P. LYUBIMOV, Bobruisk, Mogilev region
Radio, 2002, No. 1
After installing the TDA3810 processor, for example, in an AU receiver with a decoder Dolby Surround Pro Logic and multi-channel AC, the monophonic TV soundtrack acquires a noticeable "depth". This effect occurs due to the presence in the decoder for the rear signal of a time delay of several tens of milliseconds, which is absent in a conventional stereo processor. The author talks about installing the processor in the Technics SC-CH60 audio system used in conjunction with a TV and VCR.
The article described a device based on the TDA3810 sound processor, which allows you to get pseudo-stereo sound with a monophonic TV broadcast signal. This mode of operation of the microcircuit provides additional features when using it and in a more complex audio system.
The essence of the proposal is to install the TDA3810 chip in a mini-system, receiver or amplifier capable of playing stereo tracks through a DSPL (Dolby Surround Pro Logic) decoder with a multi-channel amplifier and a set of speakers. Despite the fact that the pseudo-stereo signal is very far from the DSPL format, the introduction of the TDA3810 into such a path creates a rather effective spatial sound picture.
The processor scheme is shown in fig. 1.
It differs from the typical one given in the absence of elements for providing the "Extended stereo" mode (this mode is not used in this device), as well as indication LEDs. Pin 12 of the DA1 chip is connected to a common wire, which corresponds to the "Pseudo-stereo" mode.
Sketch printed circuit board processor and the arrangement of elements on it are shown in Fig. 2. The device uses MLT-0.125 resistors, capacitors C10 - C13 - K50-35, the rest - KM-4, KM-5.
The processor board is installed in the "Stereo Sound Processor SH-EH60" block of the mini-system. All processor connections are made to the switching board located at the rear of the case. Entrance U ynp is left free. The processor is powered from the +13 V power supply of the equipment. The left and right channel inputs are connected to standard "VCR INLUR" connectors. To do this, you must first unsolder the leads of the elements C706, R710 and C705, R709 (designations on the mini-system board) from the points of connection to the connectors. The wires of the inputs of the left and right channels of the processor are soldered into the vacated holes. Soldered conclusions are connected: C706 - with R710, and C705 - with R709. Solder the wires of the processor outputs of the right and left channels, respectively, to the connection points. The location of the holes for connection on the switching board is shown in fig. 3. Next, the board is fixed with a self-tapping screw on the stand on the right side of the case (Fig. 3).
Thus, after the work done, the VCR input is now intended for connecting sources with 
monophonic path (the signal is fed to the left and right channels) - TV, VCR, etc. Stereo signals can be fed to the VDP and EXT inputs of the minisystem.
If you need to connect a source that works in both mono and stereo modes, for example, a Hi-Fi VCR, then the processor must be supplemented with a two-position switch, which is installed on the rear wall of the SB-EH60 unit. In the "Stereo" mode, the switch must close the Ucontrol input to a common wire, in the "Pseudo-stereo" mode, leave this input free. The switch is also required if the processor is installed in a machine that has only one input.
When listening, the excellent work of the processor as part of the Technics SC-CH60 mini-system was noted. The sound in DSPL mode is especially impressive. If the decoder does not respond to a mono signal, then when the processor is turned on, all speakers create a noticeable spatial distribution of sound.
According to the above method, it is easy to equip the TDA3810 processor with another music center, receiver, amplifier with a DSPL decoder.
LITERATURE
1. Brylov V. Stereo sound in ZUSCT. - Radio, 2001, No. 2, p. 9 - 11, 14; No. 3, p. 10 - 12.
2. Sokolova N. Sound engineering "home theater". - Radio, 1997, No. 5, p. 17 - 19.
3. TDA3810 surround sound processor. - Radio, 2001, No. 2, p. 49 - 51.
What are the new promising developments in the field of surround sound?
The epoch of the approval of standards "for centuries" has long sunk into oblivion. And if the path of stereo to the cinema took more than half a century - before Mr. Dolby undertook the total transfer of theaters to a multi-channel scheme, this was only a farewell to the slow passage of time. The progress and acceleration of the rhythm of life, as well as new techniques to stimulate the market, have led to a truly computer race in the home theater industry, which resulted in a rapid (and almost annual) change in sound formats for home use. The passion for completing the home cinema with two additional rear center channels (Dolby Digital EX, DTS ES Discrete / Matrix) has not died down yet, the proper number of DVDs with support for these sound systems, as last year was marked by a further expansion of the "model" range - devices with DTS 96/24 and Dolby Pro Logic II went into the series. Below we will try to dot the “i” in this matter, telling in detail who and why they can be useful (note that this review does not pretend to compare two standards that are different in essence and purpose, but only deciphers their positive and negative sides).
