Old 27th February 2007, 05:24   #1
Jerethi
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Possible issue with in_vorbis

Okay, first the preliminaries: I'm using Winamp 5.33, on a clean install, without any third-party plugins. I'm using the latest sound drivers available for my sound card, on a Windows XP SP2 Professional system.

I've detected an odd playback issue with one of my Ogg Vorbis files. At one point during playback, the sound becomes very distorted (sounds much like static). So far, I've only identified this problem with one audio file, but it nonetheless appears to be a problem. I've additionally verified that this problem also occurs on my laptop, using Winamp 5.33. I played the same file with a different media player (Foobar2000) and did not hear any playback issues, and I also played the file on a DAP and again did not notice any issues. I also decoded the Vorbis file to wave, and played that file to verify it wasn't just artifacts in the encoded file, and I did not hear any issues in the wave file either. The Vorbis file was encoded using Lancer-enhanced aoTuV R1.

And the grand finale: I've uploaded a section of the file where playback gets distorted to my webserver for testing purposes. The file is available at www.assortmentstoday.com/music/sample.ogg. You'll notice that if you decode it to wave and play it in Winamp, there are no playback issues.

I'd appreciate any feedback on whether this is a valid issue with vorbis playback in Winamp!
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Old 1st March 2007, 20:26   #2
DJ Egg
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Try unchecking "Use dither" in Winamp > Prefs > Playback.
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Old 2nd March 2007, 02:51   #3
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Ah, that worked perfectly! Thanks for the help on this one, DJ Egg, and my apologies for not recognizing this as a user preference as opposed to a bug in Winamp.
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Old 2nd March 2007, 07:40   #4
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Well, it's actually just a badly encoded file to blame, as far as I can tell.

It also distorts in foobar when enabling dither in Prefs > Output.

Possibly something to do with the beta encoder you used:

Vendor: BS; Lancer(SSE2) [20061013] (based on aoTuV r1 [20051117])

Maybe try an aoTuV 4.51b5 based encoder instead (there's one included in the latest Winamp Essentials pack)
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Old 2nd March 2007, 08:16   #5
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Here's some follow up:

I encoded a file with Oggenc2.83 using aoTuVr1 (MSVC6 compiled), which is the Hydrogenaudio-recommended encoder, and still heard the same results with dither enabled Winamp. Note that aoTuVr1 is a rebranded aoTuV beta 4.51 encoder, according to the HA wiki (link).

I encoded a second file with Oggenc2.83 using libVorbis v1.1.2 (also MSVC6 compiled), and again heard the same results with dither enabled.

In both instances, I encoded the files via command line in Windows XP with Oggenc2.exe.

These results suggest that the issue is not related to the encoder used. I thought that perhaps the additional tunings after aoTuV b2 might be causing the problems, but the issue even appears in files encoded with libVorbis libraries. I suspect this issue will need further investigation.
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Old 8th March 2007, 04:41   #6
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Hrm... does the "Use dither" option affect WAV playback? Most WAVs are already dither, so perhaps it does not. Jerethi, try transcoding the Vorbis sample to MP3 to see if the problem persists in another lossy codec?



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Old 8th March 2007, 10:28   #7
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FYI, Dither is currently used for ogg vorbis and flac only.

Note that the same distortion can be heard when enabling dither in foobar2k
(fb2k > prefs > output: 16-bit + dither)
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Old 8th March 2007, 23:36   #8
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Ah, I had assumed that the dithering was a global playback option like the rest of what's in the Playback prefs branch.

I know this would require additional coding, but it might be wise, if dither is enabled, to automatically scale the source down by the peak amplitude of the dithering such that this clipping does not occur.

Or perhaps just remove the dither option entirely, since it has so much more potential to introduce quite audible artifacts as opposed to any very-subtle dynamic range benefits.



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Old 10th March 2007, 23:42   #9
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For what it's worth, on the latest version of fb2k, with 16-bit output and dither enabled, I am unable to hear the same distortion (or, if it is there, certainly not to the same extent that I'm able to hear it in Winamp 5.33).
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