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MP3 decoding differences, foobar2000 1.2 beta 1
Arite
post Dec 17 2012, 20:54
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Member No.: 43904



foobar2000 v1.2 has switched to using FFmpeg for decoding MP3s (and other codecs). I believe before (v1.1.18 and earlier) it used mpg123 for decoding.

I thought I'd compare the decoded WAV files from an MP3 file (AFAIK FhG encoder) created using v1.1.18 and v1.2 beta 1, respectively.

foobar2000 v1.1.18:
CODE
Track converted successfully.
Total encoding time: 0:06.396, 16.88x realtime

foobar2000 v1.2 beta 1:
CODE
Track converted successfully.
Total encoding time: 0:00.593, 182.08x realtime

That's quite a notable speed change smile.gif (next test was only 2x as fast though).

However doing a bit compare yields:
CODE
Differences found: 14232 sample(s), starting at 1.1842404 second(s), peak: 0.0000305 at 1.1842404 second(s), 2ch

Is this normal/to be expected? My understanding is that mpg123 is the/one of the most accurate decoders.

I tried it on another file (LAME 3.98r -V 0 encoded) and that also failed the bit compare test. Decoding speeds:
CODE
v1.1.18:
Track converted successfully.
Total encoding time: 0:02.964, 112.78x realtime

v1.2 beta 1:
Track converted successfully.
Total encoding time: 0:01.435, 232.96x realtime

^So about 2x as fast - could be due to FFmpeg being multi threaded.

Bit comparing:
CODE
Differences found: 76491 sample(s), starting at 0.5605442 second(s), peak: 0.0000305 at 0.5605442 second(s), 2ch

My question is why is FFmpeg's MP3 decoding different, and is it more or less accurate than mpg123?

Cheers, Arite.

This post has been edited by Arite: Dec 17 2012, 20:55
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lvqcl
post Dec 18 2012, 15:58
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Posts: 3328
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MP3 decoding speed via foo_benchmark. Test file: 221kbps (LAME 3.97 -V2, stereo, 44.1k). Test CPU: Intel Core2, SSE up tp 4.1.

1.1.18: 210x realtime; 1.2 b1: 463x realtime.
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Posts in this topic
- Arite   MP3 decoding differences   Dec 17 2012, 20:54
- - Andreasvb   Not sure, but it's the decoder that's chan...   Dec 17 2012, 22:43
|- - Arite   QUOTE (Andreasvb @ Dec 17 2012, 21:43) No...   Dec 17 2012, 23:48
- - mezenga   QUOTE (Arite @ Dec 17 2012, 11:54) My que...   Dec 17 2012, 23:50
- - Andreasvb   Don't know why you would decompress an MP3 to ...   Dec 18 2012, 01:08
- - kode54   At 16 bit integer precision, the peak difference y...   Dec 18 2012, 02:25
- - Arite   Thanks - I re-did the comparison at 32-bit; the re...   Dec 18 2012, 02:43
|- - Garf   QUOTE (Arite @ Dec 18 2012, 02:43) I...   Dec 18 2012, 09:21
- - nu774   Looks like channel mapping of 6.1ch AAC is incorre...   Dec 18 2012, 04:13
|- - Peter   QUOTE (nu774 @ Dec 18 2012, 04:13) Looks ...   Dec 18 2012, 13:15
- - Garf   By the way, when decoding to disk your disk is goi...   Dec 18 2012, 09:26
- - lvqcl   MP3 decoding speed via foo_benchmark. Test file: 2...   Dec 18 2012, 15:58
- - nu774   Thanks for quick fix. In my environment (Core i5 m...   Dec 18 2012, 16:10
- - Arite   QUOTE (Garf @ Dec 18 2012, 08:21) QUOTE (...   Dec 18 2012, 19:49
- - PHOYO   FFmpeg can decode TAK so why not support it out of...   Dec 18 2012, 23:44
|- - mezenga   QUOTE (PHOYO @ Dec 18 2012, 15:44) FFmpeg...   Dec 19 2012, 03:40
- - IgorC   Atom N2600. LC-AAC ~128 kbps single thread mode...   Dec 19 2012, 00:30
- - Heliologue   While I understand why 1.2 may choose to not use f...   Dec 22 2012, 04:58
|- - Garf   QUOTE (Heliologue @ Dec 22 2012, 04:58) W...   Dec 23 2012, 11:06
- - Porcus   QUOTE (Arite @ Dec 17 2012, 20:54) My que...   Dec 22 2012, 13:03
- - lvqcl   BTW fb2k 1.2b2 decodes SBR part of HE-AAC files di...   Dec 22 2012, 15:07


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