Topic: Average Compression Ratio: 0.2754 Whaaa?!!

[ford prefect]

Just extracted and FLAC'd some 2002 Europe Ratdog shows I got in the mail.  Here's an example of the before/after filesizes (MB's):

WAVE | FLAC
-----------
45.9 | 12.2
85.6 | 23.8
72.2 | 19.8

Wholeshow WAVE: 1761MB
Wholeshow FLAC: 462MB   

I set FLAC compression to level 8 - like I always do.

SHNtool tells me that the average compression ratio for the show is 0.2754 - Prior to this, I don't think I've ever seen a ratio less than .55 - what could cause this?!  Should I be concerned?  Jeez, 3 disc show that now fits on a single data disc.

Thanks

    length     expanded size   cdr  WAVE problems filename
     4:20.28       45929900    ---   --   ---xx   ratdog2002-06-28d1t01.flac
     8:05.42       85652828    ---   --   ---xx   ratdog2002-06-28d1t02.flac
     6:49.35       72229964    ---   --   ---xx   ratdog2002-06-28d1t03.flac
     4:16.42       45257228    ---   --   ---xx   ratdog2002-06-28d1t04.flac
     7:29.23       79257740    ---   --   ---xx   ratdog2002-06-28d1t05.flac
     6:48.59       72110012    ---   --   ---xx   ratdog2002-06-28d1t06.flac
     8:45.12       92638268    ---   --   ---xx   ratdog2002-06-28d1t07.flac
     7:00.03       74095100    ---   --   ---xx   ratdog2002-06-28d1t08.flac
     2:35.69       27504332    ---   --   ---xx   ratdog2002-06-28d1t09.flac
     7:20.49       77731292    ---   --   ---xx   ratdog2002-06-28d1t10.flac
     4:02.07       42705308    ---   --   ---xx   ratdog2002-06-28d1t11.flac
     4:57.62       52536668    ---   --   ---xx   ratdog2002-06-28d2t01.flac
     8:00.29       84740252    ---   --   ---xx   ratdog2002-06-28d2t02.flac
     7:23.61       78288716    ---   --   ---xx   ratdog2002-06-28d2t03.flac
     9:11.35       97278764    ---   --   ---xx   ratdog2002-06-28d2t04.flac
    10:16.32      108737708    ---   --   ---xx   ratdog2002-06-28d2t05.flac
     9:16.11       98104316    ---   --   ---xx   ratdog2002-06-28d2t06.flac
     9:17.07       98271308    ---   --   ---xx   ratdog2002-06-28d2t07.flac
     8:14.30       87212204    ---   --   ---xx   ratdog2002-06-28d2t08.flac
     2:48.29       29703452    ---   --   ---xx   ratdog2002-06-28d3t01.flac
    15:44.36      166606316    ---   --   ---xx   ratdog2002-06-28d3t02.flac
     4:53.15       51720524    ---   --   ---xx   ratdog2002-06-28d3t03.flac
     1:52.19       19801532    ---   --   ---xx   ratdog2002-06-28d3t04.flac
     1:14.30       13124204    ---   --   ---xx   ratdog2002-06-28d3t05.flac
     5:43.72       60674588    ---   --   ---xx   ratdog2002-06-28d3t06.flac
   166:28.12     1761912524 B                     (totals for 25 files, 0.2754 overall compression ratio)

[JasonSobel]

that is very high compression.  with FLAC, a lot of it depends on the levels.  my "stage banter" tracks always get a compression ratio of around .3
So what are the levels like?  is the recording a very quiet recording?

if that's not it, I'm not sure what's going on.

[dnsacks]

was this a stereo recording?  Flac will detect a mono recording (same info on each channel) and will compress down to a single channel, which could also cause your very high compression level.

[OFOTD]

Someone may have this but I remember back a few years ago when FLAC was starting to penetrate the SHN world that someone had done a comaprison of the different compression levels and found that there was minimal difference size wise between Level 6 and Level 8.  I have always just used 6 because it is quite a bit faster to encode and I held the belief that the size differnece was tiny. 

Anyone have any other info?

[F.O.Bean]

Someone may have this but I remember back a few years ago when FLAC was starting to penetrate the SHN world that someone had done a comaprison of the different compression levels and found that there was minimal difference size wise between Level 6 and Level 8. I have always just used 6 because it is quite a bit faster to encode and I held the belief that the size differnece was tiny.

