weird FLAC compression

bjoker · 11th August 2020, 18:47

Hi,

I have a PCM file - LPCM Audio / 2.0 / 48 kHz / 1536 kbps / 16-bit

Encoded with 2 FLAC versions and the outputs are

1) libFLAC 1.2.1 (using eac3to)

Quote:

General
Complete name : XXX_Main.flac
Format : FLAC
Format/Info : Free Lossless Audio Codec
File size : 278 MiB
Duration : 1 h 43 min
Overall bit rate mode : Variable
Overall bit rate : 376 kb/s

Audio
Format : FLAC
Format/Info : Free Lossless Audio Codec
Duration : 1 h 43 min
Bit rate mode : Variable
Bit rate : 376 kb/s
Channel(s) : 2 channels
Channel positions : Front: L R
Sampling rate : 48.0 kHz
Bit depth : 16 bits
Stream size : 278 MiB (100%)
Writing library : libFLAC 1.2.1 (UTC 2007-09-17)

2) libFLAC 1.3.2 CLI (tried with & without "--compression-level-5" option to check default compression level. both resulted same)

Quote:

General
Complete name : XXX_Main_flac_WSL_level5.flac
Format : FLAC
Format/Info : Free Lossless Audio Codec
File size : 883 MiB
Overall bit rate mode : Variable
Overall bit rate : 1 195 b/s

Audio
Format : FLAC
Format/Info : Free Lossless Audio Codec
Bit rate mode : Variable
Bit rate : 1 194 b/s
Channel(s) : 2 channels
Channel positions : Front: L R
Sampling rate : 48 Hz
Bit depth : 16 bits
Stream size : 882 MiB (100%)
Writing library : libFLAC 1.3.2 (UTC 2017-01-01)

I totally get it if the difference is like 10-20% but it's almost 300% difference. Could anyone advise what's wrong (if any) here?

Thanks!

nevcairiel · 11th August 2020, 19:46

Is your FLAC build with Visual Studio and 64-bit? There has been an odd bug that caused files to barely compress when Visual Studio compiles libFLAC in 64-bit mode. Newer libFLAC has a work-around for this issue, ie. you could get 1.3.3

bjoker · 11th August 2020, 20:40

Thanks nevcairiel for the reply.

I just tried 1.3.3 from https://www.videohelp.com/software/FLAC-Encoder (win64-bit) but same result (bloated flac).

Quote:

General
Complete name : XXX_Main_flac_133_win64.flac
Format : FLAC
Format/Info : Free Lossless Audio Codec
File size : 883 MiB
Overall bit rate mode : Variable
Overall bit rate : 1 195 b/s

Audio
Format : FLAC
Format/Info : Free Lossless Audio Codec
Bit rate mode : Variable
Bit rate : 1 194 b/s
Channel(s) : 2 channels
Channel positions : Front: L R
Sampling rate : 48 Hz
Bit depth : 16 bits
Stream size : 882 MiB (100%)
Writing library : libFLAC 1.3.3 (UTC 2019-08-04)

tebasuna51 · 11th August 2020, 22:39

A wav 1 h 43 min at 1536 kbps (2.0, 48000, 16bit) have a size of 1.2 GB, a flac compression to 882 MB is more or less normal (73%), a compression to 278 MB is not normal (23%). A tipical compression can be 60%.

The source have many silences to justify this 23%?

bjoker · 12th August 2020, 15:34

Quote:

Originally Posted by tebasuna51

A wav 1 h 43 min at 1536 kbps (2.0, 48000, 16bit) have a size of 1.2 GB, a flac compression to 882 MB is more or less normal (73%), a compression to 278 MB is not normal (23%). A tipical compression can be 60%.

The source have many silences to justify this 23%?

Yeah it is audio of a very old movie with lot of silences.

But how come the very old version of FLAC compresses a lot more ( 23% vs 73%) than the latest FLAC version? I'm able to reverse the flac file back to PCM and hash check (they matched) for both versions.

tebasuna51 · 12th August 2020, 18:11

I can't confirm than v1.2.1 compress more.
With 1 hour wav (from Jurassic Park) test:

Code:

                            Size (bytes)  enc. time   %
-------------------------  -------------  --------- ------
WAV 5.1,1 hour,48kHz,24 b  3.110.400.102     -
flac.exe -5    1.3.3 64 b  1.708.546.600     22,68  54,930
flac.exe -5 -e 1.3.3 64 b  1.707.631.271     45,34  54,901
ffmpeg   -5 Lavf58.42.100  1.707.221.663     23,63  54,887
eac3to libflac 1.2.1 32 b  1.705.970.954   3:43,90  54,847
flac.exe -8    1.3.3 64 b  1.705.443.722     38,95  54,830
flac.exe -8 -e 1.3.3 64 b  1.705.443.722     43,39  54,830
eac3to libflac 1.3.3 32 b  1.705.367.448   1:19,47  54,828
ffmpeg  -12 Lavf58.42.100  1.704.010.142   5:16,12  54,784

there are very little differences but seems better 1.3.3.
I used best size (-8 in flac.exe), if I remember ok madshi use also -8 by default.

with ffmpeg I used -compression_level 12, I don't know how reproduce that with flac, we obtain the best size (only a 0,05 % better) but with huge encoding time.

EDIT: more encode options.
If default for flac and ffmpeg (compression level 5) is more compatible with hardware players, like SeeMoreDigital say, I think is the best option because the gain in size is only a 0,1 %

lvqcl · 12th August 2020, 21:03

You can add -e option
For example, flac.exe -5 -e in.wav -o out.flac

tebasuna51 · 13th August 2020, 09:55

Same size with -8 -e:

Code:

flac.exe -8    1.3.3 64 b  1.705.443.722     38,95  54,830
flac.exe -8 -e 1.3.3 64 b  1.705.443.722     43,39  54,830
flac.exe -5 -e 1.3.3 64 b  1.707.631.271     45,34  54,901
flac.exe -5    1.3.3 64 b  1.708.546.600     22,68  54,930

BTW minimal differences don't justify spend more time encoding.
Flac.exe -8 is a good option for me.

Of course I don't know for what libflac 1.2.1 32 bits compress the bjoker file with a 23%

SeeMoreDigital · 13th August 2020, 10:36

For anyone who is interested...

The 'Compression 5' setting is more compatible with hardware playback devices

bjoker · 13th August 2020, 11:25

I encoded atleast 50 PCMs to FLAC and the difference has always been <20% between 1.2.1 & 1.3.2 but this one is different.
Not sure what compression level does eac3to use (I think it is 5) but I used default setting. I tried 1.3.2 (& 1.3.3) with default & "--compression-level-5" but same result.
There seems to be no way of finding the compression level of a FLAC file.

Could i upload the whole audio (or part of it) to a file hoster and share here so anyone with interest could reproduce the problem?

Thanks everyone for your replies

tebasuna51 · 13th August 2020, 11:58

@SeeMoreDigital
Good to know, I modified the table with the comparative.

I I will modify the default for encode to flac with ffmpeg in Useac3to GUI.

@bjoker
Don't upload the file for me, I believe in your test and I can't do anything more with it.

The eac3to compression level is the max (I suppose 8) like madshi say here

Boulder · 13th August 2020, 12:38

If you post the issue at https://sourceforge.net/p/flac/bugs/ , maybe some dev will be able to see what the difference between the files is. As far as I've understood, eac3to uses a standard library for FLAC so it should be possible to reproducible with a build from the same sources.

11th August 2020, 19:46	#2 \| Link
nevcairiel Registered Developer Join Date: Mar 2010 Location: Hamburg/Germany Posts: 10,346	Is your FLAC build with Visual Studio and 64-bit? There has been an odd bug that caused files to barely compress when Visual Studio compiles libFLAC in 64-bit mode. Newer libFLAC has a work-around for this issue, ie. you could get 1.3.3 __________________ LAV Filters - open source ffmpeg based media splitter and decoders

11th August 2020, 22:39	#4 \| Link
tebasuna51 Moderator Join Date: Feb 2005 Location: Spain Posts: 6,914	A wav 1 h 43 min at 1536 kbps (2.0, 48000, 16bit) have a size of 1.2 GB, a flac compression to 882 MB is more or less normal (73%), a compression to 278 MB is not normal (23%). A tipical compression can be 60%. The source have many silences to justify this 23%? __________________ BeHappy, AviSynth audio transcoder. Last edited by tebasuna51; 11th August 2020 at 22:46.

