Tag writing inefficient?

[eliasp]

Hi,

I've noticed some trouble when re-tagging some of my FLAC albums using Amarok.
Updating the tags of a single FLAC album takes up to 10 minutes, because my
music collection is stored on a NFS share on my fileserver where I connect to
via WLAN.

When writing now the tags, it seems the whole FLAC files are transferred to my
client and back again to the server.

Doesn't it suffice just rewriting the header of the file containing the metadata?
Is it really necessary to rewrite the whole file?

As I don't have the slightest clue about the technical details when it comes
to writing tags to files, I actually might be wrong, but maybe some of the devs
or people with a little more knowledge of this topic could discuss, what to do
here.

Fact is: tagging FLAC (or other large files) through a slow link (such as WLAN)
is absolutely painful!
Maybe you'll find a smart way how to improve this.

Thanks a lot!
Elias P.


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On Sun, Sep 6, 2009 at 11:05 AM, Elias Probst<mail@...> wrote:

> Hi,
>
> I've noticed some trouble when re-tagging some of my FLAC albums using Amarok.
> Updating the tags of a single FLAC album takes up to 10 minutes, because my
> music collection is stored on a NFS share on my fileserver where I connect to
> via WLAN.
>
> When writing now the tags, it seems the whole FLAC files are transferred to my
> client and back again to the server.
>
> Doesn't it suffice just rewriting the header of the file containing the metadata?
> Is it really necessary to rewrite the whole file?
>
> As I don't have the slightest clue about the technical details when it comes
> to writing tags to files, I actually might be wrong, but maybe some of the devs
> or people with a little more knowledge of this topic could discuss, what to do
> here.

There is a padding block in FLAC files, that can be used for this
purpose. TagLib 1.5 and older doesn't know how to use this, and has to
resize the file every time. TagLib 1.6 (still to be released, there is
RC out) will use the padding block if it's there and is large enough
to hold the tags, so in most cases it will not need to resize the
file.

--
Lukas Lalinsky
lalinsky@...
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[eliasp]

On Sunday 06 September 2009 11:14:48 Lukáš Lalinský wrote:

> > As I don't have the slightest clue about the technical details when it
> > comes to writing tags to files, I actually might be wrong, but maybe some
> > of the devs or people with a little more knowledge of this topic could
> > discuss, what to do here.
>
> There is a padding block in FLAC files, that can be used for this
> purpose. TagLib 1.5 and older doesn't know how to use this, and has to
> resize the file every time. TagLib 1.6 (still to be released, there is
> RC out) will use the padding block if it's there and is large enough
> to hold the tags, so in most cases it will not need to resize the
> file.

Thanks a lot for this information - this is great news.
So I'm looking forward to the soon-to-be-released taglib 1.6.

Is 1.6 API compatible with 1.5? So will applications already using 1.5 still
work with 1.6? Or will I have to wait for updated applications?

Regards, Elias P.


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On Sun, Sep 6, 2009 at 11:23 AM, Elias Probst<mail@...> wrote:
> Thanks a lot for this information - this is great news.
> So I'm looking forward to the soon-to-be-released taglib 1.6.
>
> Is 1.6 API compatible with 1.5? So will applications already using 1.5 still
> work with 1.6? Or will I have to wait for updated applications?

Every 1.x release is API and ABI backward compatible. You can just
install new TagLib and applications will continue to work.

--
Lukas Lalinsky
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[eliasp]

On Sunday 06 September 2009 11:14:48 Lukáš Lalinský wrote:
> There is a padding block in FLAC files, that can be used for this
> purpose. TagLib 1.5 and older doesn't know how to use this, and has to
> resize the file every time. TagLib 1.6 (still to be released, there is
> RC out) will use the padding block if it's there and is large enough
> to hold the tags, so in most cases it will not need to resize the
> file.

Another question just came to my mind:
If a file doesn't have padding block yet, will taglib add one, when it has to
rewrite the whole file anyways?
So future tagging operations will just have to rewrite the padding block?

Regards, Elias P.


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On Sun, Sep 6, 2009 at 11:30 AM, Elias Probst<mail@...> wrote:

> On Sunday 06 September 2009 11:14:48 Lukáš Lalinský wrote:
>> There is a padding block in FLAC files, that can be used for this
>> purpose. TagLib 1.5 and older doesn't know how to use this, and has to
>> resize the file every time. TagLib 1.6 (still to be released, there is
>> RC out) will use the padding block if it's there and is large enough
>> to hold the tags, so in most cases it will not need to resize the
>> file.
>
> Another question just came to my mind:
> If a file doesn't have padding block yet, will taglib add one, when it has to
> rewrite the whole file anyways?
> So future tagging operations will just have to rewrite the padding block?

Correct, if there isn't a padding block yet (at all, or not large
enough), it will write at least 4096b large padding after the tag. So
next tag update should be quick again.

--
Lukas Lalinsky
lalinsky@...
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