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Quirino's corner
by
Quirino Cieri

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"Pure Audio"  BluRay discs: Something is (slowly) moving
 

I think very few of us have heard of BluRay discs that contain only high-resolution audio tracks without video, adopting the protocol "Pure Audio"... and fewer still have them in their own record collection.
Yet, in my opinion, this is a real missed opportunity for our audio world. The Pure Audio protocol (which is not a new format, but only a way to manage audio streams within a BluRay disc, which is then read by any BD player) was presented in 2009 and standardized by AES in the following year. To summarize, the benefit of the protocol "Pure Audio" is to control the reading of a BluRay disc as if it were a normal CD, simply by inserting the disc into the player; playback starts automatically, without having to select the appropriate item from the main menu and without ever needing to turn on the TV.
At that point, track skips or fast forward / rewind will be carried through the usual buttons on the remote control and you also can switch in real time between the various formats on the disk (eg. PCM stereo, multichannel PCM, DTS-HD Master Audio, etc.) using the four colored buttons found on all the remote controls of BluRay players. So I consider a very pleasant and interesting news the presentation of a new edition in Pure Audio recently published by Decca, "The Ring of the Nibelung" by Wagner conducted by
Sir Georg Solti, to celebrate what would have been his 100th birthday (Solti was born in 1912 and died in 1997). The original master tapes were acquired digitally in stereo PCM at 192 kHz / 24 bit. In this case, the laboratories' msm-studios ", which carried out the BluRay authoring, assigned the four colored buttons on the remote control to navigate through the four operas that comprise the Ring (instead to use them to select the different audio streams) without the necessity to switch-on the TV screen. However the BluRay is just one of the media contained in this edition, really rich, which includes 14 CDs with The Ring of the Nibelung, 2 CDs with an introduction to the Ring by a pupil of Wagner (Deryck Cooke), 1 DVD with a BBC/ORF documentary ("The Golden Ring") in English and German, 1 CD with the Overtures by Wagner recorded in Vienna during the years of the Ring, and finally the BluRay which has been mentioned, as well as libretti, scores, more descriptive material etc.
The cost of the entire box should be about 250 Euro.

This is the official link posted by Pure Audio BluRay on Facebook (you do not need to be registered to read it):
http://www.facebook.com/notes/pure-audio-blu-ray/soltis-historic-der-ring-des-nibelungen-released-on-pure-audio-blu-ray-by-decca-/527237273969749

This other French link includes also a beautiful promotional video where you can hear the quality of the remastering done (of course... in a small scale, but the result is very good already):
http://www.hdfever.fr/2012/09/19/sir-georg-solti-the-ring-coffret-deluxe-17-cd-pure-audio-blu-ray/

And for those who want to further investigate the issue, I conclude with a description of the characteristics of Pure Audio with some comments on its purpose and its potential. First, the "Pure Audio Blu-ray" is a method, not a new format, designed to produce an audio-only Blu-Ray disc and allow its use in the easiest way possible, while maintaining compatibility with all existing and future Blu-ray players.
This project was proposed to AES by Stefan Bock of Msm-studios of Monaco (Germany) and the path to the
standard began August 10, 2009. The final approval of the project and its transformation into an AES standard, with the number X-188, took place May 22, 2010.
The specific name of the standard is: “AES-X188, Screen-less navigation for high-resolution audio on Blu-ray Discs”.
Its purpose: “To recommend a method for authoring an audio-only Blu-ray Disc to enable playback in screen-less consumer systems, and to provide simple stream and track selection using the remote control of a normal Blu-ray Disc player.”
Its target: “Record companies who wish to offer a high-resolution product using current technology; mastering facilities, and recording studios; end users who wish to enjoy high-resolution audio.”
For the official link: http://www.aes.org/standards/meetings/init-projects/aes-x188-init.cfm

It is also possible to insert a further function in the disc (also developed by Msm-studios) called "mShuttle", which allows you to input data and additional files (eg MP3 or FLAC files) on the disc and listen them via PC, connected to Blu-ray via home network.The Pure Audio Blu-ray project started from the consideration that the audio world had been in a sense "orphan" of a high-resolution format accepted by the market, where production costs are sustainable, widespread, cheap for customers and easily availabile.The previous SACD and DVD-Audio formats, despite their undoubted intrinsic validity, are unfortunately never become mass spread. The SACD is now confined to a niche market, with continuous trend to extinction; the DVD-Audio is considered dead. In addition to read SACD and DVD-Audio a special multi-player is requested: this limitation has always prevented a wide spread of both formats, besides the fact that very often the public has seen the existence of both the media as yet another " format war". The Blu-ray format instead has had a continuous growth and spread worldwide. In the U.S. it was present at the end of 2011 in the homes of 40 million Americans, for a penetration rate of 38%
(source: http://www.degonline.org/pressreleases/2012/DEG_year_end_2011.pdf).

