Le Numérique Est-il Fidèle ?, Illusion ou réalité ? |
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Sat 2 Sep 2006, 09:40
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La madame est partie.
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super article, j'ai fait un petit digest des passages les plus parlants :
The loudness war, as we shall see, has now become so furious that equipment downstream of mastering is not able to pass or reproduce the audio material without adding signicant distortion to it. It appears to be a contradiction that the professional audio industry promotes better standards such as 96 kHz sampling, 24 bit resolution, DSD, exotic dither schemes etc. and the hi- world is becoming conscious about jitter-rejection etc. – while the current main delivery format, 16 bit/44.1 kHz, is becoming more and more abused. Most pop releases now get so much distortion added during reproduction that 16 bit resolution is completely overkill.
The distortion problems arise because of more or less conscious use of clipping in the digital domain during production and mastering. Digital processors may have familiar names like "Limiter" or "Compressor", but there is no guarantee they will have much in common with their analog counterparts, and not even that they obey the fundamental sampling criteria. Clipping can also be hidden inside computer processors, DAWs or digital mixers, making later recovery difcult or in many cases impossible.
While frequent clipping in the digital domain can cause listening fatigue, things are made worse during mastering when clipped material is normalized to digital full scale. Such material will later be subject to additional distortion during data-reduction, sample rate conversion and digital to analog conversion.
Both narrow-band and broadband (e.g. clipped) signals can have a theoretical peak value larger than the actual representation in the digital format. The simplest example is a high frequency sine wave. Depending on frequency and phase the peak value of the digital sine wave representation may be up to 3 dB lower than the theoretical, or analog, peak value. If this headroom is used for increasing the digital gain, the peak value of the reconstructed analog signal will be higher than the DC value representing digital full scale, 0 dBFS.
One way of avoiding the problem of clipping is to reduce the overall peak level of the recordings. As this also reduces the average level it will probably be considered unacceptable by many sound producing professionals, so another solution is called for. An alternative is to to reduce the digital level in the playback environment prior to digital to analog conversion. This would reduce distortion only in future products, however, leaving hundreds of millions of playback devices with potential problems. The price for this constructional measure is a reduced signal-to-noise ratio in the D-to-A conversion circuit.
Using an inter-sample precision digital limiter with the threshold value set to -0.3 dBFS, that is, basically just to reduce overshoots, the distortion of the DACs disappeared almost completely. The overall loudness of the signal was not reduced, however, so for many applications this seems to be the better option.
In conclusion, we have demonstrated that the problem of overload in digital to analog conversion, sample rate conversion and in connection with data-reduction systems is denitely present in practice. Measuring and listening to in vivo signals provide a strong evidence that headroom in the digital production chain has been exhausted, and that audio quality currently may be limited for this reason rather than a basic lack of resolution or a high enough sample rate.
Because the audio industry is currently stuck with non-intelligent level restrictions, such as counting consecutive samples at full scale, mastering engineers should start using oversampled meters and limiters, or at least normalize against e.g. -2 or -3 dBFS rather than 0 dBFS. It should also be noted that some data reduction codecs are even more sensitive to excessively hot level than a linear signalpath.
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La Miss est partie sur Second Life et se prélasse sur du sable fin, entourée de créatures de rêves dans une végétation luxuriante... enfin une retraite bien méritée !!!
Yodelhihoo. ;-)
NB : ne laissez pas de messages dans ma bal, je n'y suis plus...
