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Lavf VS LibFLAC
fehers
post Nov 15 2012, 20:50
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Okay i converted .m4a file to .flac using FFMPEG like...

ffmpeg -i filename.m4a filename.flac

Using spectro analizer to see the file I noticed the one converted with ffmpeg has compression type of "Lavf54.36.100" while all the others on my computer downloaded from different sources have "LibFLAC 1.2.1". I checked this with at least 20 different flac files from different albums and sources. So my question is what is this "Lavf54.36.100" when all other I checked have "LibFLAC 1.2.1"?

Screenshots here!
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saratoga
post Nov 15 2012, 20:54
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Lavf is part of ffmpeg, so that tag means you've encoded the file with ffmpeg.
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Kohlrabi
post Nov 15 2012, 22:43
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QUOTE (fehers @ Nov 15 2012, 21:50) *
Okay i converted .m4a file to .flac using FFMPEG like...

ffmpeg -i filename.m4a filename.flac

Using spectro analizer to see the file
I hope the .m4a files in question were ALAC and not AAC, since a conversion from lossy to lossless would be insanely wasteful and pointless. Also, A better way than spectrograms to ensure that your encoder was lossless is to bit-compare the decoded PCM data stream. For example, foo_bitcompare for foobar2000 allows to compare two decoded streams with each other.

This post has been edited by Kohlrabi: Nov 15 2012, 22:44


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fehers
post Nov 16 2012, 00:48
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QUOTE (saratoga @ Nov 15 2012, 20:54) *
Lavf is part of ffmpeg, so that tag means you've encoded the file with ffmpeg.


IC! So it's kinda like a "signature" of the software trough which the file was created and not the encoder version itself or something like that... Thanks!
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saratoga
post Nov 16 2012, 00:54
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QUOTE (fehers @ Nov 15 2012, 19:48) *
QUOTE (saratoga @ Nov 15 2012, 20:54) *
Lavf is part of ffmpeg, so that tag means you've encoded the file with ffmpeg.


IC! So it's kinda like a "signature" of the software trough which the file was created and not the encoder version itself or something like that...


No, its the version and name of the encoder used.
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fehers
post Nov 16 2012, 01:12
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QUOTE (Kohlrabi @ Nov 15 2012, 22:43) *
I hope the .m4a files in question were ALAC and not AAC, since a conversion from lossy to lossless would be insanely wasteful and pointless. Also, A better way than spectrograms to ensure that your encoder was lossless is to bit-compare the decoded PCM data stream. For example, foo_bitcompare for foobar2000 allows to compare two decoded streams with each other.

Yes, they were ALAC i'm quite sure but thanks for the link I'll be definitely using that but... if a file was converted from MP3 to FLAC and then from FLAC to APE...

There are a lot of idiots out there! I was downloading "Amnezia Super Hits 75" from xxxx in FLAC format. When I was listening to the tracks I noticed the files sound like mp3. Using a spectrogram I found that every file missed the 20 - 22 khz range which means they were definitely reconverted to lossless... I know you wouldn't tell for sure from one track only especially from vinyl rips or older tracks but these are all 2012 music from many different providers and studios...

You'd be surprised how many fake lossless files are out there. This for example is also a fake in my opinion. Also missing the higher spectrum. Try to download one part only, extract and see (hear) for yourself...

This post has been edited by greynol: Nov 16 2012, 04:56
Reason for edit: TOS #9 violation
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fehers
post Nov 16 2012, 01:29
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QUOTE (saratoga @ Nov 16 2012, 00:54) *
No, its the version and name of the encoder used.



Then I don't get it! You say "that tag means you've encoded the file with ffmpeg". Yes, with ffmpeg but I'm assuming ffmpeg is using the "FLAC sources" to do that and not just any codec...

The file with the info "Lavf54.36.100" I'm talking about has a .flac extension...

This post has been edited by fehers: Nov 16 2012, 01:49
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saratoga
post Nov 16 2012, 02:51
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I don't know why you would assume that. Ffmpeg does not use the flac source.
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Heliologue
post Nov 16 2012, 03:41
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QUOTE (fehers @ Nov 15 2012, 19:29) *
The file with the info "Lavf54.36.100" I'm talking about has a .flac extension...


The term "FLAC" is commonly used both for the file format (a lossless audio codec) and the compression program itself. An easy way to think about it is to compare it to ZIP files. Whether they're made with WinZip, WinRAR, InfoZip, 7-Zip, etc, they all create the same file format.

Both libFLAC and ffmpeg (and FLACCL and &c.) create files that follow the FLAC specification. This means (A) the files are lossless compressions of the source file and (B) they can be decoded by any decompressor that adheres to the standard.
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