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 Post subject: Re: Raspberry Pi
PostPosted: Thu Aug 20, 2015 11:32 pm 

Joined: Thu Aug 06, 2015 4:01 am
Posts: 27
Location: Iraklion
In principle, a relevant audio processor is not easily implemented in mobile devices as their battery consumption is the main interest when designing devices and applications for them. Some functions indeed should be integrated into a player, like compression and equalisation other than the native (alsa?) audio that is implemented in android. But any realtime processing other than just a simple FFT and matrix (call me equalizer) should be consuming so much battery that I don't know whether it worths the time. Hans knows best on this one.

Since that matter came into discussion, there are people (me included) that are truly frustrated by the constraints implemented into latest androids regarding maximum audio levels. Claiming that they "protect you hearing", most devices have limited their headphone reproduction levels down to minimal. Of course, that serves manufacturers well, as they don't have to implement a discrete high power audio amplifier inside their devices thus reducing costs, but will result in frustration od the user when a recording having wide dynamic range is reproduced through that system.

Stereo tool utilizes algorithms that could be trimmed down for maximum CPU efficiency, while not necessarily serving exquisite quality when e.g. it performs multiband processing or it performs advanced clipping. We just allow user to set a maximum audio level (e.g. -2DBFS) and then we use an AGC and maybe a 3-band compressor and some advanced clipper routines to keep audio level as close to preset dBFS level as possible without juicing off the battery. Quick adjustments like in basic mode should be all 13-year old kids should need to adjust volume levels to their needs, while protecting their ears.

I believe that this could sell well as almost all new phones and tablets could use such audio normalisation. Heck, even Google could be interested in such a project since in EU it is the LAW that audio levels in headphones should be kept below some preset audio level described by some EU standard I cannot recall right now.


https://www.google.gr/search?q=Maximum+ ... one+levels

Many ppl trying to get their phones to sing louder.

tl:dr

my thoughts is that a paid music player that promises maximum audio levels within EU limits could sell well on android.


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 Post subject: Re: Raspberry Pi
PostPosted: Tue Sep 22, 2015 12:10 am 
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I ordered a Pi 2 last Thursday and it arrived the next day. Have been running some tests on it to see how it performs.

The bad news is: It's really, really slow.
The good news is: After 2 days of work I managed to compile most of Stereo Tool on it, and I can run things on it - but usually only 1 or 2 filters simultaneously due to the slow speed. For example, I can run the declipper, OR I can run the AGC and a multiband compressor, but that's kinda it.

Now, the Pi has 4 cores, and Stereo Tool only uses 2. So there are some possibilities left. First thing I'm going to try to do is to make everything work as-is (some filters are currently broken and cause crashes). Once that's done I'll post a version here for people to play with.


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 Post subject: Re: Raspberry Pi
PostPosted: Tue Sep 22, 2015 4:45 am 

Joined: Fri Jun 15, 2012 1:32 am
Posts: 37
Very nice and thanks for working on making it work on the pi.

Whenever someone wants to hear music on an AM radio I always tell them to use Stereo Tools and I send them a file of custom settings for AM.

Having Stereo Tools work on the pi would definitely be beneficial as for the cost of the pi, a display and keyboard they will have stereo tools processing in a small package that can be taken most anywhere there is power to run it.

Wonder if maybe an older version of Stereo Tools would be easier to make work on the pi?

I still use version 6.21 as I didn't quite like the new interface of the newer version.


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 Post subject: Re: Raspberry Pi
PostPosted: Tue Sep 22, 2015 11:56 am 
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The newer versions use far less CPU load than the old ones, for many reasons. So, no. Also, the GUI on the new version works as-is on a Pi, the old GUI doesn't work on it at all and it would take a lot of effort to make it work.


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 Post subject: Re: Raspberry Pi
PostPosted: Tue Sep 22, 2015 11:17 pm 
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This is good: The NEON instructions on the Raspberry Pi resemble SSE on Intel a lot. Which means that I can convert at least some of my SSE-optimized code to the Pi2 with very little effort!

On my laptop the difference in performance between compiling with and without SSE-optimized code is about 25%.

I have written a wrapper layer with which (in just 2 hours!) I converted about half of my SSE2 code to the Pi2. It compiles... However running a full compile on the Pi2 takes several hours so I won't know if I made any errors before tomorrow morning. If things are still ok I will continue with the rest.


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 Post subject: Re: Raspberry Pi
PostPosted: Tue Sep 22, 2015 11:28 pm 
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I haven't tested this one AT ALL (I wanted to download a music player on the Pi that supports Jack but I had internet connection problems on my Pi so eventually I haven't tested it with audio at all). All I know is that:
1. It seems to run
2. The declipper beep gets played

http://www.stereotool.com/downloads/ste ... st_774-006

Note: This is for Raspberry Pi 2 with NEON support. The original Raspberry Pi is probably really to slow to do anything useful. NEON is currently only used for the FFT's, I'm working on optimizing the rest of the code (as I just typed earlier). "Ignore high frequencies" in the CPU & Latency settings does NOT work. Everything else should work.

Note: Start Jack with a big enough block size or you will get continuous hiccups. Also, use Jackd2; jackd does not work on the Pi!
I'm starting my Jackd2 server with:
jackd -d alsa -p 4096 -n 4

(Install jackd2 with: sudo apt-get install jackd2)


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 Post subject: Re: Raspberry Pi
PostPosted: Wed Sep 23, 2015 9:50 am 

Joined: Fri Jun 15, 2012 1:32 am
Posts: 37
Quote:
The newer versions use far less CPU load than the old ones, for many reasons. So, no. Also, the GUI on the new version works as-is on a Pi, the old GUI doesn't work on it at all and it would take a lot of effort to make it work.
Oh ok. I'll have to try the new interface and see if I can get used to it.

Many thanks for getting this to work.

Now I gotta look at how much the pi 2 costs along with whatever accessories I'll need then I can buy it and have a very small audio processor.

I can almost see this eventually finding use in radio stations that want a lot of processing ability without spending 1000s of dollars.


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 Post subject: Re: Raspberry Pi
PostPosted: Wed Sep 23, 2015 6:42 pm 
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Now with some NEON support (a bit faster - but not yet tested if it's completely accurate!)

http://www.stereotool.com/download/ster ... ETA774-007


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 Post subject: Re: Raspberry Pi
PostPosted: Thu Sep 24, 2015 12:37 am 
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Hm. Turns out that the speed of a Pi 2 is only about 2-2.5% of that of my laptop :( which means that we can't do much with it.


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 Post subject: Re: Raspberry Pi
PostPosted: Thu Sep 24, 2015 7:11 am 

Joined: Fri Jun 15, 2012 1:32 am
Posts: 37
Dang. Wonder if there's any other things similar to the pi that are more powerful?


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