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7z beats other codecs on 24bit 48khz sample, Split from: "Which is the best lossless codec?"
Dave_Scream
post Aug 17 2013, 09:55
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I just lold ))
flac highest 610 -> 377
monkey's insane 610 -> 375
7zip 610 -> 211

Use 7zip guys )))
---
UPD. added Monkeys audio

This post has been edited by Dave_Scream: Aug 17 2013, 10:06
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Propheticus
post Aug 17 2013, 10:41
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Have you tried zipping the flac or other codecs? The comparison is not totally fair now as zip is no audio codec. It cant be played back directly or seeked ahead in. It needs to be unpacked to memory or temp file in full before the enclosed data can be played. The other formats can be played from halfway the file without decoding the whole file first.
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Dave_Scream
post Aug 17 2013, 10:56
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QUOTE (Propheticus @ Aug 17 2013, 03:41) *
Have you tried zipping the flac or other codecs? The comparison is not totally fair now as zip is no audio codec. It cant be played back directly or seeked ahead in. It needs to be unpacked to memory or temp file in full before the enclosed data can be played. The other formats can be played from halfway the file without decoding the whole file first.

Hello.
Zipping already compressed things is bad idea)

Yes, you're right, but I was surprised that 7zip, which used for common compression, got better results than most popular audio compression codecs on their highest settings. And 7zip is not just better, it have ~55 - 75% bonus in file size.

For me, lossless is only for archive needs. For listening needs I have lossy codecs, because my SD card or flash card in my phone dosent have so much space.

I think peoples like me, who need lossless for archive needs must think about this moment)
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Propheticus
post Aug 17 2013, 11:06
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I can see how this is interesting for purely archiving purposes. It not that surprising though. The zipping can use much large blocks and compress patterns throughout the file, while an audio codec must use smaller blocks (sequentially) to be realtime decodeable and playable.
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Jan S.
post Aug 17 2013, 11:25
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I fail to see how this is interesting that you found one file where 7z wins.

I tried on an album:
wav: 678MB
7z: 572MB
rar: 373MB
wv: 255MB


I would take any wager on general compressors losing that battle 95%+ of the time.
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lvqcl
post Aug 17 2013, 11:30
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My test:

WAV 16/44: 569 743 820 bytes
7z LZMA Ultra: 529 341 057 bytes
RAR5 Best: 427 763 395 bytes
FLAC -8: 362 224 323 bytes
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Dave_Scream
post Aug 17 2013, 11:31
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QUOTE (Jan S. @ Aug 17 2013, 04:25) *
I fail to see how this is interesting that you found one file where 7z wins.

I tried on an album:
wav: 678MB
7z: 572MB
rar: 373MB
wv: 255MB


I would take any wager on general compressors losing that battle 95%+ of the time.

strange. maybe its because I used 24bit 48khz wav input? and lossless codecs are not optimized good to compress >22khz frequencies? so pure math of 7z make it winner?
here is the link to my test file http://yadi.sk/d/hpGxgr9y8-z1e
and here is spectrogramm that shows that frequencies >22khz available


This post has been edited by Dave_Scream: Aug 17 2013, 11:33
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TBeck
post Aug 17 2013, 13:54
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QUOTE (Dave_Scream @ Aug 17 2013, 12:31) *
strange. maybe its because I used 24bit 48khz wav input? and lossless codecs are not optimized good to compress >22khz frequencies? so pure math of 7z make it winner?
here is the link to my test file http://yadi.sk/d/hpGxgr9y8-z1e

One possible explaination: Quite few of the possible sample values between the files minimum and maximum value are present in the file. That's nice for general purpose file compressors.

Some possible reasons:

- Amplification by a quite large factor
- Companded source signal (a-law, u-law etc.)

The resulting sample distribution then contains a lot of holes.

While some audio compressor can detect an amplification by an integer power of 2 (the wasted bits feature), to my knowledge only OptimFrog's experimental mode can take advantage of other transformations.

I tried it. Because this feature currently only works for 16 bit samples, i converted your file to 16 bit / 96 khz (without dithering).

Results:

Optimfrog Normal: 41.87 % (of the uncompressed file size)
Optimfrog Normal -- experimental: 29.46 %

This seems to support my hypothesis.

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saratoga
post Aug 18 2013, 03:51
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QUOTE (Propheticus @ Aug 17 2013, 06:06) *
I can see how this is interesting for purely archiving purposes. It not that surprising though. The zipping can use much large blocks and compress patterns throughout the file, while an audio codec must use smaller blocks (sequentially) to be realtime decodeable and playable.


Since 7zip doesn't know about stereo, I expect that for anything but mono audio or two uncorrelated stereo channels, a regular lossless codec will have a pretty big advantage since it can do M/S stereo.
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Thundik81
post Aug 18 2013, 10:54
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QUOTE (Jan S. @ Aug 17 2013, 03:25) *
I fail to see how this is interesting that you found one file where 7z wins.