Although the Blu-Ray was not born specifically for audio, as it has been conceived by the Hollywood studio majors to distribute the film and not by organizations such as AES or by companies in the audio industry (such as Philips and Sony , when they allied to create and to make approve the CD-Audio), there is no doubt that its features for the basic stereo format (Linear PCM at 192 kHz - 24-bit) allow for superlative audio quality, much higher than CD-Audio quality (44.1 kHz - 16 bit), higher than DVD-Video quality (96 kHz - 24 bit) and directly comparable to quality of SACD and DVD-Audio (192 kHz - 24 bit). Moreover, the maximum sample (Linear PCM 192/24) can also be applied to audio multichannel with quality characteristics identical for each channel, which is not possible with the previous formats. From all this it was clear that the audio world could not ignore the Blu-ray format, relegating it to a mere complement to the video: it was only to determine the best way to use it according to the modalities, expectations and specific target our industry. So the Pure Audio Blu-ray joins also the world of high-definition music to be downloaded online from the various dedicated websites, meeting all those people who for various reasons:
- They do not have a PC and do not want it (either by choice or due to lack of skills);
- Despite having a PC, they do not know how to use it at best and therefore can not easily manage the high-definition music files (how to download, how to storage, which programs to use for reading, how to make secure backup of downloaded data, how to install interfaces and their drivers, how to connect physically the PC to the interface and then the interface to the stereo system, and so on).
- Despite having a PC and knowing ho to use it, they don’t have a high-speed Internet connection;
- Despite having all the necessary and also a high-speed connection, they get annoyed with the long time required for the transfer of a high-resolution full disc (and consider not always convenient the costs to do it);
- Even if all the above point are overcome, they know that people at their home (wife, children, elders...) can feel themselves uncomfortable and "limited "in their use of new technologies (expecially the elderly);
- Finally: while being comfortable with all of the above, they continue to feel a sense of nostalgia for the "physical media" (cover, booklet, disc): that is, something that has always built step by step their music collection.
Now majors can offer to their public the same opera on traditional disc, with the simultaneous presence of high-resolution multiple audio tracks on the same disc, selectable and comparable each other simply by pressing the colored buttons on the remote control. Also the cost is not a problem, because the same authoring system used for a Blu-ray (now present in many studios) can be used to create a Pure Audio Blu-Ray, at no further cost. From this it follows that the phenomenon of piracy too can be reduced: when a user may purchase a Pure Audio Blu-ray disc with the quality we have said, plus the book, with a sense of "real ownership" of the opera and all at a price like any other blu-ray disc, why to download only the tracks from pirate sites? Since the beginning of the definition of the standard, Denon published a special disc from the record company 2L (let's call it "experimental"). In this picture you can see how well the color keys on the remote control allow the simple choice of different resolutions sound (5.1 DTS-HD MA, LPCM 5.1, LPCM Stereo, all in 192/24):  http://www.2l.no/epost/images/2L_Denon_screen.jpg

Also Stockfisch recently published in Pure Audio a disc by Sara K (5.1 DTS-HD MA, 5.1 PCM, PCM Stereo):
http://www.stockfisch-records.de/stckff/sf_sarak_d.html

In short, the system capability is really great and its potential too. We really hope that the race of the Pure Audio continues.

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Analysis and comparison of music audio files by using a specific software
(e.g. Adobe Audition)

First of all I want to thank Angelo for allowing me to write on the Audio Activity website.
I begin my collaboration with an article on how to analyze a music track from a CD by using a specific software (in this case, Adobe Audition, but it is also possible to use a free software like “Audacity” or similar ones, even if the results are generally less precise). If this kind of technical articles will be considered interesting I will be glad to propose other of them, on similar topics, obviously collecting suggestions from readers. What is the target of such analysis? The main purpose is to clarify some doubts on the recording and satisfy some “technical curiosities” on the peculiarities of the tracks themselves, especially when doing a comparison between different versions of a song (eg. the original version of a disc and its new remastered version). In fact sometimes the results of the analysis are not directly related to the results of the listening, and, conversely, most of the times, this kind of analysis gives very little information on the sound of the track itself. In fact, often he who analyzes (before listening) two similar tracks, or different versions of the same track, suggests himself considerations and conclusions which are then heavily modified or even distorted when the two tracks are heard in comparison. 
This is one of those cases where the ear is the undisputed judge: we know that the "listening pleasure" comes from a long series of factors, especially psychoacoustic, which are practically impossible to analyze analytically by instrumentation. 
On the other hand, there are other "technical information" contained in a music track that the ear can't discern, but that may be helpful to complete the knowledge of the track itself ... 
This said, let's start with the analysis of two different versions of the same track. I chose one that practically everyone knows: "Birdland" by Weather Report, included in their album "Heavy Weather". 
The original LP was released in 1977 while the CD was released in 1984. The disc I purchased at the time (from which I extracted the first track in analysis) was printed by CBS / Sony in Japan and has the catalog number CK34418. Then I recently bought on Amazon the box "The Perfect Jazz Collection -Vol.1" which contains a remastered version of 2010 of Heavy Weather -catalog number LC80162. From the latter I extracted the second track to analyze. 
In the following figure the first disc (the original, in plastic case) is at the top, the second (the remastered one, with paper envelope) is at the  bottom.

