Hi, >> P.S.: I believe that the “live” film recording is mostly about recording >> some form of ambience, the final sound being mixed in the studio.
Actually "live" film recording is now mostly actually about trying to acquire some usable dialogue. It is hard and expensive to recreate this, and the actors' performances, in post-production. ADR is not "automatic" dialogue replacement, though it is usually automated to ease the tedium and complication of multiple takes. Ambiences are usually recorded either when the rest of the crew have left and the set is empty, or recorded elsewhere. Some spot effects may also be gathered during a take or in dead time afterwards. >> In this sense I don’t quite understand what you mean with “large scale >> events”. A live recording of an open air concert? Ambisonics “alone” won’t >> be good for this, granted. A large scale event is one in a large, or very large space with a large dispersed audience, e.g a large concert or exhibition space requiring sound reinforcement, a football stadium, a city centre, a harbour, an outdoor music or other festival, a large outdoor firework display (such as New Year's Eve, an Olympic Games. Ambisonics is not so useful in these cases, as one cannot ensure coherent arrival of sound from widely spaced loudspeakers over a large area. In large spaces, time delays become very noticeable. Sound has a finite speed. As I said, "things like d&b's Soundscape, L'Acoustics LISA, Timax, and Astro Spatial Audio are all based on the ideas of Delta Stereophony". This was started in East Germany in the mid 1980's, mostly aimed at large opera and concert halls. The idea is that the stage position of performers can be augmented by a number of loudspeakers in the hall, each fed with mixes of an appropriate signal per performer with level and delay modification. At around the same period, or perhaps a bit later when digital delay lines became common and more affordable, it became common in public address systems to have loudspeakers in the hall, which were delayed so that their time of arrival coincided with that of sound from the main PA system, or even that the entire system was delayed to match the position of the performers. Mostly this was done to provide good coverage over the whole area, rather than it being loud where the front PA was pointed and quiet at the back and sides. It needs very careful placing of appropriate speakers, and careful adjustment of gains and delays throughout the whole system. The delay times are only right in very few places and never right everywhere. It was mostly a form of distributed mono. In many cases the sound system is too wide to cover the front rows, and an additional low key "front fill" system is added. This in turn needs to be delayed. Timax, which is at least 20 years old, was among the first modern system to attempt to do this on a larger and more controllable scale. It is still widely used, and was the first to attempt a "track the actors" system where position data automatically controls the audio image, rather than an operator having to juggle to follow several performers. WFS is basically a similar amplitude/delay implementation using many more closely spaced speakers, as Augustine implies not really practical even for permanent installations and totally impractical for one off events. Most existing installed systems are horizontal lines of drivers around a space, as a full implementation would require entire walls, ceilings and floors of drivers. Interestingly the same sort of processing is used in "line" and "beam forming" arrays of loudspeaker drivers. The current "Delta Stereophony" systems from d&b, L'Acoustics, Timax, and Astro all use a proprietary hardware DSP box controlled by a computer or DAW plug-ins, which is sent a large number of signals from a mixing desk or DAW. They are mostly used to provide greater coherent coverage of a frontal image sound over a large area, with a sense of "immersion" over that area. It has been admitted by a d&b spokesman that attempting to use them with widely spread percussive sounds would produce a lot of clatter. Interestingly it is claimed that a satisfactory sound level over a good can be attained with an overall reduction in absolute sound level and the spread to outlying areas and neighbourhoods. Of course it is not perfect. Nothing ever is. Basic audio engineering practices still apply. You have to keep the loudspeakers at a decent distance from the nearest listener. The system has to be well calibrated. d&b and LISA are built on top of their overall system control. Timax and Astro are system agnostic. Other systems are possible, as Augustine suggests, though at present none can compete with the industrial and commercial muscle of major players like d&b, L'Acoustics and Dolby. The capability of modern DSP chips could enable incorporation of any of these into digital mixing desks, though making something user friendly and understandable is a huge challenge. Ciao, Dave Hunt The below is edited in the interests of succinctness. On 2 Mar 2019, at 17:00, sursound-requ...@music.vt.edu wrote: > From: Augustine Leudar <augustineleu...@gmail.com> > Subject: Re: [Sursound] Sursound Digest, Vol 127, Issue 9 > Date: 2 March 2019 13:31:54 GMT > To: Surround Sound discussion group <sursound@music.vt.edu> > > > For real 3D audio in large scale events no system that uses peripheral > speaker arrays present a truly immersive solution as they overlook > proximity. At best they offer 2 and a half D audio working on the surface > of a sphere with limited potential to get sounds to get close to the > listener. WFS offers proximity in form of focussed sources but uses far too > many speakers to be practical for large scale one off events. I find it > hard to see how systems with far less speakers can be based on WFS as the > gaps between speakers present enough spectral problems for high frequencies > even in wfs how can this be done on only 30 speakers in a huge space. The > only practical solutions seems to be a form of dbap with speakers inside > the array. Do any object based solutions have the ability to map to these > kind of arrays ( say with speakers inside seating etc) - would be > interesting. > > On Friday, 1 March 2019, Stefan Schreiber <st...@mail.telepac.pt> wrote: > >> >> P.S.: I believe that the “live” film recording is mostly about recording >> some form of ambience, the final sound being mixed in the studio. >> >> In this sense I don’t quite understand what you mean with “large scale >> events”. A live recording of an open air concert? Ambisonics “alone” won’t >> be good for this, granted. >> >> - - - - >> >> Citando Dave Hunt <davehuntau...@btinternet.com>: >> >>> The desire for "immersive" audio is certainly growing, and ambisonics is >>> immensely useful, but it is not really right for large scale events where >>> things like d&b's Soundscape, L'Acoustics LISA, Timax, and Astro Spatial >>> Audio seem to be the main competitors. These are all based on Delta >>> Stereophony, which can be regarded as a cut down form of Wavefield >>> Synthesis. >>> >>> >>> >>> Ciao, >>> >>> >>> >>> Dave Hunt _______________________________________________ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit account or options, view archives and so on.
