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Test your soundcard for clipping, with this sample
Jan S.
post May 26 2003, 19:57
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For everybody fighting with occasional clipping (or perfectionists wanting to test everything) you should try the attached sample, udial.

Testing:
  • play the sample in your favourite player (decoded or not, having disabled all DSPs and EQs that can interfere)
  • if the output sounds weird at any time you should:
    • lower the output vol. in your soundcard config (should be the speaker icon in your system tray).
    • For some soundcards 48kHz is better (audigy 2 etc.).
    • lower the vol. till the sample doesn't sound weird at any time.
The output will sound really weird if your settings clip.
Your output can occasional clip without you knowing/hearing it. But for us perfectionists this will theoretically give a better quality output.

ATTENTION: Play this sample at a low volume anytime, even if you hear nothing special! It can be very harmful to equipment and/or your ears.
It's strongly recommended to use some very cheap (PC) speakers if you want to test this,
otherwise you might really ruin your tweeters (it has happened several times already).

Attached File(s)
Attached File  udial.zip ( 217.55K ) Number of downloads: 20646
 
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DickD
post Jun 3 2003, 10:23
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[EDIT]This post has some factual assumptions that were incorrect, as pointed out by Garf in the next post. I think I found the root cause in the post after his[/EDIT]

The FB2K database (if enabled) may have needed refreshing, I guess.

When I started typing this post, I suspected the console message is referring to clipping detected from the Resampler output. The tiniest amount of attenuation (volume control -0.5 dB) would be enough to stop this.

The 20 kHz +/- 1 kHz frequency-modulated sine wave in the original is almost full scale (probably a bit less so it can add to the extreme values of the dialling tones and reach full scale but no higher). The sampling points at 44.1 kHz are below full scale (hence the track peak of 0.997...) because they don't happen to coincide with the peaks.

Assuming I'm correct about the target amplitude of the sine waves, a perfect (infinitely long) reconstruction filter when upsampling should generate a track peak of 1.000000 at most on every peak where the sampling point lines up perfectly with the peak of the sinusoid. I'd imagine the Resampler (SSRC) DSP plugin, even in Slow mode (long reconstruction filter window) and 64-bit precision, will still show some very subtle (inaudibly subtle) variation in loudness at frequencies so near to the Nyquist limit (22.049... kHz is the highest frequency that can be accurately represented by 44100 Sa/s sampling). This could cause tiny amounts of clipping, such as 1.00001, which would generate inaudible clipping distortion, even on this sample, yet would be just high enough to trigger the console warning.

(I actually tried resampling to 48000, WAV 64-bit floating point to test this, and found that FB2K's resampler doesn't cause clipping on this sample).

Using Resampler: Slow mode, 64 bit:
Track Gain = +18.210000 dB
Track peak = 0.997059

Fast mode, 64 bit (same for 32 bit):
Track peak = 0.997217

So (without using Preamp or Equalizer) these shouldn't clip on their own.

What about adding dither? Could that cause clipping?

EDIT: No, it can't, as Garf points out below, the ditherer won't add dither if the added noise would push the sample value beyond +1.000 or -1.000.

Assuming you use 16-bit playback (which I'm not sure of), setting dither to "strong ATH noise shaping (recommended)" the stronger high frequency content than "no noise shaping" can add about 31 (out of 32767) to a sample value at the peak - just now and again. That's 0.000946, which still isn't enough to exceed 1.000000 if you apply no replaygain.

However, you're using ReplayGain, so it would like to add 18.21 dB, then realises it can't from the peak value of 0.997131, so it's scaling
to get a peak of 1.000000 instead (a gain of about +0.024955 dB). You then add dither, which can take the peak to 1.000946 at most).

Edit: This is not true. Dither is not added if the sample would exceed 1.000000, so it must already exceed 1.000000. The culprit is identified in my next message.

That is just enough to clip, but it's so incredibly subtle (and probably incredibly infrequent) that it clips, that it no audible clipping distortion is heard. However, you do get the warning from FB2K.

