I'm doing some feasibility research with regards to a (large) book cataloging project. Any help would w/r/t good sources of information would be appreciated but the things I would specifically like to know are:
1.)does python have any modules for use with barcode readers (preferably USB)? What other programs are available for reading barcode information?
2.)This may be better answered with a few sources of information, but what kinds of things should I look for in a barcode scanner, especially if I'm looking to scan, specifically, a lot of barcodes on books.
3.)This may also be better answered with a few sources of information, what kind of information is stored standard in a book's barcode.
I know this is relatively off-topic, but any help would be greatly appreciated.
You don't need any - most USB barcode scanners emulate a keyboard - if you scan a barcode it simply sends a series of key presses representing the numbers (or text if it's a more advanced barcode encoding) encoded in the barcode. Most scanners are pretty configurable so you could configure it to send a special character before the barcode data, then listen for key presses and if it matches that special character, then focus on the input field where you want the barcode data.
It depends a lot on what you're trying to do, the furniture where it's being done, etc. I was involved in a reasonably large rollout of general purpose scanners (happened to be these) - it worked fine for what we were doing and there weren't any drivers to install or anything...the only thing that needed to be done was the stand that came with it was bolted to the desk next to the PC - and that wasn't our concern!
A typical book barcode encodes the book's ISBN.
Are you making a python web-app or a client application? Unless you're looking for specialized bar code scanning functionality it doesn't really matter since the input from the scanner appears like keyboard entry (sometimes prefixed with a special input character), so you just have to have a way of listening to the keyboard input and catching that special character.
Related
I am in need of library that can read barcodes from usb connected barcode scanners. I have done my research but there happens to be one barcode api which was recommended which is https://github.com/libusb/hidapi hidapi but it happens to be written in C++ and I do not know how to use it.
Any suggestion of alternatives to read barcodes from usb barcode scanners will be very well appreciated.
Many barcode scanners will hook into a PC as if it were a keyboard, and send through the text string as keyboard input when a barcode is scanned.
That would require no specialist library, as just monitoring keyboard input would be sufficient.
Looking through the specifications of your specific "datalogic gryphon" barcode scanner, it seems like there are some variants and drivers that allow this "Keyboard Interface".
If this is not working for your device, you can use the "COM-serial" or "RS-232" interfaces as input to your PC, and then use a library like pyserial to read in the input of that stream.
TL;DR: This is a driver issue, you can probably get an easy keyboard-like input if you contact the manufacturer of your device. Otherwise PySerial is the library you are probably looking for.
Connecting barcode scanners as keyboards can be problematic (security issues) or unrefined (scanning barcodes into incorrect fields). Here's a Python library that purports to bring barcodes in directly.
https://github.com/vpatron/barcode_scanner_python
I have a question that feels like it should be simple, but my searches haven’t turned up an answer. Hoping someone can help me narrow down keywords or point me to some documentation.
I have a camera connecting to a computer with an Ethernet cable, the output format is MPEG-2 transform stream. I would like to open this in python and run code on it (for the sake of the example - let’s say display it with some text and a frame counter over it), much like I would usually do with a regular usb webcam and opencv.
Is this a simple matter of syntax, or am I going to be running into bigger problems? Also what are the professional terms for what I’m trying to do that would redirect my search to something more productive? (I’m very much a beginner, feel free to assume I am missing basic info)
I'm excited. I'm a long-time lurker here at SO, but I've never posted. Here goes!
I'm trying to develop a device that would connect to a host RPi through (preferably) USB, and would have multiple 3.5mm jack outputs. The goal, ultimately, is to get the device to use a standalone program that, when a button is pressed (keyboard, or other external input), a specific sound (or set of sounds) would go through a single 3.5mm output. Now, I understand that there's going to (most likely) have to be an external box, and I also realize that I'm in above my head, but I'm trying to create this as more of a hobby and as a learning experience.
Basically, the way it would go is that the user would set which inputs triggered which outputs beforehand on the custom software in the RPi. The input would then trigger that ouput then await a new signal. I figure I'm going to need to also build a physical box to house the amount of 3.5mm jacks I want (i figured 3-5.)
So, where do I need to start? I don't need a guide on how to do this, more of a step in the right direction. From what I can discern, there's not anything out there that does this. If there is, please show me and I'll get that instead. I've done a lot of googling on this, and I'm thinking that I'll use Raspbian on the Rpi, and code the software using Python. I know I'll also need to build a driver so that the external box and the RPi can communicate. Lastly, I assume that I'll need some type of circuitry for the external box. That's where it gets hairy to me. I've never dealt in physical I/O except for a bit of modding. Where would I start my search there?