Ten years have passed since the theatrical introduction of Steven Spielberg's brainchild, DTS sound for cinema, and the collection of home formats has already amounted to: the original DTS 5.1 (with variable bitrates 768-1500 kbps), DTS Neo: 6 (decomposing two-channel schemes into multi-channel ones), DTS ES 5.1 Matrix (with a rear center signal mixed into the rear) and DTS 6.1 Discrete (with a dedicated rear center signal). And although the latter, with the accepted bitrate even at 768 kbps, provided the best available sound quality at home, the studio went further by approving DTS 96/24 - a six-channel standard with parameters from DVD-audio discs - 96 kHz sampling, 24-bit bit depth, which is worth much above traditional 48 kHz and 20 bits in all theater-accessible formats.
The company calls the main advantages of DTS 96/24:
And, although the decoding requirements include the DTS 96/24 logo, that is, the ability of the processor to recognize the new standard, conversion to regular DTS is possible on most DTS-compatible devices, and those that have 96/24 digital-to-analog converters in all channels , can, in most cases, correctly reproduce new sound. This possibility is not advertised, but is easily verified in practice.
The reception of the format in the US has not been the best, but a number of titles of music of different genres have been released recently (many releases appeared in April 2003):
Queen: Greatest Video Hits 1
Queen: The Game
Queen: A Night at the Opera
Rythmedia Tribe
Gorsby/Nash: Another Stoney Evening
Sheila Nicholls
Megadeth: Peace Sells...But Who's Buying?
brazilian jazz
Brazilian Bossa
The Fabulcus Thunderbirds: This Night in L.A.
Frank Zappa
Most of these are combo DVD-A releases containing 5.1 MLP DVD-audio tracks, DTS 96/24 for conventional theater systems and 2.0 PCM for conventional stereo fans.
So far, only one film in this format has been released - this is "Tomb Raider" of the second region, made in Italy - soundtrack in DTS 96/24 there is only in the Italian dub.
Such an approach is completely unjustified for the user - DVD-A players today start at $200 - and even 5.1 96/24 sound in DVD-A format is without question better than compressed DTS of the same bit depth. The poor list of released titles and their musical focus makes DTS 96/24 the lot of highly specialized sound maniacs - the advantages of this approach in the theater could seriously concern fans of the "very best", but, probably, the studio's capabilities became a stumbling block, because reworking the original masters is a matter of time consuming and thankless, so sound engineers are usually limited to "quick" adaptation of standard DTS / DD movie versions for home use. Quite "unconventional" is the approach of DTS Entertainment, which specializes in such releases - often, all attention is paid to DTS-mastering of music, and the DVD-A section is deliberately worsened: the difference between them, as a result, is leveled, but it is worth putting a high-quality recorded DVD-A disc , and everything falls into place (but more on that below).
The last good news about the format was its support on a number of digital radio stations - their broadcasting in DTS 96/24 seems to be a very winning move in moving to the market.
Unlike the next invention of the bicycle in DTS, the healthy conservatism of Dolby did not allow new discrete standards to be fenced - and heavy artillery was used in the form of an “upgrade” of Pro Logic to version 2.0. The promises were tempting - a complete translation of stereo sound into 5.1 with a quality (attention!) comparable to Dolby Digital 5.1. Given the masses of old recordings on VHS, LD (of which over 50,000 titles have been released alone), hundreds of DVDs with DD2.0 sound (anime, classic, series), and the ardent desire of individual cinephiles to play CDs through all their speakers, this decision could really shock the market.
