franta-hg@0: /**
franta-hg@0:  * DJM-Fix
franta-hg@0:  * Copyright © 2020 František Kučera (Frantovo.cz, GlobalCode.info)
franta-hg@0:  *
franta-hg@0:  * This program is free software: you can redistribute it and/or modify
franta-hg@0:  * it under the terms of the GNU General Public License as published by
franta-hg@0:  * the Free Software Foundation, version 3 of the License.
franta-hg@0:  *
franta-hg@0:  * This program is distributed in the hope that it will be useful,
franta-hg@0:  * but WITHOUT ANY WARRANTY; without even the implied warranty of
franta-hg@0:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
franta-hg@0:  * GNU General Public License for more details.
franta-hg@0:  *
franta-hg@0:  * You should have received a copy of the GNU General Public License
franta-hg@0:  * along with this program. If not, see <http://www.gnu.org/licenses/>.
franta-hg@0:  */
franta-hg@0: 
franta-hg@1: #include <memory>
franta-hg@1: #include <iostream>
franta-hg@2: #include <chrono>
franta-hg@2: #include <thread>
franta-hg@2: #include <csignal>
franta-hg@5: #include <atomic>
franta-hg@1: 
franta-hg@1: #include "DJMFix.h"
franta-hg@2: #include "AlsaBridge.h"
franta-hg@2: 
franta-hg@5: static std::atomic<bool> run{true};
franta-hg@2: 
franta-hg@2: void interrupt(int signal) {
franta-hg@2: 	run = false;
franta-hg@2: 	std::cerr << "interrupt()" << std::endl; // TODO: do not mess STDIO
franta-hg@2: }
franta-hg@1: 
franta-hg@10: /**
franta-hg@10:  * The support for Pioneer DJ DJM-250MK2 (an external USB sound card / mixer) was added to the Linux (kernel) by these patches:
franta-hg@10:  *
franta-hg@10:  *  - https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/sound/usb?id=73d8c94084341e2895169a0462dbc18167f01683 (playback)
franta-hg@10:  *  - https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/sound/usb?id=14335d8b9e1a2bf006f9d969a103f9731cabb210 (recording)
franta-hg@10:  *  - https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/sound/usb?id=cdc01a1558dedcee3daee7e1802d0349a07edb87 (mixer setup)
franta-hg@10:  *
franta-hg@10:  * These patches are enough for playback and for recording from post CH faders.
franta-hg@10:  *
franta-hg@10:  * However this mixer is somehow incapacitated and if we want to record the raw signal from the PHONO or LINE channels,
franta-hg@10:  * we only get silence. This feature is important for DVS (Digital Vinyl Systems) setups where
franta-hg@10:  * the timecode signal from special control vinyls flows from mixer to the computer
franta-hg@10:  * where it is interpreted in a software like MIXXX and used for controlling the playback of files on our computer.
franta-hg@10:  * The signal (usually music) from these files flows back to the mixer and then to speakers and headphones.
franta-hg@10:  *
franta-hg@10:  * To make this work and enjoy all the features of the device we have bought, we need to tell the mixer that we
franta-hg@10:  * want the signal instead of silence on given channels. And this is the purpose of the djm-fix utility and
franta-hg@10:  * it is done by sending some magic packet to the mixer.
franta-hg@10:  *
franta-hg@10:  * Implementation of this magic in the AlsaBridge.cpp file is based on publicly available documentation
franta-hg@10:  * that can be found at <https://mixb.me/CDJHidProtocol/hid-analysis/handshake.html>.
franta-hg@10:  * 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)
franta-hg@10:  * and some magic bits. I wrote this standalone C++ program that talks with the mixer over MIDI SysEx messages and does the magic.
franta-hg@10:  *
franta-hg@10:  * When this program is started, it finds the mixer and makes it fully working.
franta-hg@10:  * It needs to be running all the time, otherwise we will get silence on the PHONO/LINE channels again.
franta-hg@10:  *
franta-hg@10:  * Install dependencies:
franta-hg@10:  *   apt install mercurial make pkg-config g++ libasound2-dev    # in Debian or Ubuntu (it will be similar in other distributions)
franta-hg@10:  *
franta-hg@10:  * Download djm-fix:
franta-hg@10:  *   hg clone https://hg.frantovo.cz/midi/djm-fix/               # primary source
franta-hg@10:  *   hg clone https://hg.globalcode.info/midi/djm-fix/           # or we can use this mirror
franta-hg@10:  *
franta-hg@10:  * Compile:
franta-hg@10:  *   make                                                        # we can skip this step, it will be compiled on the first run
franta-hg@10:  *
franta-hg@10:  * Run:
franta-hg@10:  *   make run
franta-hg@10:  *
franta-hg@10:  * Stop:
franta-hg@10:  *   press Ctrl+C
franta-hg@10:  */
franta-hg@10: 
franta-hg@0: int main(int argc, char**argv) {
franta-hg@5: 	std::string deviceName = argc == 2 ? argv[1] : "hw:1"; // FIXME: parse CLI options + automatic device search
franta-hg@10: 
franta-hg@2: 	signal(SIGINT, interrupt);
franta-hg@2: 	std::unique_ptr<djmfix::DJMFix> djmFix(djmfix::create());
franta-hg@5: 	std::unique_ptr<djmfix::alsa::AlsaBridge> alsaBridge(djmfix::alsa::create(djmFix.get(), deviceName));
franta-hg@1: 
franta-hg@2: 	alsaBridge->start();
franta-hg@2: 	while (run) std::this_thread::sleep_for(std::chrono::milliseconds(100));
franta-hg@2: 	alsaBridge->stop();
franta-hg@1: 
franta-hg@0: 	return 0;
franta-hg@0: }