I am porting coding from Objective C to MonoTouch to use an external accessory. It is super basic coding, however when I create The EASession and try to use the InputStream or OutputStream, they are both NULL. I have used it in Objective-C so I know this should not happen.
I am able to repeatedly connect/disconnect the device and detect it. Now I just can't seem to read the data from the device because of this null issue. Below is my coding:
session = new EASession(acc, "com.idtechproducts.reader");
session.OutputStream.Delegate = streamDel; // Crashed saying OutputStream is null
session.OutputStream.Schedule (NSRunLoop.Current , "NSDefaultRunLoopMode");
session.OutputStream.Open ();
You need to list the external accessories you're going to use in your
Info.plist.
There is some documentation on this on apple's site:
http://developer.apple.com/library/ios/#featuredarticles/ExternalAccessoryPT/Introduction/Introduction.html#//apple_ref/doc/uid/TP40009502
Here is a screenshot of how to set this value in Info.plist:
http://screencast.com/t/AYmOWjf8wkL
Related
I'm making a gym management web app that handles sign-ins. Members have a barcode on a tag that they scan when they arrive to the gym.
I've heard that most barcode scanners simply act as a keyboard. This would require the scanning-in page to be open and in the foreground when a barcode is scanned.
If it's just a keyboard, how would I send the barcode scanner input to a single background process running on the computer, and have it ignore by all processes that may be in focus?
You're right that most scanner can support HID in keyboard emulation, but that's just the start.
If you want to have a bit more control over the data you can use a scanners that support the OPOS driver model.
Take a look at Zebra's Windows SDK to have a overview of the things that you can do. It may be a better solution than try to steal the barcode data coming in the OS as a keyboard entry to the foreground app.
Disclaimer: I work for Zebra Technologies
Other Barcode scanner vendor support a similar driver model.
I found an interesting post with a simple solution:
On the form constructor
InitializeComponent():
this.KeyPress += new System.Windows.Forms.KeyPressEventHandler(this.Form1_KeyPress);
Handler & supporting items:
DateTime _lastKeystroke = new DateTime(0);
List<char> _barcode = new List<char>(10);
private void Form1_KeyPress(object sender, KeyPressEventArgs e)
{
// check timing (keystrokes within 100 ms)
TimeSpan elapsed = (DateTime.Now - _lastKeystroke);
if (elapsed.TotalMilliseconds > 100)
_barcode.Clear();
// record keystroke & timestamp
_barcode.Add(e.KeyChar);
_lastKeystroke = DateTime.Now;
// process barcode
if (e.KeyChar == 13 && _barcode.Count > 0) {
string msg = new String(_barcode.ToArray());
MessageBox.Show(msg);
_barcode.Clear();
}
}
Credits: #ltiong_sh
Original post: Here
Use RawInput API (https://www.codeproject.com/Articles/17123/Using-Raw-Input-from-C-to-handle-multiple-keyboard#_Toc156395975) and check device ID for incoming keystrokes. Different devices have different IDs. You can also block keystrokes from scanner from reaching your application and interfering with input fields.
One thing you might want to add is option for user to identity which device is used as a barcode scanner. I did it by asking user to test-scan barcode with scanner on first application startup or in settings.
Works with any barcode scanner which outputs keystrokes.
I have a EmbeddedMediaPlayerComponent and I want to check before playing if the video has audio track.
The getMediaPlayer().getAudioTrackCount() method works fine but only when I play the video and I am inside the public void playing(MediaPlayer mp) event.
I also tryed
getMediaPlayer().prepareMedia("/path/to/media", null);
getMediaPlayer().play();
System.out.println("TRACKS: "+getMediaPlayer().getAudioTrackCount());
But it does not work. it says 0.
I also tryed:
MediaPlayerFactory factory = new MediaPlayerFactory();
HeadlessMediaPlayer p = factory.newHeadlessMediaPlayer();
p.prepareMedia("/path/to/video", null);
p.parseMedia();
System.out.println("TRACKS: "+p.getAudioTrackCount());
But it also says -1. Is there a way I can do that ? or using another technique?
The track count is not metadata, so using parseMedia() here is not going to help.
parseMedia() will work to get e.g. ID3 tag data, title, artist, album, and so on.
The track data is usually not available until after the media has started playing, since it is the particular decoder plugin that knows how many tracks there are. Even then, it is not always available immediately after the media has started playing, sometimes there's an indeterminate delay (and no LibVLC event).
In applications where I need the track information before playing the media, I usually would use something like the native MediaInfo application and parse the output - this has a plain-text out format, or an XML output format and IIRC the newer versions have a JSON output format. The downside is you have to launch a native process to do this, I use CommonsExec for things like this. It's pretty simple and does work even though it's not a pure Java solution, but neither is vlcj!
