Tag Archives: development

Fixing the Mango Microphone issue – part 2

In the first part of this short series I have demonstrated that Mango has somewhat broken XNA Microphone object, at least when it is used in Silverlight. Even the standard Microsoft’s own Silverlight Microphone Sample generates a broken sound record with some data missing, if you change the buffer length from default 500 ms to 100 ms.

Look at the sound sample recorded with 500 ms buffer on Mango, or with 100 ms buffer on NoDo:

Debug Wave recorded by NoDo 7.0 Emulator in SDK 7.1

Joined 100 ms NoDo or 500 ms Mango Debug Wave records on both phone and emulator look similar to this graph (click on it for a bigger picture).

The same sound sample recorded with 100 ms buffer on Mango:

Debug Wave recorded by Mango 7.1 Samsung Omnia 7 with 100 ms buffer

Joined 100 ms Mango Debug Wave records on both phone and emulator look similar to this one. The wider (louder) marker waves are unevenly spaced, so some data is missing.

My next step was to measure the real rhytm of the buffers generated by the Microphone. Note that you cannot use System.DateTime.Now property, because of its ca 50 ms resolution. Instead, we will use System.Diagnostics.Stopwatch object, which provides better than 1 ms accuracy.

In theory, the Microphone should fire the BufferReady event every 100 ms. But the reality is quite different.

This is the list of the intervals – measured in milliseconds – between the subsequent 100 ms BufferReady events in the (emulated) NoDo:


As you can see, there is a regular pattern of the three 100+, 50+ and 150+ ms intervals, with some swaps. Ten intervals usually make ca 1011 ms. The length of the buffer is always 3200 B and the buffer contains 1600 x 16bit samples, which make 100 ms of sound. Buffers are perfectly connected to each other and no sample is missing or superfluous. (I haven’t yet cracked the interesting question where are going these surplus 11 milliseconds.)

Let’s switch to Mango:


This is recorded on Samsung Omnia 7. The emulator produces different values, but with a similar pattern: This time there are four, not three typical lengths – ca 100, ca 140, ca 70, ca 35. The sum of ten intervals is usually ca 1005 ms now, so it’s better, but the output data is incomplete. It seems that the intervals longer than 100 ms overflow the buffer.

The Microphone object is part of Microsoft.Xna.Framework.Audio namespace. It is dependent on the XNA Framework game loop. You can use it in the Silverlight Windows Phone project, but you have to simulate the game loop with a code like this:

DispatcherTimer dt = new DispatcherTimer();
dt.Interval = TimeSpan.FromMilliseconds(33);
dt.Tick += new EventHandler(dt_Tick);

void dt_Tick(object sender, EventArgs e)
     try { FrameworkDispatcher.Update(); }
     catch { }

33 milliseconds is a timer interval used in the Microsoft’s Silverlight Microphone Sample. I have used the same value, but my next step was to experiment with different timer intervals. Indeed, the resulting Microphone tick lengths were somewhat different, but there was always some data missing, overflowing the buffer – the fundamental issue hasn’t disappeared.

Perhaps you already suspect the solution: We just need a bigger buffer! So, let’s record it with a 6400 B buffer.

Debug Wave recorded with a 6.400 B buffer

Folks, this looks promising! At first look, when we erase the gaps, and join the signal segments, the resulting record may be perfect… Let’s try it in Excel…

6400 B buffer segments compacted in Excel

Oops! 😦 What could have gone wrong???

Why are some segments too long, but no segment is too short? These 35 ms segments should have been short, I guess? Wait! Do I clear the buffer every time? No, it wasn’t necessary in NoDo, because the buffer was always filled up to its fullness in every Microphone tick. In Mango, the Microphone buffer must be cleared before every BufferReady event. 😦 Let’s go on!

Cleared, recorded and compacted 6400 B buffers.


So the winning process is:

  1. Allocate bigger than nominal buffers.
  2. Clear them.
  3. Fill them.
  4. Join only the filled parts of them.

This seems weird. The Microphone object has GetSampleSizeInBytes method. So we should just invoke this method after (or before) every tick and it should return the actual buffer size… but no, it doesn’t work this way. I have played with it for some time, but it always returns just the BufferDuration x 3200 value. It doesn’t reflect the real tick record size, just its ideal size, which is always matched in NoDo, but never in Mango…

The issue with the XNA Microphone object in Mango with 100 ms buffer is that the real buffer length is variable and there is no working API to get its length!