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Sun 3 Sep 2006, 12:17
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Très intéressante, cette discussion QUOTE (Miss Kiki @ sam 2 sep 2006, 09:40) ![*](style_images/en/post_snapback.gif) (...) Digital processors may have familiar names like "Limiter" or "Compressor", but there is no guarantee they will have much in common with their analog counterparts (...) Ca, ça ne m'étonne pas. Pour avoir le "compresseur" numérique, il faut modéliser le comportement de celui analogique sinon on ne peut pas faire les calculs. Et dans toute modélisation, il y a des hypothèses (il peut s'agir de théories +/- démontrées, de choix du concepteurs etc.). Autrement dit le fait de modéliser revient à regarder la réalité sous un angle particulier. De ce fait, le plug in - qui résulte de cette modélisation et du développement qui s'ensuivent - est tributaire de l'angle sous lequel on a regardé la réalité. Après, on peut s'amuser à faire des calculs ... mais moi, j'aime bien les paraboles
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Con*eries inside
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Posts in this topic
wfplb Le Numérique Est-il Fidèle ? Sat 2 Sep 2006, 00:51 Miss Kiki le pdf sur l'overload ici Sat 2 Sep 2006, 08:57 Mr.T Très intéressant cet article effectivement.
C... Sat 2 Sep 2006, 10:12 Miss Kiki T pour que ce soit efficace il faut baisser un peu... Sat 2 Sep 2006, 10:19 blek Ah oui, c'est vraiment très interressant. Merc... Sat 2 Sep 2006, 10:33 Mr.T Oui nan mais quand même la Miss, ja sais un peu ça... Sat 2 Sep 2006, 10:41 Miss Kiki QUOTE (wfplb @ sam 2 sep 2006, 01:51) Fin... Sat 2 Sep 2006, 16:30 Messensib Merci William d'avoir ouvert ce sujet à la sui... Sat 2 Sep 2006, 16:45![|](style_images/en/to_down_pipe.gif) wfplb QUOTE (Messensib @ sam 2 sep 2006, 17:45)... Sun 3 Sep 2006, 01:45![|](style_images/en/to_down_pipe.gif) ![](style_images/en/spacer.gif) Mr.T QUOTE (wfplb @ dim 3 sep 2006, 02:45) - P... Sun 3 Sep 2006, 11:12![|](style_images/en/to_down_pipe.gif) ![](style_images/en/spacer.gif) ![|](style_images/en/to_down_pipe.gif) Miss Kiki QUOTE (Mr.T @ dim 3 sep 2006, 12:12) QUOT... Sun 3 Sep 2006, 12:31![|](style_images/en/to_down_pipe.gif) ![](style_images/en/spacer.gif) ![|](style_images/en/to_down_pipe.gif) ![|](style_images/en/to_down_pipe.gif) melenko QUOTE (Miss Kiki @ dim 3 sep 2006, 13:31)... Sun 3 Sep 2006, 19:52![|](style_images/en/to_down_pipe.gif) ![](style_images/en/spacer.gif) ![|](style_images/en/to_down_pipe.gif) ![|](style_images/en/to_down_pipe.gif) gasy QUOTE (Miss Kiki @ dim 3 sep 2006, 12:31)... Mon 4 Sep 2006, 09:49![|](style_images/en/to_down_pipe.gif) ![](style_images/en/spacer.gif) ![|](style_images/en/to_down_pipe.gif) wfplb QUOTE (Mr.T @ dim 3 sep 2006, 12:12) ... ... Sun 3 Sep 2006, 12:35![|](style_images/en/to_down_pipe.gif) ![](style_images/en/spacer.gif) Messensib QUOTE (wfplb @ dim 3 sep 2006, 02:45) QUO... Mon 4 Sep 2006, 15:12 julbul QUOTE Mais je commence petit.....
