Develop Reference

Create Cross-Platform Application (Android, iOS) as an option to open PDF documents

Hello,
I've developed an Android application in Java for creating electronic signatures upon PDF documents. To run the application, the user should choose a PDF document from stored documents and after the Open With picker prompts, the user should choose the developed application and the application starts. In Java I managed to do that by setting an intent-filter (with mimetype set for application/pdf) in the Antroid Manifest file of the project. I want to do the same thing in a Xamarin.Forms cross-platform application. Is there any way to achieve this?

This is possible through official Xamarin.Essentials:
https://learn.microsoft.com/en-us/xamarin/essentials/launcher?context=xamarin%2Fxamarin-forms&tabs=android
This features enables an app to request other apps to open and view a
file. Xamarin.Essentials will automatically detect the file type
(MIME) and request the file to be opened.
Here is a sample of writing text to disk and requesting it be opened:
var fn = "File.txt";
var file = Path.Combine(FileSystem.CacheDirectory, fn);
File.WriteAllText(file, "Hello World");
await Launcher.OpenAsync(new OpenFileRequest
{
File = new ReadOnlyFile(file)
});

How to extract Thumbnail of MP4 Video located in azure storage

I want to extract a thumbnail from an mp4 video hosted in azure storage. My current method in C# uses a NReco NuGet package:
But that is a local file. How do i extract the thumb from an azure storage file.
string mp4inputpath = server.mappath("~/testfolder/myvideo.mp4");
string thumbOutputPath = server.mappath("~/testfolder/mythumb.jpg");
var ffMpeg = new NReco.VideoConverter.FFMpegConverter();
// Get the thumb at the frame 1 second into the video
ffMpeg.GetVideoThumbnail(mp4inputpath, thumbOutputPath, 1);
That works! But i need to use an azure storage file url for mp4inputpath.
I can download the mp4 file from azure storage and save it temporarily into my azure web app. I can do that programatically.
Then extract the thumb, ie,
ffMpeg.GetVideoThumbnail(mp4inputpath, thumbOutputPath, 1);
Then delete the temporary mp4 within my app.
this works but i don't know it is advisable to download mp4 files into my azure web app. I don't know if it will scale. This is the only solution i have, so far.
string mp4Url = #"https://mysorageaccount.blob.core.windows.net/mp4/vacation/summer/dogbarking.mp4";
string thumbOutputPath = server.mappath("~/testfolder/mythumb.jpg");
var ffMpeg = new NReco.VideoConverter.FFMpegConverter();
// Get the thumb at the frame 1 second into the video
ffMpeg.GetVideoThumbnail(mp4Url, thumbOutputPath, 1);
This does not seem to work. No Error, but the thumbOutputPath file is empty.

What you've done is pretty much what you have to do, since you cannot open an object in Azure Storage as you would a local file. So, grabbing the file into a local file or a stream is what you'd need to do.
As far as scaling: that will depend on the size (and number of instances) you're running in your Web App. Just be aware that you should have both your storage account and your Web App in the same region, to reduce latency and avoid egress charges for bandwidth.

Wait for an launched application to stop

We are currently working on a project in UWP where we have to start an external application to modify some documents.
We looked into the Windows.System.Launcher API but it seems that we need more than what it can offer us.
As we launched the application from a file, we use the LaunchFileAsync method, based on the example given by the MSDN :
async void DefaultLaunch()
{
// Path to the file in the app package to launch
string imageFile = #"images\test.png";
var file = await Windows.ApplicationModel.Package.Current.InstalledLocation.GetFileAsync(imageFile);
if (file != null)
{
// Launch the retrieved file
var success = await Windows.System.Launcher.LaunchFileAsync(file);
if (success)
{
// File launched
}
else
{
// File launch failed
}
}
else
{
// Could not find file
}
}
So far, the example suit us well but we also need to be warned when the user is done with the file. The best would be to be able to give the launcher a callback method.
We haven't found anything like that yet in the documentation. Is this even possible ? Do we need to use another solution ?
TL;DR : Is there a solution to open another application from a UWP app and wait for it to return a result object ?

If the external app is also a UWP app then Launcher.LaunchUriForResultsAsync is designed for this. It will launch the target app then wait for the app to call back with the results.
See Launch an app for results for a full walkthrough of how this works.
If the target app isn't a UWP app then you can implement the same thing yourself: both apps declare a protocol. The client launches the server with the server's protocol. When the server's done it notifies the caller by launching the client's protocol.
You might also want to look into App Services which allow a UWP server app to expose a REST-like service to clients on the local system. 

The app process isolation model means you can't do this from a UWP app. As you just want to know when an arbitrary program has finished you could write this in traditional .net/win32 and include that in your UWP app via the desktop bridge.