A slight aside if you did actually want the meta data there is an easier way, just use
this method on the MediaPlayerFactory:
public MediaMeta getMediaMeta(String mediaPath, boolean parse);
This gives you the meta data without having to prepare, play or parse media.
I am trying to capture audio from the mic using the windows core audio APIs
The relevant lines of code are
const CLSID CLSID_MMDeviceEnumerator = __uuidof(MMDeviceEnumerator);
const IID IID_IMMDeviceEnumerator = __uuidof(IMMDeviceEnumerator);
IMMDeviceEnumerator *pEnumerator = NULL;
hr = CoCreateInstance(CLSID_MMDeviceEnumerator,NULL,CLSCTX_ALL,IID_IMMDeviceEnumerator, (void**)&pEnumerator);
hr returns the following value-
0x800401f0 : CoInitialize has not been called.
I have adapted the sample program from the msdn page - Capturing an audio stream
What could be wrong? Also I don't understand what the error means - from the descriptions I got from Google search and all.
I am using Visual studio 2012 express on Win7 Home Pro x64.
Isn't the error message clear enough? You need to call CoInitialize before calling CoCreateInstance (or using COM in any other way).
I was wondering how I can select the output device for audio in directshow. I am able to get available audio output devices in directshow. But how can I make one of these to be audio output device. Its always going for the default audio device. I want to be able to output audio on my choice of device. I have been struggling through google but couldn't find anything useful. All I could get was this link but it doesn't really solve my problem.
Any help will be really helpful for me.
First off, if you're not using DirectShow .NET (DirectShowLib), get that here: It serves as a (very complete) interface between unmanaged DirectShow and C#
What follows is a pretty simple example of how to play an audio file, to the desired audio device
using DirectShowLib;
private IGraphBuilder m_objFilterGraph = null;
private IBasicAudio m_objBasicAudio = null;
private IMediaControl m_objMediaControl = null;
private void playAudioToDevice(string fName, int devIndex)
{
object source = null;
DsDevice[] devices;
devices = DsDevice.GetDevicesOfCat(FilterCategory.AudioRendererCategory);
DsDevice device = (DsDevice)devices[devIndex];
Guid iid = typeof(IBaseFilter).GUID;
device.Mon.BindToObject(null, null, ref iid, out source);
m_objFilterGraph = (IGraphBuilder)new FilterGraph();
m_objFilterGraph.AddFilter((IBaseFilter)source, "Audio Render");
m_objFilterGraph.RenderFile(fName, "");
m_objBasicAudio = m_objFilterGraph as IBasicAudio;
m_objMediaControl = m_objFilterGraph as IMediaControl;
m_objMediaControl.Run();
}
It is up to user to manage audio devices and choose a primary device (such as via Control Panel applet). You can find ways to switch devices programmatically in Windows XP, however in Vista+ it is impossible without interactive user action by design.
See also Larry's answer here: How to change default sound playback device programmatically?
UPDATE: The mentioned above refers to modifying system configuration trying to alter default audio output device. An application is however not limited to default device only. Instead, it can enumerate available devices (see Using the System Device Enumerator + CLSID_AudioRendererCategory) and then create an instance of renderer for specific device with BindToObject call. From there on, it is a regular filter, just bound internally to device of interest.
I am targeting windows machines. I need to get access to the pointer to the byte array describing the individual streaming frames from an attached usb webcam. I saw the playcap directshow sample from the windows sdk, but I dont see how to get to raw data, frankly, I don't understand how the video actually gets to the window. Since I don't really need anything other than the video capture I would prefer not to use opencv.
Visual Studio 2008 c++
Insert the sample grabber filter. Connect the camera source to the sample grabber and then to the null renderer. The sample grabber is a transform, so you need to feed the output somewhere, but if you don't need to render it, the null renderer is a good choice.
You can configure the sample grabber using ISampleGrabber. You can arrange a callback to your app for each frame, giving you either a pointer to the bits themselves, or a pointer to the IMediaSample object which will also give you the metadata.
You need to implement ISampleGrabberCB on your object, and then you need something like this (pseudo code)
IFilterInfoPtr m_pFilterInfo;
ISampleGrabberPtr m_pGrabber;
m_pGrabber = pFilter;
m_pGrabber->SetBufferSamples(false);
m_pGrabber->SetOneShot(false);
// force to 24-bit mode
AM_MEDIA_TYPE mt;
ZeroMemory(&mt, sizeof(mt));
mt.majortype = MEDIATYPE_Video;
mt.subtype = MEDIASUBTYPE_RGB24;
m_pGrabber->SetMediaType(&mt);
m_pGrabber->SetCallback(this, 0);
// SetCallback increments a refcount on ourselves,
// but we own the grabber so this is recursive
/// -- must addref before SetCallback(NULL)
Release();