12th August 2020, 18:11	#6 \| Link
tebasuna51 Moderator Join Date: Feb 2005 Location: Spain Posts: 6,914	I can't confirm than v1.2.1 compress more. With 1 hour wav (from Jurassic Park) test: Code: Size (bytes) enc. time % ------------------------- ------------- --------- ------ WAV 5.1,1 hour,48kHz,24 b 3.110.400.102 - flac.exe -5 1.3.3 64 b 1.708.546.600 22,68 54,930 flac.exe -5 -e 1.3.3 64 b 1.707.631.271 45,34 54,901 ffmpeg -5 Lavf58.42.100 1.707.221.663 23,63 54,887 eac3to libflac 1.2.1 32 b 1.705.970.954 3:43,90 54,847 flac.exe -8 1.3.3 64 b 1.705.443.722 38,95 54,830 flac.exe -8 -e 1.3.3 64 b 1.705.443.722 43,39 54,830 eac3to libflac 1.3.3 32 b 1.705.367.448 1:19,47 54,828 ffmpeg -12 Lavf58.42.100 1.704.010.142 5:16,12 54,784 there are very little differences but seems better 1.3.3. I used best size (-8 in flac.exe), if I remember ok madshi use also -8 by default. with ffmpeg I used -compression_level 12, I don't know how reproduce that with flac, we obtain the best size (only a 0,05 % better) but with huge encoding time. EDIT: more encode options. If default for flac and ffmpeg (compression level 5) is more compatible with hardware players, like SeeMoreDigital say, I think is the best option because the gain in size is only a 0,1 % __________________ BeHappy, AviSynth audio transcoder. Last edited by tebasuna51; 13th August 2020 at 11:54. Reason: add info

13th August 2020, 09:55	#8 \| Link
tebasuna51 Moderator Join Date: Feb 2005 Location: Spain Posts: 6,914	Same size with -8 -e: Code: flac.exe -8 1.3.3 64 b 1.705.443.722 38,95 54,830 flac.exe -8 -e 1.3.3 64 b 1.705.443.722 43,39 54,830 flac.exe -5 -e 1.3.3 64 b 1.707.631.271 45,34 54,901 flac.exe -5 1.3.3 64 b 1.708.546.600 22,68 54,930 BTW minimal differences don't justify spend more time encoding. Flac.exe -8 is a good option for me. Of course I don't know for what libflac 1.2.1 32 bits compress the bjoker file with a 23% __________________ BeHappy, AviSynth audio transcoder. Last edited by tebasuna51; 13th August 2020 at 10:23.

13th August 2020, 10:36	#9 \| Link
SeeMoreDigital Life's clearer in 4K UHD Join Date: Jun 2003 Location: Notts, UK Posts: 12,227	For anyone who is interested... The 'Compression 5' setting is more compatible with hardware playback devices __________________ \| I've been testing hardware media playback devices and software A/V encoders and decoders since 2001 \| My Network Layout & A/V Gear \|

12th August 2020, 21:03	#7 \| Link
lvqcl Registered User Join Date: Aug 2015 Posts: 294	You can add -e option For example, flac.exe -5 -e in.wav -o out.flac

13th August 2020, 11:25	#10 \| Link
bjoker Registered User Join Date: Jan 2013 Posts: 50	I encoded atleast 50 PCMs to FLAC and the difference has always been <20% between 1.2.1 & 1.3.2 but this one is different. Not sure what compression level does eac3to use (I think it is 5) but I used default setting. I tried 1.3.2 (& 1.3.3) with default & "--compression-level-5" but same result. There seems to be no way of finding the compression level of a FLAC file. Could i upload the whole audio (or part of it) to a file hoster and share here so anyone with interest could reproduce the problem? Thanks everyone for your replies

13th August 2020, 11:58	#11 \| Link
tebasuna51 Moderator Join Date: Feb 2005 Location: Spain Posts: 6,914	@SeeMoreDigital Good to know, I modified the table with the comparative. I I will modify the default for encode to flac with ffmpeg in Useac3to GUI. @bjoker Don't upload the file for me, I believe in your test and I can't do anything more with it. The eac3to compression level is the max (I suppose 8) like madshi say here __________________ BeHappy, AviSynth audio transcoder. Last edited by tebasuna51; 13th August 2020 at 12:07. Reason: add info

13th August 2020, 12:38	#12 \| Link
Boulder Pig on the wing Join Date: Mar 2002 Location: Finland Posts: 5,729	If you post the issue at https://sourceforge.net/p/flac/bugs/ , maybe some dev will be able to see what the difference between the files is. As far as I've understood, eac3to uses a standard library for FLAC so it should be possible to reproducible with a build from the same sources. __________________ And if the band you're in starts playing different tunes I'll see you on the dark side of the Moon...

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