Audio encoding via IIS mvc4

I am uploading audio file to server normally, now I want to get the mp3 file 196kbps and set to 128kbps.
NAudio.Wave.Mp3FileReader wave = new NAudio.Wave.Mp3FileReader(stream);
Id3.Mp3Stream wave2 = new Id3.Mp3Stream(stream, Id3.Mp3Permissions.ReadWrite);
I can load all information about the mp3 but I cant modify anything about audio quality. Any option/slampe to do that on asp.net?

Read this article about audio converting in .NET
You can all things you can do in .NET in ASP,NET.
http://www.codeproject.com/Articles/501521/How-to-convert-between-most-audio-formats-in-NET

Creating a ASP.NET application converting text to speech

I seek some insight in creating an application that converts text to speech in ASP.NET. From my initial research, it appears that:
MS SAPI requires the client to download an ActiveX component and can support large amounts of text to be converted. Our clients are not willing to install any components on their systems, so this approach may or may not fly.
I do understand with .NET 3.0, we have the System.Speech.Synthesis namespace. Does the conversion take place on the server? If so, how would I serve it to the client?
Our requirements are ability to convert large amount of text, should be scalable and reliable. Which technology is "production ready" capable of serving a large number of requests in a short time interval.
Any thoughts are appreciated.

By default, ASP.Net applications don't run with sufficient permissions to access Speech Synthesis, and attempting to run Larsenal's code will fail with a security error.
I was able to get around this in an app by having a separate WCF service running on the server, as a regular Windows Service. The ASP.Net application then communicated with that service. That service just wrapped Larsenal's code, returning an array of bytes, given a string of text.
Also, one megabyte of text? That's a good-sized novel.
Edit, 11-12-09, answering some comments:
System.Speech can either return an array of bytes, or save to a wav file, which you can then feed to a media player embedded on the user's page. When I built my talking web page, it worked like this:
1) Page.aspx includes an 'embed' tag that puts a Windows Media Player on the page. The source is "PlayText.aspx?Textid=whatever".
2) PlayText.aspx loads the appropriate text, and communicates (via WCF) to the speechreader service, handing it the text to read.
3) The Speechreader service creates a MemoryStream and calls SpeechSynthesiser.SetOutputToWaveStream, and then returns the stream as a single array of bytes. This array is Response.Write()-ed to the client.
Here's the meat of the SpeechReader service:
byte[] ITextReader.SpeakText(string text)
{
using (SpeechSynthesizer s = new SpeechSynthesizer())
{
using (MemoryStream ms = new MemoryStream())
{
s.SetOutputToWaveStream(ms);
s.Speak(text);
return ms.GetBuffer();
}
}
}
I'm pretty sure that on the back end, this returns an enormous XML array-of-bytes, and is horribly inefficient. I just did it as a proof of concept, and so didn't research that. If you intend to use this in production, make sure that it's not internally returning something like this:
<byte>23</byte>
<byte>42</byte>
<byte>117</byte>
...

With the SpeechSynthesizer, you can output to a WAV file. You could then have a secondary process compress or convert to another format if needed. All this could be done on the server and then sent up through the browser.
This CodeProject article is a good introduction to .NET Speech Synthesis.
If you want to see how it performs with a LOT of text.... Add a reference to System.Speech and then use the following as a starting point:
using System;
using System.Speech.Synthesis;
namespace SpeakToMe
{
class Program
{
static void Main(string[] args)
{
SpeechSynthesizer synth = new SpeechSynthesizer();
synth.SetOutputToWaveFile("c:\\test.wav");
synth.Speak("Hello, world.");
synth.SetOutputToDefaultAudioDevice();
Console.ReadLine();
}
}
}
A quick test on a file of 44,700 words (238KB) on my relatively fast machine...
Completed in 55 seconds
Generated a 626 MB WAV file

I searched for "Convert Text Into Speech In Asp.Net" in Google and found a very nice and usefull link:
http://codeprojectdownload.com/asp-net-2/convert-text-into-speech-in-asp-net/#.T0ScXIfXDZE
It may also be useful to you.

I achieved this by using codeBehind to run a javascript function that runs the text-to-speech command:
codeBehind:
Page.ClientScript.RegisterStartupScript(
GetType(),
"anythingHere",
"nameOfFunction();",
true);
javascript:
<script>
function nameOfFunction()
{//start
var msg = new SpeechSynthesisUtterance('READ ME!');
window.speechSynthesis.speak(msg);
}//end
</script>

I wrote an article on this on my blog: http://weblogs.asp.net/ricardoperes/archive/2014/04/08/speech-synthesis-with-asp-net-and-html5.aspx. I used AJAX and Data URIs to send voice data back and forth between the client and the server.