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In Reply to: RE: j river room correction not convolution.. posted by Les C on June 29, 2012 at 03:34:21
I'm not sure what your point or question is.
Convolution is a mathematical operation that can be performed on two audio signals, e.g. an audio channel and an impulse response resulting in a modified audio stream. By selecting the appropriate impulse file or files (e.g. different ones for each channel) one can do various things: room EQ, speaker correction, speaker alignment etc. A convolution engine is completely general purpose.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
Follow Ups:
I'm not sure what your point or question is
JRiver has a DSP studio.
One day they added a module “Room correction”
Thss allows you to add a delay for each channel and a volume level.
Basically placement correction.
Recently they added DRC.
As “Room correction” was already used inside DSP studio they called it “Convolution”.
The Well Tempered Computer
Right but they seem to be calling "convolution based equalization" and "room correction" the same thing.
Not all equalization is done with convolution.
Not all convolution is room correction.
Not all room correction is convolution.
Do you have to build a custom room for J River for their room correction to work?
Cheers,
Presto
I was using cPlay, which allowed VST plugins. I used the free VST EQ that you suggested to take out two peaks in my room response, one at around 40 Hz and the other around 125 Hz. I was able to get a reasonably flat response from 28 Hz up to 1 kHz this way, but I expect I can do better. Doing this room EQ provided a significant improvement in sound balance as well as imaging. (In a better room this might not have been so important.)
I got HQPlayer, because it will play DSD files through my Mytek DAC. It will also upsample PCM files to DSD128 and this produces significantly better sound than sending PCM directly to the Mytek, even if it is native 192/24 PCM. (Don't ask me why, it's just so. Jussi Laako who wrote HQPlayer knows his stuff!) HQplayer has a "convolution engine" that takes mono WAV files of impulses and convolutes these with each audio channel, but no VST plug in.
What I did was to use an audio editor to create a mono file consisting of two seconds of silence. Then at the first sample I put in a 0dBfs digital "impulse". I then ran this file through my editor and applied my VST room EQ plugin. The result was a new impulse file that I could use with HQplayer. I presume the same method would work with JRiver or anything else. As it happens, the VST plug in I used is IIR, but after two seconds of impulses the impulse response of my "room eq" settings is below the threshold of 24 bit reproduction. Hence, I am getting the same response as I would have (modulo 64 bit floating point calculations) using the VST plug in directly.
To generate these impulse files, I used Soundforge, which is available for free trial. I presume other free editors such as Audacity have the same ability to generate impulse files and support VST plug ins.
Incidentally, when playing DSD files I am stuck without room correction unless I want to convert these to PCM, e.g. first convert them to DXD. However, it is possible that in a future version of HQplayer there will be the ability to do room correction on DSD files without lowering the sampling rate below 2.8 MHz. (Whether my CPU will be fast enough to do this in real time remains to be seen. It will do room correction on DXD files and upsampling to DSD128 in real time, using about 70% of both cores of my first generation 3.2 GHz i5.)
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
Tony,
Is HQPlayer good just for converting file formats during playback, or can it also save the converted file for future editing? Let us say I want to convert a DSD file To hi-res PCM, save it and then retrieve the PCM file for equalization and saving it again. Can this be done?
What about conversion from PCM to 64-bit floating point and vice versa?
Thanks, Eli
HQPlayer takes as input files and produces an output stream using the Windows audio stack (WASABI) or ASIO. It doesn't do file to file operations. Presumably the output of the program can be captured in some way and sent to a file, but this is not part of the software. (For example, if HQPlayer accesses an SPDIF based sound card one could loop back the SPDIF output stream and record it. This might not be convenient or fast, but it would work, at least for PCM.)
Integer PCM is easily converted to double precision (64 bit) floating point PCM. For example, this can be done by Soundforge 10 which supports this format.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
Thank you indeed.
I guess I will do first some experiments on the cheap, and then possibly opt for specialized software. I can use Audiogate to export to a different format, even to 32 bit FP. Then apply my own RIAA filter I wrote in Mathcad and add some gentle low-pass filtering. Mathcad has some rudimentary FIR and IIR filters in FFT or convolution, but I do not trust these, as they do not mention any sound quality considerations.
Then again, I can be lazy and bypass DSD entirely. Use the Korg in 192/24 PCM and then export it to 192/32 with audiogate. The program does not perform any calculations when the sample rate stays the same. After filtering in 32 bits I may save it as is or reduce the bit depth to 24 with dithering. I bet this simple outline can sound as good if not better then my original grandiose plan.
Thanks again, Eli.
thanks Presto :).i'm just surprised that with 50$ you get great playback and room correction and i had to go through a lot of software just to go back to jrmc, click a button, adjust a few sliders and be done with searching for the right software.
*sigh*
Edits: 06/29/12
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