ha! et ç... Sat 2 Sep 2006, 20:32![|](style_images/en/to_down_pipe.gif) Pame QUOTE (julbul @ sam 2 sep 2006, 19:32) QU... Sun 3 Sep 2006, 00:50![|](style_images/en/to_down_pipe.gif) ![](style_images/en/spacer.gif) Pame QUOTE (Pame @ sam 2 sep 2006, 23:50) QUOT... Wed 6 Sep 2006, 01:12![|](style_images/en/to_down_pipe.gif) ![](style_images/en/spacer.gif) ![](style_images/en/spacer.gif) Miss Kiki QUOTE (Pame @ mer 6 sep 2006, 02:12) J... Wed 6 Sep 2006, 11:03![|](style_images/en/to_down_pipe.gif) ![](style_images/en/spacer.gif) ![](style_images/en/spacer.gif) ![](style_images/en/spacer.gif) gasy Si on pose cette hypothèse : pas de fidélité au ni... Wed 6 Sep 2006, 12:52 Miss Kiki A propos, et quid des convertos du style sygma-del... Sun 3 Sep 2006, 14:14 Messensib Sniff !!!! je suis un incompris. C... Mon 4 Sep 2006, 09:44 julbul QUOTE Pour rester au ras des pâquerettes (comme il... Mon 4 Sep 2006, 16:06 Messensib Je viens de relire mon premier post (page 1) et je... Tue 5 Sep 2006, 20:39![|](style_images/en/to_down_pipe.gif) olafnoise QUOTE (Messensib @ mar 5 sep 2006, 21:39)... Tue 5 Sep 2006, 21:36![|](style_images/en/to_down_pipe.gif) wfplb QUOTE (Messensib @ mar 5 sep 2006, 21:39)... Tue 5 Sep 2006, 23:03 Miss Kiki Avant de parler chiffons je voulais proposer une c... Tue 5 Sep 2006, 20:53![|](style_images/en/to_down_pipe.gif) Messensib QUOTE (Miss Kiki @ mar 5 sep 2006, 21:53)... Tue 5 Sep 2006, 21:23![|](style_images/en/to_down_pipe.gif) ![](style_images/en/spacer.gif) Miss Kiki QUOTE (Messensib @ mar 5 sep 2006, 22:23)... Tue 5 Sep 2006, 22:37 Miss Kiki tu fais le filou ... ;-)
Voilà l'extrait que ... Wed 6 Sep 2006, 00:16 Messensib Si on parle de Gödel,et de ses théorèmes ( vers 19... Wed 6 Sep 2006, 10:58![|](style_images/en/to_down_pipe.gif) wfplb QUOTE (Messensib @ mer 6 sep 2006, 11:58)... Wed 6 Sep 2006, 23:05 gasy Le numérique est-il fidèle ? Quand je relis cette ... Wed 6 Sep 2006, 10:59 Miss Kiki L'erreur est dans la façon de dire les choses ... Wed 6 Sep 2006, 13:08![|](style_images/en/to_down_pipe.gif) gasy QUOTE (Miss Kiki @ mer 6 sep 2006, 13:08)... Wed 6 Sep 2006, 13:17 karlos Finalement tout ceci résonne avec la caverne de So... Wed 6 Sep 2006, 13:38 Miss Kiki je comprend pas ou tu veux en venir ...