I guess it would be a finishing touch for FB2K's clipping prevention (Replaygain) to have an option to take account of the dither type and bit depth by scaling the peak to just below 1.000000 so that dither can't cause it to exceed 1.000000. We could either enter the margin by hand, or FB2K could have a look-up table for dither type versus peak dither amplitude for each bit depth and sampling rate. This is overkill at normal bit depths, where it's inaudible, but for low bit depths like 8-bit, it would be useful if people used strong ATH noise shaping.

Also, Replaygain on real music (this udial sample is NOT real music!) rarely causes clipping if the target volume is 89.0 dB - it hardly ever has positive Album Gain values, and only occasionally has positive Track Gain values.

EDIT: Please see my next post for the real explanation.

This post has been edited by DickD: Jun 3 2003, 11:42
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Posts in this topic
- Jan S.   Test your soundcard for clipping   May 26 2003, 19:57
- - grbmusic   I'll try it and then I tell about it!...   May 26 2003, 20:03
- - grbmusic   It's a kind of joke??? With foobar is imposibl...   May 26 2003, 20:19
- - atici   I listened to it OK with all my DSP plugins off, i...   May 26 2003, 20:25
- - Jan S.   QUOTE (grbmusic @ May 26 2003 - 09:19 PM)It...   May 26 2003, 20:26
- - Jan S.   QUOTE (atici @ May 26 2003 - 09:25 PM)it soun...   May 26 2003, 20:28
- - grbmusic   QUOTE (Jan S. @ May 26 2003 - 04:26 PM)what y...   May 26 2003, 20:44
- - boojum   I am not sure about the distortion. I do get the ...   May 26 2003, 20:54
- - Pio2001   19.5 kHz ! At full power in headphones, I hea...   May 26 2003, 21:47
- - Thikasabrik   Well... it looks as if it isn't clipping for m...   May 26 2003, 22:44
- - ben   Yeah, I just clipped my ears with the 19.5khz tone...   May 26 2003, 23:08
- - outscape   QUOTE (Pio2001 @ May 26 2003 - 03:47 PM)19.5 ...   May 27 2003, 03:25
- - Rizban76   I suppose my sound card is really screwed up. I ca...   May 27 2003, 04:27
- - fewtch   MonkeysAudio is so annoying. No separate WinAMP p...   May 27 2003, 04:45
- - Mr. Mulder   If you give me an email address I cand send you ...   May 27 2003, 07:29
- - anza   When I have foobars resampler on and set to 48kHz ...   May 27 2003, 07:58
- - LPTB   QUOTE I tried with DirectSound and I got nearly sa...   May 27 2003, 08:08
- - KikeG   Ugh! I hear too annoying ultra-high pitched to...   May 27 2003, 08:13
- - Mac   Ugh, you should put a warning when you post sample...   May 27 2003, 08:30
- - freakngoat   That is the craziest sample ever. How does it work...   May 27 2003, 08:45
- - Halcyon   What a useful sample! My results for Audigy 2...   May 27 2003, 09:29
- - Garf   QUOTE (Halcyon @ May 27 2003 - 10:29 AM)Final...   May 27 2003, 10:23
- - tigre   Great work! I knew before that my onboard VIA ...   May 27 2003, 10:59
- - Rasi   the squirling reminds me of a bird singing.... gue...   May 27 2003, 11:01
- - Gabriel   On this computer I get a birdy sound, depending on...   May 27 2003, 11:25
- - fragtal   Does somebody have .flac version of this sample or...   May 27 2003, 12:42
