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Topic: Remove cover art --> reduce file size? (Read 9832 times) previous topic - next topic
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Remove cover art --> reduce file size?

So, I took my FLAC collection and made an mp3 copy for portable use. That took a few days ...
For the FLACs -- being on TB drives --  size of embedded album art is really not an issue. For portable players, it is.

So, what if I
A) scripted an "extract to folder.jpg" (hm, what about .png?)
B) deleted the album art from the file

and optionally

C) all folder.jpg greater than size X are reduced. folder.jpg's are then embedded back to the mp3's.


Q1: How to ensure that mp3 file size does in fact shrink in step B)?
Q2: And maybe even, if step C) is applicable: How to ensure that mp3 file size does NOT shrink in step B), but DOES in step C)?
Q3: If I'd like to have a little bit of file padding though, just for the odd adjustment of formatting where Vorbis and ID3 are somewhat incompatible (... "AC/DC" ...), how do I?

Of course I don't want no audio transcoding.



(I have trouble searching for solutions to this, as "padding" seems to be used for audio when it comes to mp3.)

Remove cover art --> reduce file size?

Reply #1 –
Quote from: Porcus on
Q1: How to ensure that mp3 file size does in fact shrink in step B)?


  Does that have sense? Of course that removing the album art from the ID3v2 tag will make the file smaller. Yet, it is true that, if padding is kept, the file size won't change, but that's up to the tagger.

Quote from: Porcus on
Q2: And maybe even, if step C) is applicable: How to ensure that mp3 file size does NOT shrink in step B), but DOES in step C)?

If you don't remove the padding (which is the only thing that can make the file smaller), then changing the size of the album art itself won't change anything.


Quote from: Porcus on
Q3: If I'd like to have a little bit of file padding though, just for the odd adjustment of formatting where Vorbis and ID3 are somewhat incompatible (... "AC/DC" ...), how do I?

Why does the type of tags matter in this case? Are you adding ID3v2 tags to .ogg files? Are you adding VorbisComment to mp3 files? The tagger should take care of its size.


Quote from: Porcus on
Of course I don't want no audio transcoding.


Tagging does not affect the audio portion of the streams.


Quote from: Porcus on
(I have trouble searching for solutions to this, as "padding" seems to be used for audio when it comes to mp3.)

That's because you don't have to search for padding of mp3 files, but for padding of ID3v2 tags.

But just to clear the confusion:

An mp3 file is made of fixed size blocks (which represent the different CBR bitrates). Adding padding allows it to keep the sizes of these blocks constant, even if the data inside is not alway of fixed size. Usually, encoders use bit reservoir (which is using these bits for data of next block) instead of padding.

Padding on tags is reserving a space (whatever space specified) so that the tag block does not need to be rewritten. It is especially important when the tag is appended at the beginning of the file. And here is where the tagger program matters.

Remove cover art --> reduce file size?

Reply #2 –
Quote from: [JAZ] on
Of course that removing the album art from the ID3v2 tag will make the file smaller. Yet, it is true that, if padding is kept, the file size won't change, but that's up to the tagger.


My point exactly -- it's up to the software. So, how do I?


(When it comes to type of tag: The "/" is a reserved character in ID3, but not in Vorbis comments.)

Remove cover art --> reduce file size?

Reply #3 –
Quote from: Porcus on
For the FLACs,  size of embedded album art is really not an issue. For portable players, it is.


I'm curious what sort of image sizes, dimensions and formats we're talking about. Unless you have print-quality album art embedded in the files, how would it make a significant impact— especially as you're planning on putting a reduced version back into the file?

Remove cover art --> reduce file size?

Reply #4 –
Quote from: Porcus on
(When it comes to type of tag: The "/" is a reserved character in ID3, but not in Vorbis comments.)

I'm not sure what you mean.  My AC/DC mp3s have "/" in both v1 and v2.3 tags.

Remove cover art --> reduce file size?

Reply #5 –
I thought ID3 had really restrictive specifications on how big album art could be, so you couldn't even have large filesize album art wasting tons of space.

Remove cover art --> reduce file size?

Reply #6 –
What gave you that idea?  I just embedded a 15MB jpg into an mp3 file without any troubles.

Perhaps it is because mp3tag is not complying with some specification, but I highly doubt it.

Remove cover art --> reduce file size?

Reply #7 –
About size limits, that depends on the decoder, and if it knows how to skip non-audio data.
This is especially related to ID3 tags that go at the beginning. If the decoder doesn't know the ID3 tag, it has to search where the MP3 data starts. It might just read up to a specific amount of bytes, or get confused by data in the ID3 tag that could seem to be the start of the MP3 data. (at the end of the stream it matters too, but less).
There might be reasonable limits for some implementations. Obviously, it doesn't have sense that metadata (artwork) be bigger than the data (mp3 audio).

Remove cover art --> reduce file size?

Reply #9 –
The best I can figure from that discussion is a double back slash is used as a separator in mp3tag and that a forward slash may be interpreted as a separator in foobar2000.  I wouldn't try to divine any truth out of that discussion beyond how various programs may interpret them, especially as it may relate to a single forward slash.

FWIW, the versions of EAC, Winamp, iTunes, Lame, Tag, mp3tag and TagScanner that I use have absolutely no problem with a single forward slash.

EDIT: Reviewing the ID3v2.3.0 specification it does look as if the forward slash is to be used as a separator for various frames.  In light of this I'm glad to see that it isn't universally honored.

Remove cover art --> reduce file size?

Reply #10 –
Quote from: greynol on
What gave you that idea?  I just embedded a 15MB jpg into an mp3 file without any troubles.

Perhaps it is because mp3tag is not complying with some specification, but I highly doubt it.


I guess that's actually just a restriction in LAME (128KB).  Allegedly it's supposed to be removed in 3.99

Remove cover art --> reduce file size?

Reply #11 –
You can do it with latest version of TagScanner in one click.

Use internal Resize function for covers. You can change resolution and/or compression level of embedded pictures. All formats other than JPG will be converted to JPG.

File size will be adjustsed to new size of tag with mandatory padding at 1KB.