In the beginning, two variations were introduced - Dolby Pro Logic II Movie for film programs and Dolby Pro Logic II Music for music, then Car adaptations appeared, and recently Virtual Speaker technology was introduced, which allows you to create a three-dimensional field with just two speakers. Dolby Headphone is also based on this principle. There is also a Matrix system, which is included in the processors by default, and works on mono-material. Note that before the release of Pro Logic II (and DTS Neo: 6, which, however, turned out to be very mediocre), the palm in native formats for decomposing 2.0 into 5.1 schemes belonged to Logic 7 from Harman, most successfully implemented in Lexicon processors. However, the highest price for such devices, as well as, in general, not the most perfect algorithm, did not honor this - devices with Pro Logic II are now available for sale at a price of $300.
When working on cinematic material using special Dolby 2.0 algorithms, the sound is decomposed into a multi-channel 5.1 scheme with the full use of all speakers, and, as stated, is quite close in quality to DD5.1. When choosing music, you can level out the most important defect of Pro Logic's past - an overestimated level of the center channel. Using the Center Width parameter, this indicator is calibrated to match the front speakers. Two more functions - Panorama (perspective adjustment) and Dimension (balance) allow you to quite accurately rebuild the translation of stereo music into a three-dimensional scene. In this case, Pro Logic has taken a big step forward compared to the similar content of DTS Neo:6, in which the detrimental effect of the center channel on the music is still strongly felt.
It's nice that the format does not put forward any requirements for the source and the sound recorded on it, but official support for the Pro Logic II flag (for example, on games for the Nintendo Game Cube) can mean optimization and better quality. Today, the vast majority of manufactured receivers and processors support Dolby Pro Logic II.
The comparison was made using next system: Denon A1SR receiver, B&W CDM acoustics, player - Pioneer 757Ai.
DTS 96/24 material used Queen: The Game, Queen: A Night at the Opera, and Pro Logic II was tested on a variety of CD material (from Stray Cats, Metallica to Wagner and Beethoven) and 2.0 DVDs (" The Man Who Wasn't There R5, Escaflowne Series 1-4 R1, etc.).
We couldn't test DTS 96/24 in the cinema version, because even with the right version of Tomb Raider, the dubbed track can hardly be considered a full-fledged sound - so we'll wait for the DVD R1 with cinematic material in this format. Of the music presented, DTS 96/24 showed good inclinations in terms of volume and detail, sharply surpassing conventional DTS-musicians. However, even the poor quality DVD-A master sounded slightly better on these discs, not to mention the newer DVD-A discs. Queen's tracks were distinguished by audible sound compression - alas, it is physically possible to overcome the shortcomings of compression only by a radical increase in bitrate. But even in this form, the potential of the format for home cinema was clearly noticeable - that's where the ground would be for building a new "SuperBit'a 96" or similar titles - impeccable detail and the stranglehold of localization - exactly what the slightly relaxed modern formats lack for at home versus theatrical SDDS, for example.
As for Dolby Pro Logic II, in the music mode on regular CDs, it showed a wealth of talent for turning stereo into a multi-channel circuit, building up the soundscape in subtle and detailed ways - sometimes a little more carefully than we would like, but very naturally and impressively: this is exactly what , which the fans of Logic 7 wanted, only in a more competent execution. Naturally, this option not at all for purists, as the timbre colors of the sound shift, and the stereo panorama sometimes becomes unstable, but it is still a significant step forward compared to previously proposed algorithms from other studios. The vast majority of owners of multi-channel systems will prefer Pro Logic II for the "add-on" over the usual compact. From the cinema side given format also impresses even the worldly-wise, almost falling short of DD5.1, but great shaping the special effect component in all channels - the only complaint is the slightly boomy central channel: creating the necessary volume, it often muffles the dialogues. However, this can be easily corrected by adjusting the balance of the system.
| Format | Advantages | Flaws |
|---|---|---|
| DTS 96/24 | - high potential for film sound - good quality musical material comparable (but not equal) to some DVD-A discs - the ability to play on a non-certified DTS decoder | - a small number of titles, the almost complete absence of films in the format - musical potential does not reach the best samples DVD-A discs - not supported by all modern receivers |
| Dolby Pro Logic II | - ideal per-channel decomposition of 2.0 sound in 5.1 - both for cinema and music - the ability to use on any 2.0 and 1.0 material - the broadest support by hardware manufacturers | - quality DD/DTS 5.1 mastering, still better - loudness of the center channel in theater mode |
It is unlikely that the DTS 96/24 will have a bright future, but it will, of course, win its place under the sun in high-end complexes. Another thing is Pro Logic II - buying a new receiver, you are doomed to have such an opportunity, and after listening to old cassettes with this "feature" you are doomed to use it further - a really nuclear thing. Once again, Dolby showed its mass approach, and DTS - chamber. Well, to each his own.
