streams. But they are passed to the listener cor=
rectly.
>=20
>=20
> > If they support, I would be glad about any info on how to implement the=
m.
>=20
> You must tell your encoder to update the metadata. It's the encoder's job=
 to send them.
>=20
>=20
> > If they are not supported, are there any plans to implement the admin m=
eta data update interface also for FLAC and OPUS?
>=20
> No. As metadata updates are already supported according to all relevant s=
tandards. Anything else would be outside the standards and would likely be =
more harm than good.


--=20
Philipp Schafft (CEO/Gesch=C3=A4ftsf=C3=BChrer)=20
Telephon: +49.3535 490 17 92

L=C3=B6wenfelsen UG (haftungsbeschr=C3=A4nkt)     Registration number:
Bickinger Stra=C3=9Fe 21                     HRB 12308 CB
04916 Herzberg (Elster)                 VATIN/USt-ID:
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