Comprehensive audio demonstration/tutorial 6th Edition
The FIReverb Suite™ is the umbrella name for PureVerb™ and MultiVolver™
PureVerb™
MultiVolver™Is a virtual room
Finite Impulse Response (FIR) generator designed to
create high quality natural-sounding reverberberation to
be processed with:
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- creates natural-sounding, high-density, full frequency range 32-bit FIR reverberation using virtual microphones:
- mono (omni or cardioid)
- coincident stereo (cardioids)
- AB-stereo (variable spacing, also "wide AB")
- B-format (WXYZ)
- 5-channel (L, C, R, Ls, Rs e.g. for natural-sounding stereo to 5-channel upmix, interactive mic setup)
- the 5-channel implementation allows for individual microphone selection of:
- location
- aim
- type (cardioid, super-cardioid, hyper-cardioid, figure-of-8, special figure-of-8+ or omni-directional)
- setups can be saved and reused
- uses virtual mono or stereo sources. By creating several sets of mono or stereo source responses up to 8 sources can be used together with the MultiVolver™ since it will handle the relative calibration/scaling between responses automatically even for filters created at different times
- uses an FIR late reverberation algorithm similar to the one used in CATT-Acoustic™:
- is rather a virtual room impulse response creator than just a tool giving reverberation
- is based on physical principles and creates responses with a theoretically correct, with time increasing, reflection density avoiding the granularity in the tail created by many Infinite Impulse Response (IIR) algorithms
- is based on the experience from ten years of computer modeling and auralization of real rooms
- is used by Deutsche Grammophon together with a Lake Huron™ to enhance too dry recordings
- was used together with a Lake CP4™ to add reverberation to the music score at the World Cup in Football (Soccer...) final at Le Stade de France, 1998 (actually CATT-VRoom, the PureVerb™ predecessor)
- creates reverb for VR audio applications (together with Lake hardware, PureVerb™ can e.g. create all files required to run Lake AniScape™)
- supports several samplerates:
- 44100 Hz
- 48000 Hz
- 88200 Hz
- 96000 Hz
- 16 000 Hz (for Lake AniScape™ reverb)
- has a straight-forward interface with settings (*in octave-bands 125 to 16k Hz) for:
- room size
- virtual source location
- source directivity index*
- virtual microphone location
- reverberation time*
- diffusion*
- absorption distribution (uniform, audience or detailed*)
- reflection incidence distribution
- reflection density
- optional use of the Image Source Model for 1st order reflections
- optionally creates responses with the direct sound excluded and the original signal can be bypassed when mixing in the reverb
- has a large set of presets to promote realistic reverb settings and give good starting points for further fine-tuning:
- user expandable "Generic Halls" presets where average size and RT values can be taken from actual well know halls
- suggests reverberation time based on the volume and type of music (chamber music, opera, choir etc.) using curves of optimal ratios from literature (see fig below)
- suggests a volume based on the reverberation time and type of music (chamber music, opera, choir etc.) using curves of optimal ratios from literature (see fig above)
- suggests listener (or virtual
microphone) location based on the reverberation radius
of the selected hall (Close, Medium, Far)
- creates CATT PLT-files (2D plans, shaded 3D models and RT/Volume graphs) that can be viewed, printed and exported either via the included stand-alone CATT PLT-viewer or with CATT-Acoustic™ (from v7.2, also the demo version)
- creates a new PureVerb eXtended (PVX) single-file,
multi-input, multi-output, multi-microphone impulse response
format that also stores a PureVerb settings-file.