The good news is that no data is really lost. We just don’t know we actual size of the one tick record, so we have to figure it with some workaround. The way to go is to count zeros from the end of the buffer backwards. It may be slightly wrong in some cases, when the sound samples are actually zero at the end of the partial records, for example when the wave crosses the X axis and has exactly zero value at the end of the record. But these cases are quite rare and we can neglect them – at least if we are building a tuner.

In the next and the last part of this mini-series I will publish the source code of the Carousel object, which uses the above described methods to deliver solid data from the capricious Mango Microphone. The living proof of its reliability is my app Accurate Tuner Pro, probably the best pitch tuner for Windows Phone.


What should Microsoft do now? Change GetSampleSizeInBytes of the Microphone object to return the actual size of the just recorded buffer.

Let’s hope it’s fixed in Tango. But still, Tango rollout is going to take some time, so the Carousel object may help you.

To be continued.


Filed under WP developement

Fixing the Mango Microphone issue – part 1

Last september, when Windows Phone 7.5 Mango update was released, it broked my Accurate Tuner Beta. I’ve analysed the issue and was able to release the update that fixed it.

The two videos below illustrate the situation. First the trouble (Mango is installed on the phone, while the emulator still uses NoDo and works properly):

Then the solution:

I promised to explain it in detail back then, but I lacked the time to do it. Now, when I have sent Accurate Tuner Pro to the Marketplace certification, I can fulfill my promise and write a short series about this issue.

Perhaps it is not so important now, because new Tango update is behind the corner and may fix it. In the last part of this series (3rd or 4th) I will publish the source code for the Carousel object, which is used by Accurate Tuner for harvesting solid sound data from somewhat broken Mango microphone.

To map the problem I have created a simple tone generator. It produces a 500 Hz wave (B4 + 21 cents) with a specific shape: “Normal” wave has the amplitude of  5.000, while every 10th wave has the amplitude of 15.000. The resulting “hedge clipper” shape makes a growling sound and looks like this:

Source Debug Wave 500 Hz with 50 Hz markers

Source Debug Wave 500 Hz with 50 Hz markers

Click on it for a bigger picture.

Wave parameters:

  • Sampling rate: 16 000 Hz – the default sampling rate of Windows Phone OS 7.0 and 7.1
  • Base frequency: 500 Hz, wave length 32 samples
  • Frequency of the markers: 50 Hz, wave length 320 samples

Tone Generator source code:

/// <summary>
/// Creates the DEBUG Wave with the debug parameters
/// </summary>
public void CreateDebugWave()
    _samplingRate = 16000;
    _frequency = 500;
    double _normalAmplitude = _amplitude = 5000;
    double markerWaveAmplitude = 15000;
    int markerWaveStep = 10;

    int waveLength = (int)(_samplingRate / _frequency);
    int markerSampleStep = markerWaveStep * waveLength;

    double doubleSample = 0;
    Int16 intSample = 0;
    byte[] byteSample = new byte[2];
    double b = (Math.PI * 2) * _frequency / _samplingRate;

    int j = 0;

    // The wave buffer is one second long
    // This works for whole number of waves (= integer 
    // frequencies) only. 500 Hz or 440 Hz is OK, while
    // 261.63 Hz will make a snapping sound every second.
    for (int i = 0; i < _samplingRate; i++)
        // Marker wave creation
        // This is simple and clear, but not very efficient.
        // It doesn't matter here.
        if (i % markerSampleStep == 0)
            _amplitude = markerWaveAmplitude;
            if (i % markerSampleStep == waveLength)
                _amplitude = _normalAmplitude;

        doubleSample = Math.Sin(i * b) * _amplitude;
        intSample = (Int16)Math.Round(doubleSample);
        byteSample = BitConverter.GetBytes(intSample);

        _buffer[j] = byteSample[0];
        _buffer[j + 1] = byteSample[1];

        // DEBUG For debug visualization purposes only
        _bufferInt16[i] = intSample;

        j += 2;

