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Bits is Bits? Right? Check Again. George Blood, Safe Sound Archive Joint Technical Symposium Oslo, Norway Monday, May 3, 2010.

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Presentation on theme: "Bits is Bits? Right? Check Again. George Blood, Safe Sound Archive Joint Technical Symposium Oslo, Norway Monday, May 3, 2010."— Presentation transcript:

1 Bits is Bits? Right? Check Again. George Blood, Safe Sound Archive Joint Technical Symposium Oslo, Norway Monday, May 3, 2010

2 Typical Playback Chain Analog source Analog-to-digital converter Digital Audio Workstation Digital File Physical Carrier of Files

3 Typical Playback Chain Analog source Analog-to-digital converter Digital Audio Workstation Digital File Physical Carrier of Files }

4 From ADC to Digital File ADC Digital Output (AES-3) Cable/patching/switching Digital Audio Workstation: Digital File Computer: CPU/Bus/etc. Driver Software OS/Drivers Storage interface/drivers: FW, USB, SATA, FC, iSCSI Storage Device (HDD) Interface: AES-3 to FW/USB/etc.

5 Disappointments Don’t mention brands Don’t tell you our solution Very pervasive problem content/uploads/2010/01/Digital_Audio_Inter stitial_Errors.pdf

6 Disappointments Planned to announce a software tool to automate this testing….

7 Tested Hardware Lynx AES16 M-Audio (96 and 192) M-Box Metric Halo ULN-2 Nagra V SonicStudio 302 (aka ULN2+DSP)

8 Tested Software Boom Metric Halo Console ProTools LE (Mac) Sonic Solutions HDSP Sonic Studio soundBlade SoundForge WaveLab

9 Tested OS Mac OS9 Mac OS X Windows 98 Windows Home Windows ME

10 Tested Drivers Stock drivers (mostly) –OS stock drivers –Hardware bundled drivers Dedicated Drivers –OS 9 (Sonic Solutions) –OS X (SonicStudio & MH)

11 Tested Storage Fat32 FibreChannel (2Gb, RAID5) FireWire 400 HFS+ (SCSI Ultra160) HFS-extended SATA

12 Not Tested Audacity AudioCube [Bias Peak] iSCSI ProTools HD ProTools LE (PC) Pyramix RME ADC to FireWire

13 Testing Multiple Components Simultaneously A b 1 A b 2 B b 1 B b 2 A a 1 A a 2

14 Finding errors 100% Listen –Inefficient –Unreliable Software verification –Doesn’t certify authenticity –Limited parameter testing –Unreliable

15 Finding Errors Null Test: –2 presumed identical files –Sample-accurate alignment –Invert polarity –Add together If a1=a2, then a1 - a2=0

16 Aligning 2 stereo pairs (1)

17 Aligning 2 stereo pairs (2)

18 Aligning 2 stereo pairs (3)

19 Aligning 2 stereo pairs (4)

20 Aligning 2 stereo pairs (5)

21 Aligning 2 stereo pairs (6)

22 …then invert 1 pair

23 Testing for 2 parameters Time –Number of samples Amplitude –Number of bits

24 Null if mis-aligned by 1 sample

25 Error of 76 samples dropped

26 from: content/uploads/2010/01/Digital_Audio_Interstitial_Errors.pdf

27 Bits vs. samples missing

28 Bits vs. samples missing

29 Null if gain changed

30 What happened? New Hardware –Failure Reviewed set up with engineer –Failure Reviewed old systems –Failure Simplified Test –Finally some passes –Failures continue between identically configured systems

31 Qualifying a Control Round Robin Test –A≠B –B≠C –A=C –…B is wrong

32 Qualifying a Control Assumes only one variable at play –Host –I/O Hardware –Driver –Application …test configuration

33 Hardware in hand SonicStudio –Great editor –Semi-proprietary file types –Non-destructive editing –No support for WAV or BWF output –No AES-31 ADL support Nagra V –Simple –Self-contained –Can’t change variables (other than resolution)

34 Results Null tests passed Every time Always Validates testing procedures

35 Talent Pool Head of QA with physics background 2 experienced audio engineers 2 dealers 2 outside technical engineers

36 Tech “support” Universally appalling Short attention span Don’t understand concepts Always some other link in chain Regional sales reps care more Engineer curious but unable to help

37 Computer code “traps” Intractable problem buried in code Build routine to watch for it Applies fix Efficient solution

38 Computer code “traps” Masking (aka “hiding”) problem! –Little crossfades at glitches –Other lies…

39 True Nulls

40 Very small error in Null

41 Close up

42 Incomplete Null

43 Non-zero offset

44 Calculating size of error “Normalize” difference signal –Increases gain to zero headroom 1 bit = ~ 6dB Normalizing amplitude divided by 6dB equals # of bits (amplitude) of difference…

45 Calculating size of error 90dB / 6 dB = 15 bits

46 Incomplete Null Spectrum of difference signal

47 Conclusion Not passing 24 bits Truncating at 16 bits Dithering 16th - 24th bits –More noise but Lower distortion than truncating at 16 bits and dithering 17-24

48 Struggling to keep up Different bit depth, all non-zero Example 3 drops samples

49 Struggling to keep up Example 1 & 2 Normalized -- “properly” dithered

50 “Well-dithered lie”

51 Toggling single bit

52 Are there no limits? “Fatter” difference on L Display higher resolution on R

53 Are there no limits? “Fatter” difference on L “Full” null - absurd gain change - on R

54 Are there no limits? Different residual on L!

55 More absurdities Same hardware, different ages, different results Same configuration, different results on different days Same hardware, good results with one software; poor results with different software

56 Conclusions Get what you pay for –More expensive hardware & software performs better in Null tests Stock drivers aren’t as good as hardware specific drivers –keep up to date, especially after OS upgrades Non-host-based systems perform significantly better Mac-based systems performed better than PC-based systems, but are far from flawless Worst PC and Worst Mac systems equally bad These problems are widely known by manufacturers and blatantly hidden


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