A PVX-file can be loaded by File|Open for examining the parameters used when creating the impulse responses, or to re-calculate the same basic responses after some changes in parameters. The PVX-format simplifies use of PureVerb responses in MultiVolver since only one file needs to selected for a complete set of filters. The PvxViewer shows the contents of a PVX-file, impulse responses, octave-band filtered impulse responses and decays. - optionally directly creates WAV-file format and includes a file-format conversion tool that converts Lake SIM-files to 16-, 24- or 32-bit PCM integer WAVs for use with other convolvers. Optionally creates WAVs in WAVE-EX format
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sample PureVerb™ screen-shots |
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sample 5-channel responses |
- examples of uses (all of these can be done in one step with auto-scaling):
- mono
mono reverb (1 x 1) - mono
stereo reverb/up-mix (1 x
2)
- mono
B-format reverb/upmix (1 x 4)
- mono
5-channel reverb/up-mix (1 x 5)
- stereo
stereo reverb/re-mix (2 x 2)
- stereo
B-format reverb/up-mix (2 x 4)
- 8-channel
5-channel reverb/mix (8 x 5)
- cross-talk cancellation of a binaurally recorded stereo file (2x2, CATT-Acoustic™ >= v7 can create cross-talk cancellation filters)
- 5-channel
binaural down-mix (5x2 or 6x2 for
5.1)*)
- n-channel Ambisonic
binaural down-mix (e.g. 4x2, 6x2
or 8x2)*)
- B-format
Ambisonic decode
for up to 8 loudspeakers
- each of the 8 inputs can have a gain to balance the mix
- Classic: each of the 8 inputs can be any of:
- a mono WAV
- the left of a stereo WAV
- the right of a stereo WAV
- stereo WAV (left/right mix)
- WCP: each of the inputs can be any of:
- a mono WAV
- a selected channel of a multi-channel WAV
- Classic: the output channels are either one mono WAV per channel or stereo WAVs assigned to successive pairs of outputs. WCP: output channels are either one mono WAV per channel or multi.channel WAV
- automatically handles calibration/scaling/overflow:
- separate mono
5-channel filters for each source
location can be created in PureVerb™
and they will be relative calibrated when the processing is made,
no wild trial runs required to check for overflow
- estimates filter gains and adjusts so that the output WAVs will not overflow. If it still happens in some odd cases (e.g. if the input WAVs have very low margins), it will be discovered and a safe second pass will be used
- gives a min "margin" value on the output WAV-files (similar to that of pro DATs and similar). If the resulting margin is too high, an automatic remake can be performed
- automatically handles delays from sources to microphones (if PureVerb™ or CATT-Acoustic™ responses are used, for imported responses initial delays should be included as initial zeros)
- utilizes Lake's
32-bit integer SIM-file format or PureVerb PVX for for the FIR filters:
- allows off-line tests to be made and subsequent processing using the same filters in a Lake Huron™ processor (or the other way around)
- each set of FIR-filters can have a base-name so that fast and safe filter changes can be made (requires only one name selection)
- can as well use measured FIRs via file conversion to SIM-format
- PVX load dialog:
- uses/creates 16-,24- or
32-bit PCM WAVs, optionally in WAVE-EX format.
- uses no temporary hard disk space at all, can thus convolve any length WAVs (as long as the resulting WAVs can be fit on the output disk)
- performs floating point convolution of long filters typically at 8x speed on an old 500 MHz PIII PC. Sample processing times with 88,000 tap FIRs (i.e. 2 sec reverb at 44.1 kHz) and 8 minutes of music:
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*) CATT-Acoustic™
>= v7 can create binaural room filters for various
listening room configurations
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convolutions |
time ; speed |
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mono reverb |
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stereo reverb |
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stereo reverb/re-mix |
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5-ch reverb/up-mix |
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5-ch reverb/up-mix |
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- real-time 2x5 zero- or low-latency processing in hardware at 44.1 or 48 kHz , as outlined above, requires:
- a Lake Huron™ with a minimum of 3 DSP-boards (12 Motorola DSPs) giving a latency of 160 ms (2 ms latency requires 5 DSP-boards, 20 DSPs)
- or (for 2x4 only actually):
- two Sony DRE-S777: 2x(11+11)=44 Sony custom DSPs total (assuming the required second DSP boards also contains 11 DSPs)
- two Yamaha SREV1: 2x32=64 Yamaha custom DSPs total
- has an integrated Ambisonic decode filter creator:
- optional user-supplied shelf- and inverse speaker filters
- energy and velocity vector graphs
- save/load rigs or complete filter setups
- includes a WAV-file player with single, A/B and play-list options
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sample MultiVolver VST/WCP™ screen-shots |
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sample MultiVolver™ classic screen-shots |
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signal flow graphs, principles |
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Ambisonic decoder details |