I tried on an album:
wav: 678MB
7z: 572MB
rar: 373MB
wv: 255MB


I would take any wager on general compressors losing that battle 95%+ of the time.


http://www.squeezechart.com/audio.html
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Nystagmus
post Nov 10 2013, 22:17
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Although not directly related to this conversation, it may be useful to know that foobar2000 has a component add on that allows for playing soundfiles embedded in 7z archives without needing to manually decompress them.


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kode54
post Nov 11 2013, 02:37
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Yes, and that component decompresses the entire file to memory before playing it.
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Seren
post Nov 11 2013, 19:40
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I was wondering... does it work out better if you compress the wav with or the already compressed flac/ape ect with 7z. I'd love to try it but I have to get some sleep now =(
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xnor
post Nov 11 2013, 20:25
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QUOTE (Seren @ Nov 11 2013, 20:40) *
I was wondering... does it work out better if you compress the wav with or the already compressed flac/ape ect with 7z. I'd love to try it but I have to get some sleep now =(


Well, one album I tested (metal album, released 2013, with low dynamic range) compressed to:

wav: 484 MB (uncompressed)
flac: 344 MB (level 8)
wav->7z: 468 MB (ultra)
flac->7z: 344 MB (level 8, ultra)

So basically just a waste of time and resources.

Since compression algorithms make the compressed data more random further compression can only squeeze out a few more bytes, or if the initial compression was done well actually increase the size (so a waste of time, resources, and disk space).

This post has been edited by xnor: Nov 11 2013, 20:26
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pdq
post Nov 11 2013, 21:41
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On the other hand, since WinZip can compress with the WavPack compression algorithm, it will compress wav files quite efficiently.
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kode54
post Nov 12 2013, 02:42
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And only WinZip can unpack those.
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probedb
post Nov 12 2013, 12:52
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Also bear in mind 7-zip isn't actively developed, it hasn't had a stable (non alpha/beta) release since 2010.
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xnor
post Nov 12 2013, 14:14
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QUOTE (probedb @ Nov 12 2013, 13:52) *
Also bear in mind 7-zip isn't actively developed, it hasn't had a stable (non alpha/beta) release since 2010.

Then why did the developer announce a new alpha release in the coming days? dry.gif

It's still being actively developed, there's just not much to fix especially in the stable version.

This post has been edited by xnor: Nov 12 2013, 14:15
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(Sly)
post Nov 12 2013, 18:28
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By the way 7-zip LZMA Ultra uses 64 MB dictionary size, that helps a lot, lossless audio codecs cannot exist with a dictionary size this huge, it would make seeking almost impossible.

This post has been edited by (Sly): Nov 12 2013, 18:28


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bryant
post Nov 12 2013, 19:24
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I took a look at this file, and as Thomas says, the high compression is based on missing sample values. The lower 10 bits are essentially wasted as almost every sample is a multiple of 32767 / 32, and since that's not an even power of 2 the algorithms in many lossless compressors that eliminate redundant LSBs don't do anything. I have no guess how this file got like this, but it essentially has only 14 bits of resolution.

A long time ago I considered trying to take advantage of this to get better compression for real CDs. I seem to remember that about 10% of my CD collection showed some statistical discrepancy that could be leveraged for improved compression, in some cases up to 10%! The first problem was the complexity (there were many variations on how the missing sample values were manifested) and the other thing that bothered me was that I would be taking advantage of something that really shouldn't be there at all with well-mastered material. I would be curious as to how common this is in modern recordings, but this definitely strikes me as an edge-case not worth considering beyond mathematical curiosity.
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probedb
post Nov 13 2013, 09:34
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QUOTE (xnor @ Nov 12 2013, 13:14) *
Then why did the developer announce a new alpha release in the coming days? dry.gif

It's still being actively developed, there's just not much to fix especially in the stable version.


You answered your own question, the clue being the word alpha wink.gif I said stable.

Even the latest alpha is dated October 2012. Taking 3 years to get a new release out when it's been in beta is what I'd call not actively developed.
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birdie
post Nov 13 2013, 10:11
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I smell something extremely fishy here.

Like your album has several bit-identical songs, so 7z takes advantage of its enormous dictionary.

Care to share the album name?
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Kees de Visser
post Nov 13 2013, 11:36
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Just to make sure: is the test file in 24 bit 96 kHz format ? The spectrogram shows content up to 48 kHz, indicating a sampling rate of 96 kHz, but the topic mentions 48 kHz.
Also, has it been verified that the process is lossless ?
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Juha
post Nov 13 2013, 12:26
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Probably the test sample wav were recorded using std Audacity, which does let record/save 24-bit wav files bits 17-24 filled with zeros.

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2Bdecided
post Nov 13 2013, 12:32
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bryant's already explained exactly what's happening - why are you guys still speculating?
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