Listening to the remastered version I noticed that they did a good job. The overall timbre of the original CD was good, the dynamic was adequate (a little compressed, but not excessively) and the instruments were well located all along the stereo scene. A typical jazz / rock recording of the late '70s, with more positive than negative aspects, if we evaluate them with the critical skills and "audiophile" criteria that we all have developed over the  years listening to one format and the another (vinyl, cassette, CD, HD audio, etc ...). 
In the remastered version the tonal balance was a little revised: bass frequencies are much more present, both globally and in individual instruments (eg Pastorius's bass is more in evidence during his passages); mid and mid-high frequencies are a little softer than the original, but generally more "clear", probably thanks to an A / D converter more sophisticated than the one used almost thirty years ago. Of course, this consideration is valid only if the remastering was done using the original analog master or a copy of good quality, and not a digital acquisition of the analog master made earlier, but this we can not know. In most of the tracks the engineers adjusted at certain points certain passages particularly important to “highlight” them. Just to give an example: in the central part of Birdland, around 3'40 ", Shorter's sax is a bit more in evidence than in the original version. Finally, the overall dynamics is dramatically improved, which is quite unusual for a remastered copy, and considering the "havoc" we have witnessed in the last decade. Fortunately this was not done by simply raising the average level of volume (unfortunate trend of the so-called "loudness war "when taken to the extreme). 
While in the original recording the crescendos tend to flatten out during their increase, until you have a few decibels of dynamic between their beginning and their end, in the new version the increase occurs more gradually, better respecting the original dynamics of the tape (and this is easily verifiable via instrumental analysis, as we shall see shortly). In short, a good job that does not upset the original version but made it, in my opinion, even more  enjoyable.
 
And now we come to the instrumental analysis, carried out as mentioned with Adobe Audition and using only the analysis functions of this complete program (which means to use 5-10% of its capacity, since it allows an impressive array of features for treatment and processing of music that wouldn't be pertinent here). Let's see the waveform of the two versions of Birdland: In fig.1 the CD version of 1984, in fig.2 the 2010 remastering. 
(Note: in this analysis we consider only the track Birdland, but the considerations can be extended to the entire disc as the remastering is very homogeneous).

fig. 1

fig. 2


It may be noted that in the original version there are no clipped peaks, but the performance was a bit "sacrificed" by compression during the loud musical passages. Nothing unusual or negative: in 1984 was usual to proceed in this way.

In figures 3 and 4, I highlighted in red the areas of the right channel, in the first 2'40 "of the track, where the difference between the two versions is most visible. In the first area shown there is almost no difference (apart from a "small detail" that we will see shortly), while in the second and third areas we can see that dynamic was a bit '"recovered" compared to the first version and now the highest peaks of the two passages often touch the 0 dB.

fig. 3

fig. 4


Some peaks (fortunately very few) were "clipped" by a digital limiter, as can be seen in Figure 5, where in correspondence with one of these points I have amplified to the maximum the horizontal time axis to see the individual samples making up the waveform. I reported this just for didactic information, since these limitations are of a very small duration and cannot be heard even by the most trained ear. We are talking of a maximum of three to four consecutive samples for each of the peaks clipped, ie of a total duration of less than 100 microseconds, given that the sampling frequency of the CD is 44,100 Hz, and then each sample (the "dots "visible in the figure) has a duration of only 22.7 microseconds. There are many other "real" distortions from clipping, perfectly audible, which can be found even on some prestigious works ... (!)

fig. 5


I said that in the first area you can see a special feature. In fact, when observing well the two versions and moving your eyes from one to another, you can notice that between the two tracks the phase is reversed: in figure 6 I highlighted the upper front of the waveform of the left channel in the original version, which contains several peaks, which are "mirrored" in the waveform of the remastered version.

fig. 6

Again, this information should be considered only as a curiosity: first, because it is useless to repeat here the ancient and controversial issue on the audibility of the absolute phase in a music track, but mostly because we can not analyze the  original analog master, so there is no way to know if the waveform "correct" (so to speak) is that of the original version or that of the remastered one.... 
In conclusion here is an "overview" of the frequency response of both tracks. 
In Figure 7 and 8 you can compare the two graphs. Observing carefully the differences (ignoring the area up to 30-40 Hz, not significant), we have the confirmation of a major emphasis of the bass in the remastered version, in particular below 200 Hz; the  magnitude of the exaltation is about 4-5 dB between 50 and 100 Hz

fig. 7

fig. 8

Also the high range (around 20 kHz) is different: the original version is affected by the application of a very steep anti-aliasing filter, as were those used in A/D converters of the time, while the remastered version has a more "natural" roll-off. This confirms the use of a converter with very advanced digital filters that best meet the current "audiophile" approach. 
In Figures 9 and 10 we see finally the same frequency response of the previous figures, but here the horizontal scale is linear instead of logarithmic, so as to better highlight what happens at very high frequencies.

fig. 9
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fig. 10


My first analysis ends here. I hope you found it interesting.
 
Thank you all for your attention!
 
Quirino Cieri