Any help at all is appreciated, and thanks for reading this huge post. Thanks!!!!!!!!!!!!
I have recently been faced with a rather odd task, one result being the necessity for the ability to use DTMF (aka "Touch Tone") tones to control a non-X Linux computer's terminal. The computer has a modem which can be accessed through ALSA, and therefore the sox "rec" program, which is what I am reading the input through. The computer in question is otherwise completely isolated, having no Ethernet or other network interfaces whatsoever. The Goertzel algorithm implementation I am using works very well, as does the eSpeak speech synthesis engine which is the only source of output; this is supposed to work with any Touch Tone phone. It reads back both input (input being octal digits, one ASCII byte at a time)and whatever the dash shell feeds back -- the prompt, the output from commands, etc., using ASCII mnemonics for control characters.
The current method that I am using for interacting with dash and the programs launched through it is the pexpect module. However, I need it to be able to, on demand, read back the entire contents of the line on which the cursor is positioned, and I do not recall pexpect being able to do this (If it is, I cannot tell.). The only other solution that I can think of is to somehow use Python to either control, or act as, the keyboard and console drivers.
Is this, indeed, the only way to go about it (and if so, is it even possible with Python?), or is there another way of having direct access to the contents of the console?
Edit: Through dumb luck, I just recently found that the SVN version of PExpect has pexpect.screen. However, it does not have any way of actually running a program under it. I'll have to keep an eye on its development.
The simple solution is to use the Linux kernel uinput interface. It allows you to insert keypresses and mouse events into the kernel, exactly as if they came from a physical human interface device. This would basically turn your application into a keyboard/mouse.
Since you are working with Python, I recommend you take a look at the python-uinput module.
If you are comfortable with binary I/O in Python, then you can certainly do the same without any libraries; just check out the /usr/include/linux/uinput.h header file for the structures involved (the interface is completely stable), and perhaps some uinput tutorials in C, too.
Note that accessing the /dev/uinput or /dev/input/uinput device (depending on your distribution) normally requires root privileges. I would personally run the Python service as a user and group dedicated to the service, and modify/add a udev rule (check all files under rules.d) to allow read-write access to the uinput device to that group, something like
SUBSYSTEM=="input", ENV{ID_INPUT}=="", IMPORT{builtin}="input_id"
KERNEL=="uinput", MODE="0660", GROUP="the-dedicated-group"
However, if your Python application simply executes programs, you should make it a terminal emulator -- for example, using this. You can do it too without any extra libraries, using the Python pty; the main work is to however simulate a terminal with ANSI escape sequences, so that applications don't get confused, and the existing terminal emulators have such code.
If you want to manipulate the contents of the console, you probably want to use curses. It's well documented here. Look at window.getch() and window.getyx().
I have both Fruityloops and Propellerheads Reason software synths on my Windows PC.
Any way I can get at and script these from either Visual Basic or Python? Or at least send Midi messages to the synths from code?
Update : attempts to use something like a "midi-mapper" (thanks for link MusiGenesis) don't seem to work. I don't think Reason or FL Studio act like standard GM Midi synths.
Update 2 : If you're interested in this question, check out this too.
Both applications support MIDI. It's just that they don't see each other.
In order to send messages via MIDI between applications, you need to install a virtual midi port.
There are several freely available, but this one works: http://www.midiox.com/zip/MidiYokeSetup.msi
You'll get a virtual MIDI output port that you can write to as if it's a normal MIDI device. In Fruity Loops or Rebirth you choose that port as the input. That's all you need to do to connect the programs.
It'll work like this:
Your Application --> Virtual MIDI Port --> FruityLoops
Note: This answer doesn't exactly answer the question you asked but it might achieve the result you want :)
You can author a VST plugin in Java using jVSTWrapper (http://jvstwrapper.sourceforge.net/). If you really wanted to use Python you could use Jython to interface to java and do it that way. Alternatively you could just write the plugin in Java or another scripting language for the JVM like Groovy.
I think both FL Studio and Reason can be configured as the default MIDI playback device. To send MIDI messages to either from VB.NET, you'll need to PInvoke the midiOutOpen, midiOutShortMsg and midiOutClose API calls. Here's a link to code samples:
http://www.answers.com/topic/midioutopen
They're for VB6, but they should be easy to translate to VB.NET.