Anyone have any other info?

ive done this test and can verify your statement

doing about 1GB of data, i saved about 1-2MB VERY minimal IMO, and 6 is SOOO much faster

[Chad817]

that is very high compression.  with FLAC, a lot of it depends on the levels.  my "stage banter" tracks always get a compression ratio of around .3
So what are the levels like?  is the recording a very quiet recording?

if that's not it, I'm not sure what's going on.

this would be my guess as well..I've only seen levels like that on "intro" tracks or very quiet passages.

[OFOTD]

Someone may have this but I remember back a few years ago when FLAC was starting to penetrate the SHN world that someone had done a comaprison of the different compression levels and found that there was minimal difference size wise between Level 6 and Level 8. I have always just used 6 because it is quite a bit faster to encode and I held the belief that the size differnece was tiny.

Anyone have any other info?

ive done this test and can verify your statement

doing about 1GB of data, i saved about 1-2MB VERY minimal IMO, and 6 is SOOO much faster

Thanks Bean! +T    6 is SHOCKINGLY faster compared to level 8

I was wonderingif that was still true as I am not following the bleeding edge of FLAC these days.

[ford prefect]

that is very high compression.  with FLAC, a lot of it depends on the levels.  my "stage banter" tracks always get a compression ratio of around .3
So what are the levels like?  is the recording a very quiet recording?

Yup, that seems to be it - recording is definitely very quiet.  I don't have SF or WaveLab here at work to get the exact numbers on it, but looking at it in CD Wave shows low levels.  Anyone know what that "Dynamics" section indicates?  (attached a pic from 1 of the tracks)

Thanks for the responses! +T

[ford prefect]

Someone may have this but I remember back a few years ago when FLAC was starting to penetrate the SHN world that someone had done a comaprison of the different compression levels and found that there was minimal difference size wise between Level 6 and Level 8. I have always just used 6 because it is quite a bit faster to encode and I held the belief that the size differnece was tiny.

Anyone have any other info?

ive done this test and can verify your statement

doing about 1GB of data, i saved about 1-2MB VERY minimal IMO, and 6 is SOOO much faster

Hmm.. I think it depends on the recording - I tried this a year or 2 ago with multiple seeds, some soundboard and some audience, and usually saved about 20-30MB's between level 6 and level 8.  The room for a few xtra shows on my hard drive convinced me to use level 8.

[Krispy D]

being a total n00b I've always compressed to flac level 5 just cause it seemed like what I saw on archive the most.  Is this wrong?  should I be using level 6?  I just assumed 8 was more compresion and 1 was the least.  and 5 seemed like good midle ground.  from this thread it sounds like the opposite is true?  are you guys compressing different tracks at different levels?


just when I felt like I was starting to know what I was doing...
please direct me my all knowing taper family...

kris

[ford prefect]

I just assumed 8 was more compresion and 1 was the least.  

This is correct, 8 will give you the smallest files but will take the longest to encode/decode.  1 will give you the largest files, but will take the least time to encode/decode.

There's no wrong way, just personal preferences.  I don't think I've seen anyone use levels 1 through 3.

I always compress the whole show at a single level, it's too much work to pick and choose which tracks get which levels.

[ford prefect]

Hmm.. I think it depends on the recording - I tried this a year or 2 ago with multiple seeds, some soundboard and some audience, and usually saved about 20-30MB's between level 6 and level 8.  The room for a few xtra shows on my hard drive convinced me to use level 8.

Just tried it with the above Ratdog show and saved only 3MB though.   

[itook2much]

I always use level 8.  even if it's just a few MB, it saves space.  And although it takes a little more time to encode, it doesn't take any longer to decode.

[Krispy D]

thanks ford prefect...

for the reassurance that I might almost know what I'm doing!!  so it's just about size for storarage right?  I mean lossless is lossless.  The decoded end result is the same right?

[ford prefect]

so it's just about size for storarage right?  I mean lossless is lossless.  The decoded end result is the same right?

Yessir.  And it's also about speed for the decode.  Levels 5 and 6 will decode slightly faster than level 8.  Inverse relationship between speed of the decode and size of the files.

In the end, regardless of what level you use, the wave files will decode identically.  Like you said, it's all lossless.