- - tigre   udial.flac   May 27 2003, 12:49
- - fragtal   QUOTE (tigre @ May 27 2003 - 01:49 PM)udial.f...   May 27 2003, 12:52
- - Halcyon   Garf, Why is this sample theoretical? Can you ela...   May 27 2003, 13:15
- - tigre   QUOTE (Halcyon @ May 27 2003 - 04:15 AM)Why i...   May 27 2003, 14:10
- - LPTB   Ok I did a test at work, with SoundMax integrated ...   May 27 2003, 15:15
- - JEN   Wow, that gave me a headache I can hear clicki...   May 27 2003, 15:16
- - Jan S.   QUOTE (JEN @ May 27 2003 - 04:16 PM)Wow, that...   May 27 2003, 15:42
- - fragtal   I have to pull down the master-volume (of the Crat...   May 27 2003, 16:13
- - JEN   OK, I tried it with resampling and here are the r...   May 27 2003, 16:16
- - ViPER1313   Would anyone be willing to take the sweep.wav samp...   May 27 2003, 16:27
- - Sachankara   Ehh... What are you supposed to hear? It sounds li...   May 27 2003, 17:11
- - grbmusic   Jan S. you should advice that take the test with t...   May 27 2003, 17:20
- - sony666   QUOTE (grbmusic @ May 27 2003 - 05:20 PM)Jan ...   May 27 2003, 17:41
- - LPTB   @grbmusic bummer man, sorry for your speakers... ...   May 27 2003, 18:01
- - JeanLuc   Two chains in my system, both fed by a TerraTec EW...   May 27 2003, 18:25
- - tigre   QUOTE (Sachankara @ May 27 2003 - 08:11 AM)Eh...   May 27 2003, 18:49
- - outscape   QUOTE (grbmusic @ May 27 2003 - 11:20 AM)Jan ...   May 27 2003, 18:52
- - LPTB   @tigre About the sample you provided, I can hear q...   May 27 2003, 18:53
- - tigre   Which one?   May 27 2003, 19:07
- - LPTB   The mpc sample you provided named correct.mpc.   May 27 2003, 19:28
- - Pio2001   QUOTE (fragtal @ May 27 2003 - 06:13 PM)I hea...   May 27 2003, 19:45
- - tigre   QUOTE (LPTB @ May 27 2003 - 10:28 AM)The mpc ...   May 27 2003, 19:52
- - LPTB   QUOTE If it's less than in the .mpc file it co...   May 27 2003, 20:02
- - grbmusic   QUOTE (LPTB @ May 27 2003 - 02:01 PM)I tried ...   May 27 2003, 23:37
- - grbmusic   QUOTE (outscape @ May 27 2003 - 02:52 PM)did ...   May 27 2003, 23:40
- - LoKi128   Well, tested with Winamp and my shitty on-board so...   May 28 2003, 01:15
- - KikeG   I tested again at home with my Audiophile, and hea...   May 28 2003, 09:25
- - Pio2001   THIS is a killer sample QUOTE (KikeG @ Ma...   May 28 2003, 11:59
- - lucpes   M-Audio Delta 410 card... dial tone + very high pi...   May 28 2003, 12:38
- - 2Bdecided   In fact, there isn't a hard cut off limit in h...   May 28 2003, 12:42
- - Moitah   When using Winamp's DirectSound plugin (v2.2.6...   May 28 2003, 14:18
- - JeanLuc   QUOTE (grbmusic @ May 27 2003 - 10:37 PM)QUOT...   May 28 2003, 15:16
- - jues   Soundcard: Delta 410. Christ that hurt - yeah, pu...   May 28 2003, 15:37
- - DickD   I have a Win NT4.0 machine with a 'Pro16V-A Pn...   May 28 2003, 16:28
- - Pio2001   This is a picture of the aliases that can appear w...   May 28 2003, 18:33
- - fragtal   I just downloaded the correct.flac and I'm rea...   May 28 2003, 19:46
- - ViPER1313   Sounds fine to me on my SB-Live value w/ 48khz SSR...   May 28 2003, 20:24
- - atici   QUOTE (lucpes @ May 28 2003 - 06:38 AM)M-Audi...   May 28 2003, 20:39
