Re: QTMetaDataGetNextItem -2177

Subject: Re: QTMetaDataGetNextItem -2177

From: Kevin Calhoun <email@hidden>

Date: Wed, 28 Mar 2007 13:53:22 -0700

Delivered-to: email@hidden

On Mar 28, 2007, at 12:07 PM, email@hidden wrote:

Does anyone else use QuickTime to fetch ID3 information from mp3 files?

I am coming across a large number of files which QuickTime apparently

cannot parse the metadata.

On a typical problem file:

-- Right-click "Get Info" shows the metadata exactly as I would love

to fetch it

-- iTunes shows the metadata exactly as I would love to fetch it

-- My code gets no metadata at all

Does this sound plausable, or am I doing something wrong when
requesting the metadata, or when instantiating the movie object?

You're doing nothing wrong. However, if you want the metadata exactly as "Get Info" delivers it, you can use CoreAudio's AudioFile API to do the job instead of QuickTime.

I know, this will probably come down to the specific file I am
working on.

Yes. The problem occur because the first frame of the ID3 tag is a picture that's larger than 500 KB, and QuickTime currently won't parse data in ID3 tags past a certain point, which is 96 KB on most systems. The result is a movie without any metadata.

In treating ID3v2 tags in this way QuickTime relies too much on a close reading of the ID3v2 specification, which says "it is desired that the frames are arranged in order of significance concerning the recognition of the file" and even provides an example of a reasonable ordering. However, the universe turns out to be capacious enough for ID3 tag editors that interpret the specification in a wide variety of ways, including one that goes to the trouble of writing frames within a tag according to the alphanumeric ordering of their identifiers. The identifiers for most of the interesting textual frames start with 'T', while the identifier for frames that store pictures is 'APIC', which is alphanumerically superior among defined frames to all but the relatively rare "audio encryption" frame ('AENC'). So pictures take a place of preeminence in tags written by that particular editor. (I won't say which editor it is, except that it costs $39 more than my favorite ID3 tag editor.)

I would like to see this problem resolved in a future release of QuickTime, so please report this as a QuickTime bug and make a couple of the problematic files available.

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