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FLAC tag and file size ?
Xrcr9709
post Feb 21 2012, 15:11
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Hello,

I just noticed that and at a first glance it looks weird to me.

I've encoded 11 FLAC files with FLAC Frontend. I've tagged them (without album cover), but I kept a copy of the untagged files.
When I compare their size, the tagged files and the non-tagged files have the exactly same size (in bytes).
(This changes of course if I add the album cover to the files.)

So why is that that add data to the file doesn't seem to make the file bigger ?
I guess I've used the standard tag files and maybe they have their place reserved even when they are empty ? Or something like that ?


Thank you for the info.
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basher
post Feb 25 2012, 23:06
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I have a question about tagging in FLAC files. I use the program Tagscanner for my tagging needs and I noticed something odd when I updated a few of the files with album art. The program shows you the bitrate and the compression ratio at the bottom right of the tagging window. When I added the album art, it increased the bitrate and the compression ratio. However, when I removed the album art, it kept the bitrate and ratio the same, which was odd because I expected it to revert back to the values before I added the art. I tried it in mp3Tag and that program showed me slightly different bitrate numbers which was odd because it should have shown the same numbers. Does this happen often to other people that tag FLAC files and if so, does this tagging information change the audio data in some way since the program is showing a difference in bitrate and compression ratio? Any clarification would be appreciated.

Thanks,
Basher
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JJZolx
post Feb 26 2012, 01:12
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QUOTE (basher @ Feb 25 2012, 15:06) *
When I added the album art, it increased the bitrate and the compression ratio. However, when I removed the album art, it kept the bitrate and ratio the same, which was odd because I expected it to revert back to the values before I added the art.


Many tagging programs, when you remove album art, will just put that space into the padding block instead of rewriting the whole file. Mp3tag also does this. It makes saving edits much faster.

QUOTE
I tried it in mp3Tag and that program showed me slightly different bitrate numbers which was odd because it should have shown the same numbers.


Bitrate may be calculated differently by the two programs. I'd suspect that one may use 10^6 as a megabit and the other may use 2^20.

QUOTE
Does this happen often to other people that tag FLAC files and if so, does this tagging information change the audio data in some way since the program is showing a difference in bitrate and compression ratio? Any clarification would be appreciated.


No, the audio data does not change. The reason that the bitrate and compression ratio change when you add the artwork is that they're both calculated based on the total file size vs. the uncompressed size of the audio data in the file. When the file size goes up because the metadata (or padding) size increases then the bitrate (often expressed as 'average bitrate') for the _file_ goes up.
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