Does Play change metadata on import?

Discuss Play, an open source multi-format audio player.
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santino
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Does Play change metadata on import?

Post by santino » Sun Sep 20, 2009 1:55 am

Interesting observation with metadata and bitrates. I added a bunch of iTunes Plus (256bit AAC, VBR) tracks to my Play library. Play shows bitrate as "unknown" which is odd, but more interesting is if I look at the tracks back in iTunes, it now shows the true VBR bitrate of the track instead of the target 256. Also, iTunes shows the track as encoded by Play. It doesn't look like Play is re-encoding anything, so does it just change the metadata by default on import to show Play as the encoder with the true bitrate?

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sbooth
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Re: Does Play change metadata on import?

Post by sbooth » Mon Sep 21, 2009 12:57 am

When a file is added to the library Play doesn't do any writing of metadata. If you want to do an experiment I would be curious to see a diff of a duplicate file once added to Play against the original which wasn't added.

I can't explain why the bitrate would seem to change in iTunes- I will take a look at Play's source and see if I can see anything.

santino
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Re: Does Play change metadata on import?

Post by santino » Mon Sep 21, 2009 11:46 am

The bitrate itself doesn't change, just the advertised bitrate. iTunes will only show the "target" bitrate for any track, so if it is VBR encoded (like iTunes Plus tracks) you don't see the real bitrate, just the target 256. For some reason moving a track into the Play library gets iTunes to show the real bitrate instead. Personally, I like this as it was always one of my annoyances with iTunes, I just don't get why it happens. All run a diff and see what it looks like.

santino
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Re: Does Play change metadata on import?

Post by santino » Wed Sep 23, 2009 3:22 pm

So, it looks like I forgot that I applied ReplayGain to the tracks I added to the library which explains why they show up in iTunes as encoded by Play. How bitrate is reported is still a bit of a mystery to me though. If I purchase a song from the iTunes Store (256 AAC VBR), iTunes shows the bitrate as "256 kbps" Play shows the bitrate as "unknown", and after I apply ReplayGain, iTunes will show the true bitrate - "252 kbps" and Play still shows it as "unknown". If I encode my own CDs as iTunes Plus (again 256 AAC VBR), iTunes shows these as "256 kbps (VBR)" whether Play applies ReplayGain or not, Play still shows "unknown".

All of this is superficial. I'm just curious why the tagging behaves differently in iTunes (more a question for Apple I guess) and why Play doesn't seem to understand AAC VBR, but obviously plays it back just fine.

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sbooth
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Re: Does Play change metadata on import?

Post by sbooth » Wed Sep 23, 2009 4:26 pm

This is probably because of the the "Encoding Params" metadata atom that iTunes sets and Play does not. I need to add code to Play to do this for AAC files- I've just done it for Max and iTunes displays the bitrate correctly for Max-generated AAC files now.

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