2 answers
TL: dr; it's possible it's possible; it might be easier if you are a programmer.
Since the encoded information is just a stereo pair, there is no guaranteed way to detect a Dolby Pro Logic II (DPL2) signal unless you specifically store your own metadata saying "this is a DPL2 file". But you can probably make a pretty good guess.
All older analog Dolby Surround formats, including DPL2, preserve the surround information in two channels by inverting the phase of the surround or surround sound and then downmixing it with the original left and right channels. Dolby Surround decoders, including DPL2, attempt to recover this information by inverting the phase of one of the two channels, and then look for similarities in those signal pairs. This is either done trivially, as in Dolby Surround, or these similarities are artificially shifted to go much further left or right, or left or right, as in DPL2.
So the trick is to determine if important data is stored in the surround channel(s). I'll draw a method for you that might work and I'll try to express it without writing code, but it's up to you how to implement it and to your liking.
I wrote this algorithm in such a way that you can perform each of these steps with a special command in . If you want to be kinder, instead of doing the RMS/peak sox step, you can run the program and check your LUFS levels against tolerances. If you want to be even more attractive by creating Surround and Center files, you can filter out all frequencies above 7 kHz and focus on them just like a real DPL2 decoder.
To keep this algorithm simple, I sketched it entirely in the amplitude domain. The calculation of the SurroundLevel file is likely to be much more accurately done in frequency domain if you know how to calculate the magnitude and angle of the FFT bits and you are using windows from 30ms to 100ms. But this cheapo version above should get you started.
Last warning. AAC is a modern psychoacoustic codec, which means it likes to play games with stereophasing and rendering to achieve compression. So I think it's likely that the simple act of encapsulating DPL2 into an AAC stream will likely nest some of the images present in DPL2. To be frank, neither DPL2 nor AAC belong anywhere in this pipeline. If you must save an analog stream originally encoded with DPL2, do so in a lossless format such as WAV or FLAC, not AAC.
At the time of this writing, the operating concepts of Dolby Pro Logic (I) are . These basic concepts still apply to DPL2; operating concepts for DPL2.
If a file has more than one channel, you can assume with some confidence that they are being used for surround sound purposes, although they may just be multiple tracks. In this case it falls to the game system to do with the channels as it "thinks" best. (unless the file header says what to do)
But your file is stereo. If you want to know if it's a virtual surround file, you can look in the encoder field header to see which encoder was used. This may help somewhat, although not much. The main encoder field is left blank, and second that the encoder does not have to be the same as the recoder that mixes the surround data. That is, the recorder will first create raw PCM data and then feed it to some encoder to create compressed file. (AAC or whatever) In addition, there are many applications and versions that can change, so the encoder field can keep track of everything that would be annoying.
However, you can deduce with more than 60% certainty whether something is a virtual environment or not by examining the data. It will be an advanced DSP and even machine learning could be involved for speed. You will need to find out if the stereo signals contain certain HRTF (Head Related Transfer Function) features. This can be achieved by examining intensity and delay differences between the same sound appearing in the time domain and the harmonic characteristics (characteristic changes in frequency) in the frequency domain. You will need to do both, because one without the other can just tell you that something is a very good stereo recording, not a virtual environment. I don't know if there are any HRTF functions that have already been mapped, or if you would need to do it yourself.
This is a very complex decision that takes a lot of time to get right. Also performance will be problematic.
With this method, you can also turn down the stereo mix down to near-original surround channels. But other methods are used to convert stereo to ambient, and they sound good.
If you are determined to do this kind of discovery, dedicate half a year or more of hard work if there are no HRTF features, a few weeks if there are, brace yourself for a lot of stress and I wish you the best of luck. I did something similar. This is a killer.
If you want to use a turnkey solution then your question is not answered unless the header provides you with an encoder field and the encoder is different and is only known to be used to convert surround to stereo. I don't think anyone made it from the actual data as I described, or if they did, it's part of a commercial product. Doing what you need is not usually required, but it can be done.
Ow, BTW, try googling HRTF inversion, it might provide some help.