- - Pio2001   QUOTE (ViPER1313 @ May 28 2003 - 10:24 PM)the...   May 28 2003, 20:50
- - kritip   QUOTE (Pio2001 @ May 28 2003 - 08:50 PM)QUOTE...   May 28 2003, 22:32
- - Stuv   Quite interesting sample this one. All ASIO, Wave ...   May 28 2003, 23:56
- - ViPER1313   QUOTE the sweep is more through and wont hurt your...   May 29 2003, 04:23
- - Halcyon   A quick note about Creative cards and audible arti...   May 29 2003, 09:09
- - KikeG   QUOTE (Pio2001 @ May 28 2003 - 08:50 PM)You s...   May 29 2003, 09:37
- - DickD   QUOTE (kritip @ May 28 2003 - 10:32 PM)I real...   May 29 2003, 13:27
- - mrosscook   I have an SB Live card and Harman-Kardon desktop s...   May 29 2003, 14:57
- - LPTB   KikeG, Halcyon You're both correct this is exa...   May 29 2003, 15:03
- - Pio2001   I remember people saying their SB live was incredi...   May 29 2003, 19:58
- - JonPike   Huh.. interesting. On XP here, can't rememb...   May 30 2003, 02:43
- - grbmusic   QUOTE (JeanLuc @ May 28 2003 - 11:16 AM)Sorry...   May 30 2003, 03:21
- - Halcyon   FYI. All of my test were done under WinXP Pro SP1,...   May 30 2003, 07:51
- - DickD   QUOTE (JonPike @ May 30 2003 - 02:43 AM)Hmmmm...   May 30 2003, 13:31
- - mrosscook   Pio, Since there may be issues with the OS for Cr...   May 30 2003, 14:08
- - lucpes   QUOTE (atici @ May 28 2003 - 07:39 PM)lucpes,...   May 30 2003, 14:18
- - Thikasabrik   Well, having tested more thoroughly at different s...   May 30 2003, 14:26
- - Pio2001   Below 44.1 kHz, if the resampling is done with ant...   May 30 2003, 19:01
- - Dave Hamaker   I extracted the sample to a wav file. I looked at...   May 31 2003, 00:30
- - Pio2001   The spectrum of the clipped sample has subharmonic...   May 31 2003, 01:37
- - Dave Hamaker   QUOTE (Pio2001 @ May 30 2003 - 04:37 PM)The s...   May 31 2003, 02:46
- - Pio2001   Here are the results of two bad processes performe...   May 31 2003, 09:29
- - Halcyon   QUOTE Switching to quality 2 (on a 1-4 scale) remo...   May 31 2003, 11:37
- - indybrett   Using Foobar through a Prodigy 7.1 soundcard. Jus...   May 31 2003, 19:29
- - Dave Hamaker   QUOTE (Pio2001 @ May 31 2003 - 12:29 AM)Here ...   May 31 2003, 21:50
- - JonPike   QUOTE (DickD @ May 30 2003 - 04:31 AM)QUOTE (...   Jun 1 2003, 01:48
- - JonPike   "foobar2000 player v0.666 released Changes: ...   Jun 1 2003, 01:57
- - Differenciam   Ack. My laptop made that sound quite painful.   Jun 1 2003, 02:30
- - Chun-Yu   QUOTE (indybrett @ May 31 2003 - 01:29 PM)Usi...   Jun 1 2003, 02:46
- - Halcyon   QUOTE (Chun-Yu @ Jun 1 2003 - 03:46 AM)Q...   Jun 1 2003, 10:09
- - DickD   QUOTE (JonPike @ Jun 1 2003 - 01:48 AM)OK......   Jun 2 2003, 14:36
- - JonPike   QUOTE (DickD @ Jun 2 2003 - 05:36 AM)The late...   Jun 3 2003, 02:42
- - DickD   This post has some factual assumptions that were i...   Jun 3 2003, 10:23
- - Garf   FB2K ditherer and noiseshaper should never cause c...   Jun 3 2003, 10:32
- - DickD   Thanks for the informative reply, Garf. I'll g...   Jun 3 2003, 11:34
- - Halcyon   I need help. I have tried everything that I can t...   Jun 3 2003, 13:53
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