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When I am browsing HSK test files (level 6) here (http://www.chinesetest.cn/godownload.do), I found that the decompressed mp3 and wmv is actually larger than the rar file. I'm very surprised since rar is lossless and mp3/wmv is lossy and lossy usually compresses better than lossless. Why might this happen?
Output of unrar -lt:
UNRAR 5.71 freeware Copyright (c) 1993-2019 Alexander Roshal
Archive: /private/var/root/Desktop/level-6.rar
Details: RAR 4
Name: level-6.wma
Type: File
Size: 26237479
Packed size: 17275823
Ratio: 65%
mtime: 2010-03-18 15:35:19,000000000
Attributes: ..A....
CRC32: 950CFA63
Host OS: Windows
Compression: RAR 3.0(v29) -m3 -md=4M
UNRAR 5.71 freeware Copyright (c) 1993-2019 Alexander Roshal
Archive: /private/var/root/Desktop/HSK/H61001.rar
Details: RAR 4
Name: H61001.mp3
Type: File
Size: 86448468
Packed size: 40408917
Ratio: 46%
mtime: 2011-02-18 10:40:02,000000000
Attributes: ..A....
CRC32: 7C1319AB
Host OS: Windows
Compression: RAR 3.0(v29) -m3 -md=4M
Output of ffprobe:
Input #0, mp3, from '/private/var/root/Desktop/HSK/H61001.mp3':
Metadata:
album : δ֪³ªÆ¬¼¯ (2010-9-13 8:32:01)
title : ÇúÄ¿ 1
track : 1
genre : δ֪
artist : δ֪ÒÕÊõ¼Ò
TLEN : 2162986
id3v2_priv.AverageLevel: \x0b\x04\x00\x00
id3v2_priv.PeakValue: \x1a9\x00\x00
Duration: 00:36:01.11, start: 0.000000, bitrate: 320 kb/s
Stream #0:0: Audio: mp3, 44100 Hz, stereo, fltp, 320 kb/s
Input #0, asf, from '/private/var/root/Desktop/HSK/level-6.wma':
Metadata:
WMFSDKNeeded : 0.0.0.0000
DeviceConformanceTemplate: L1
WM/WMADRCPeakReference: 19841
WM/WMADRCAverageReference: 1995
WMFSDKVersion : 9.00.00.4506
IsVBR : 0
Duration: 00:36:10.67, start: 0.000000, bitrate: 96 kb/s
Stream #0:0(chi): Audio: wmav2 (a[1][0][0] / 0x0161), 44100 Hz, 2 channels, fltp, 96 kb/s
ll (ls -G -lh)
total 630704
-rw-r--r--@ 1 root staff 82M 2 18 2011 H61001.mp3
-rw-r--r--@ 1 root staff 700K 2 7 16:15 H61001.pdf
-rw-r--r--@ 1 root staff 39M 2 7 16:23 H61001.rar
-rw-r--r--@ 1 root staff 729K 2 7 16:19 HSK-2012.xls
-rw-r--r--@ 1 root staff 113M 2 7 16:20 HSK6.7z
-rw-r--r--@ 1 root staff 1.2M 2 7 16:19 HSK6.pdf
-rw-r--r--@ 1 root staff 16M 2 7 16:23 level-6.rar
-rw-r--r--@ 1 root staff 25M 3 18 2010 level-6.wma
drwxr-xr-x@ 7 root staff 224B 3 25 2016 六级录音
Download link:
http://www.chinesetest.cn/userfiles/file/dagang/level-6.rar
http://www.chinesetest.cn/userfiles/file/HSK/level6/H61001.rar
One guess, mp3 is a compression algorithm that is based on fragments of time, with only a small amount of back- and forward-looking in order to keep the decompressor memory and CPU requirements low. Sections of repeated audio (or silence) are likely to result in similar blocks of output being repeated and therefore result in improved subsequent compression by other compressors. You do not decode the entire mp3 to play it as that would result in a need to store up to 40MB for about 3 minutes, fine for high-end devices, but impossible for low end microcontrollers. – Mokubai – 2020-02-07T10:53:33.053