l'ore... Wed 6 Sep 2006, 23:27![|](style_images/en/to_down_pipe.gif) wfplb QUOTE (Miss Kiki @ jeu 7 sep 2006, 00:27)... Thu 7 Sep 2006, 00:24![|](style_images/en/to_down_pipe.gif) ![|](style_images/en/to_down_pipe.gif) Miss Kiki QUOTE (wfplb @ jeu 7 sep 2006, 01:24) L... Thu 7 Sep 2006, 11:32![|](style_images/en/to_down_pipe.gif) ![|](style_images/en/to_down_pipe.gif) ![](style_images/en/spacer.gif) LaPanthereRose QUOTE (Miss Kiki @ jeu 7 sep 2006, 11:32)... Mon 18 Dec 2006, 01:57![|](style_images/en/to_down_pipe.gif) Messensib QUOTE (Miss Kiki @ jeu 7 sep 2006, 00:27)... Thu 7 Sep 2006, 12:02 gasy QUOTE (wfplb @ mer 6 sep 2006, 23:05) .. ... Thu 7 Sep 2006, 10:36 karlos QUOTE Je déteste Platon qui pense que la "réa... Thu 7 Sep 2006, 12:53 Messensib Pardon à gasy et à miss kiki de ne pas avoir lu le... Thu 7 Sep 2006, 15:32![|](style_images/en/to_down_pipe.gif) Miss Kiki QUOTE (Messensib @ jeu 7 sep 2006, 16:32)... Thu 7 Sep 2006, 15:40![|](style_images/en/to_down_pipe.gif) ![](style_images/en/spacer.gif) abdul6 QUOTE (Miss Kiki @ jeu 7 sep 2006, 16:40)... Thu 7 Sep 2006, 16:12 gasy QUOTE (Messensib @ jeu 7 sep 2006, 12:02)... Thu 7 Sep 2006, 16:22![|](style_images/en/to_down_pipe.gif) abdul6 QUOTE (gasy @ jeu 7 sep 2006, 17:22) QUOT... Thu 7 Sep 2006, 16:36 julbul QUOTE Finalement tout ceci résonne avec la caverne... Thu 7 Sep 2006, 20:15![|](style_images/en/to_down_pipe.gif) wfplb QUOTE (julbul @ jeu 7 sep 2006, 21:15) On... Fri 8 Sep 2006, 08:31![|](style_images/en/to_down_pipe.gif) ![](style_images/en/spacer.gif) Messensib QUOTE (wfplb @ ven 8 sep 2006, 09:31) QUO... Fri 8 Sep 2006, 14:49![|](style_images/en/to_down_pipe.gif) ![](style_images/en/spacer.gif) ![](style_images/en/spacer.gif) wfplb QUOTE (Messensib @ ven 8 sep 2006, 15:49)... Fri 8 Sep 2006, 23:27![|](style_images/en/to_down_pipe.gif) ![](style_images/en/spacer.gif) ![](style_images/en/spacer.gif) ![](style_images/en/spacer.gif) Messensib QUOTE (wfplb @ sam 9 sep 2006, 00:27) QUO... Sat 9 Sep 2006, 10:54![|](style_images/en/to_down_pipe.gif) ![](style_images/en/spacer.gif) ![](style_images/en/spacer.gif) ![](style_images/en/spacer.gif) LaPanthereRose QUOTE (wfplb @ ven 8 sep 2006, 23:27) QUO... Mon 18 Dec 2006, 02:43![|](style_images/en/to_down_pipe.gif) ![](style_images/en/spacer.gif) ![](style_images/en/spacer.gif) ![](style_images/en/spacer.gif) ![](style_images/en/spacer.gif) LaPanthereRose (PS : il y avait aussi le problème de limiter à ce... Wed 20 Dec 2006, 08:23 blek "Tout n'est qu'illusion !" Ç... Thu 7 Sep 2006, 20:44 Miss Kiki Appelle Lassie ... !!! ... ... Thu 7 Sep 2006, 21:05 gasy QUOTE (abdul6 @ jeu 7 sep 2006, 16:36) ce... Fri 8 Sep 2006, 10:27 karlos QUOTE (wfplb @ ven 8 sep 2006, 07:31) Pou... Fri 8 Sep 2006, 15:22![|](style_images/en/to_down_pipe.gif) gasy QUOTE (karlos @ ven 8 sep 2006, 15:22) De... Fri 8 Sep 2006, 16:19 Messensib Si je poste aujourd'hui ici, ce n'est pas ... Fri 8 Dec 2006, 18:03![|](style_images/en/to_down_pipe.gif) wfplb QUOTE (Messensib @ ven 8 déc 2006, 18:03)... Sun 10 Dec 2006, 02:51 Blue velvet La bataille des deux druides ! Mon 11 Dec 2006, 22:48 Messensib Je viens de relire TOUT ce sujet. D'abord, je ... Wed 20 Dec 2006, 09:54
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