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/**
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* DJM-Fix
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* Copyright © 2020 František Kučera (Frantovo.cz, GlobalCode.info)
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, version 3 of the License.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <memory>
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#include <iostream>
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#include <chrono>
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#include <thread>
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#include <csignal>
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#include <atomic>
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#include "DJMFix.h"
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#include "AlsaBridge.h"
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static std::atomic<bool> run{true};
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void interrupt(int signal) {
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run = false;
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std::cerr << "interrupt()" << std::endl; // TODO: do not mess STDIO
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}
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/**
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* The support for Pioneer DJ DJM-250MK2 (an external USB sound card / mixer) was added to the Linux (kernel) by these patches:
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*
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* - https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/sound/usb?id=73d8c94084341e2895169a0462dbc18167f01683 (playback)
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* - https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/sound/usb?id=14335d8b9e1a2bf006f9d969a103f9731cabb210 (recording)
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* - https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/sound/usb?id=cdc01a1558dedcee3daee7e1802d0349a07edb87 (mixer setup)
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*
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* These patches are enough for playback and for recording from post CH faders.
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*
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* However this mixer is somehow incapacitated and if we want to record the raw signal from the PHONO or LINE channels,
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* we only get silence. This feature is important for DVS (Digital Vinyl Systems) setups where
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* the timecode signal from special control vinyls flows from mixer to the computer
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* where it is interpreted in a software like MIXXX and used for controlling the playback of files on our computer.
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* The signal (usually music) from these files flows back to the mixer and then to speakers and headphones.
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*
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* To make this work and enjoy all the features of the device we have bought, we need to tell the mixer that we
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* want the signal instead of silence on given channels. And this is the purpose of the djm-fix utility and
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* it is done by sending some magic packet to the mixer.
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*
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* Implementation of this magic in the AlsaBridge.cpp file is based on publicly available documentation
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* that can be found at <https://mixb.me/CDJHidProtocol/hid-analysis/handshake.html>.
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* This page pointed me to the proper hash function (according to the constants, it is bit uncommon but publicly known Fowler–Noll–Vo hash function, FNV)
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* and some magic bits. I wrote this standalone C++ program that talks with the mixer over MIDI SysEx messages and does the magic.
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*
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* When this program is started, it finds the mixer and makes it fully working.
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* It needs to be running all the time, otherwise we will get silence on the PHONO/LINE channels again.
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*
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* Install dependencies:
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* apt install mercurial make pkg-config g++ libasound2-dev # in Debian or Ubuntu (it will be similar in other distributions)
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*
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* Download djm-fix:
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* hg clone https://hg.frantovo.cz/midi/djm-fix/ # primary source
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* hg clone https://hg.globalcode.info/midi/djm-fix/ # or we can use this mirror
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*
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* Compile:
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* make # we can skip this step, it will be compiled on the first run
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*
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* Run:
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* make run # in most cases
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* build/djm-fix 'Pioneer DJ.*' # or provide custom name pattern (regular expression) to select the proper card
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*
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* Stop:
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* press Ctrl+C
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*
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* Look for updates in the Mercurial repositories and at <https://blog.frantovo.cz/c/387/>.
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*/
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int main(int argc, char**argv) {
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try {
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std::string cardNamePattern = argc == 2 ? argv[1] : "Pioneer DJ.*";
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signal(SIGINT, interrupt);
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std::unique_ptr<djmfix::DJMFix> djmFix(djmfix::create());
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std::unique_ptr<djmfix::alsa::AlsaBridge> alsaBridge(djmfix::alsa::create(djmFix.get(), cardNamePattern));
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alsaBridge->start();
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while (run) std::this_thread::sleep_for(std::chrono::milliseconds(100));
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alsaBridge->stop();
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return 0;
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} catch (const std::exception& e) {
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std::cerr << "ERROR: " << e.what() << std::endl; // TODO: do not mess STDIO
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}
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}
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