I know FL Studio can be "driven" from a plugin authored for FL (or a VSTx plugin), but I think these are always written in C or C++.
Edit: I just learned that Windows Vista dropped the MIDI Mapper (which would have made setting up FL or Reason as the default MIDI device simple). Amazing. Here is a link I found with an alternative solution:
http://akkordwechsel.de/15-windows-vista-und-der-midi-mapper/
I just tried it out (it's just a *.CPL file that you double-click to run) and it appears to work (although the GM Synth is the only option available on my laptop, so I'm not sure if it will pick up FL or Reason as choices).
What you need is a VST MIDI scripter / scripting plugin to create a logic of MIDI events that can be sent to any MIDI channel. You would need to set a MIDI channel in FL for the VST instrument/effect you need to tweak its values. Google for it there are some plugins around and please share them back here if you find anything useful :)
You could write a Rewire host. Though, you will have to get a license (the license is free, but your application must be proprietary, so no open source).
Alternatively, you could interface through MIDI messages.
Finally, you could implement a dummy audio device which would route the audio to/from wherever you want or process it in some way.
I imagine all of these would be reasonably difficult. MIDI is probably the easiest of the three (I have no idea how easy or hard the Rewire protocol is to use).
When it comes to Reason, you can do with it to much because of it's closed architecture - you can use VST plugins (or any other type like DirectX ones) - your only option is to use MIDI.
Regarding Fruity Loops, you could write a VST plugin that can take an input from a scripting language (VB, Python or whatever) but in order to write such thing you would have to use Delphi or C++.
Alternatively, you can check out MAX made by Cycling74 - it's something like a IDE for music ;-) - and I'm pretty sure you can use Python with it.
There's an opensource music workstation, called Frinika, and you can script that in Javascript. (Insert / delete notes , change midi effects like pitch wheel etc.) It can import / export regular midi files, so it will work with Fruity loops or whatever else you have.
// Insert New
song.newLane("MyMidiLane", type("Midi"));
lane = song.getLane("MyMidiLane");
part = lane.newPart( time("10.0:000"), time("4.0:000") );
part.insertNote(note("c#3"), time("11.2:000"), time("2:0"), 120 );
part.insertNote(note("f3"), time("11.3:000"), time("1:0"), 100 );
part.insertNote(note("g#3"), time("11.3:000"), time("1:0"), 100 );
part.insertNote(note("b3"), time("11.3:000"), time("0:64"), 100 );
part.removeNote(note("f3"), time("11.3:000"));
part = song.newLane("MyTextLane",
type("Text")).newPart(time("24.0:000"), time("10.0:000"));
part.text = "This is the test text to be inserted.";
part.lane.parts[0].remove(); // remove initially inserted text-part
Another example for reading/changing notes:
lane = song.getLane("MyMidiLane");
// a lane has a fixed instrument assigned
lane.parts[0].notes[0].duration=64
lane.parts[0].notes[1].duration=32
lane.parts[0].notes[1].startTick=120
// Parts are blocks of notes that you can drag around together in the Frinika GUI.
// They're like patterns in trackers.
for (i in lane.parts[0].notes){
println("i: "+i+", n: "+noteName(lane.parts[0].notes[i].note));
println("i: "+i+", dur: "+lane.parts[0].notes[i].duration);
println("i: "+i+", startT: "+lane.parts[0].notes[i].startTick);
}
http://frinika.appspot.com/
It has a Java Webstart launcher as well, so you don't even have to
install.
It used to bundle the Javadoc documentation as well, but for some
reason their latest downloads don't include that. It's a pity, because
that's where the Javascript bindings are documented. So, now you have
to browse the source or build the Javadoc yourself. (It has some built-in examples that are accessible from the scripting window, you should check them out first. My first example is from there.)
Here is the sourcefile where you'll find the Javascript docs:
frinika Javascript doc/source
But there are other options as well. You can check out mingus too, which is a Python library for music theory and midi file handling. It requires Fluidsynth, and the demo apps require GamePython too, so it's a bit more complicated to setup than Frinika.
P.S.:
Frinika has a particular bug: when dragging around neighbouring notes, some might not sound the right length. You can help that by transposing forth and back the consecutive notes (fairly fast in piano roll view), or dragging the part that contains the notes forth and back. Restarting Frinika will also help, but that's the slower way. So this bug won't affect saved files, neither midi export.