/// <summary> 
/// Creates and plays the wave.
/// </summary> 
public void Start()
     // DEBUG 

    SoundEffect sound = new SoundEffect(_buffer,
                        _samplingRate, AudioChannels.Mono);

    if (_isPlaying)
        _soundInstance = null;

    _soundInstance = sound.CreateInstance();
    _soundInstance.IsLooped = true;
    _soundInstance.Volume = _volume;

    _isPlaying = true;

/// <summary>
/// Stops playing the wave.
/// </summary>
public void Stop()
    if (!_isPlaying)

    _isPlaying = false;

By the way, the more universal version of this tone generator is included in Accurate Tuner Pro.

Now the interesting part begins: To avoid any mistake in my code I’ve used the standard Silverlight Microphone Sample provided by Microsoft. It uses 500 ms long sound buffer by default. This is the record it produces on NoDo (recorded in the 7.0 Emulator of the 7.1 SDK):

Debug Wave recorded by NoDo 7.0 Emulator in SDK 7.1

Debug Wave recorded by NoDo 7.0 Emulator in SDK 7.1

I’ve carefully reviewed much longer part of the record and found no irregularities. This data is solid and can be safely used by Accurate Tuner for two purposes:

  • Wave vizualization, which is phase-normalized for the stroboscopic efect usable for fine tuning.
  • Fast Fourier Transformation algorithm, which analyses component frequencies for rough tuning.

Next, let’s run it on Mango:

Debug Wave recorded by Mango 7.1 Samsung Omnia 7

Debug Wave recorded by Mango 7.1 Samsung Omnia 7 with 500 ms buffer

The growing amplitude is probably caused by the automatically adjusting microphone sensitivity of the phone and is not interesting for us now, it reaches some maximum amplitude and then stays constant. Another thing is more important – I haven’t found anything wrong with this signal too.

Is this the way Accurate Tuner records sound? Almost. 500 ms sound buffer is good enough for most recording purposes, but it is too long for tuners or sound visualizations, because you need fast response in these cases. The shortest buffer length allowed by WP 7.0 and 7.1 is 100 ms and Accurate Tuner uses this buffer length.

So let’s change the buffer length to 100 ms. The picture is wider now, so click on it to maximize it:

Debug Wave recorded by Mango 7.1 Samsung Omnia 7 with 100 ms buffer

Debug Wave recorded by Mango 7.1 Samsung Omnia 7 with 100 ms buffer

Folks, this is clearly wrong!

Apparently, some sound data is lost!

This explains everything: While common sound visualizations used for estetic purposes only will still look as usual, a stroboscopic animation will be inevitably completely broken. FFT will provide more interesting and confusing results, as there are still big portions of correct waves here, but these portions are phase-shifted. The final results will be unstable and very inaccurate, but not completely wrong.

Which is exactly the behavior of the original Accurate Tuner Beta algorithms.

(I’m skipping the chart of the NoDo 100 ms buffer, but believe me the record is perfect and looks just exactly as the chart with the 500 ms buffer. I would also point out that the described issue is present in the WP 7.1 Emulator too, so it isn’t specific for Samsung phones.)

What to do with it??? FFT will work correctly, if only “safe part” of the buffer is used, for example 50 ms. But it will be extremely inaccurate. In fact, even 100 ms is not enough and several buffers must be joined for the analysis to be meaningful. Or I can change the buffer size to 500 ms, but the FTT results would be very delayed in such case and almost unusable. And the wave visualization delayed by 0.5 s will be just comical.

We will see next time.

To be continued.


Filed under WP developement

Accurate Tuner finally works on Mango

I’ve docummented the issues my Accurate Tuner Beta 1.0.0. has with Mango. Put simply, it does not work at all. After quite a lot of hours, I’ve finally managed to repair it!

Yes, it was more demanding than I expected, but all’s well that ends well. After some final testing I will publish the update, so it will be available in the marketplace in a few days. Also, I will publish my findings about the changed Microphone object behaviour in Mango on this blog.

Let’s comment on the video:

  • Notice the Middle C on the Yamaha keyboard is marked as C3, while the tuner shows C4. It is correct – it really is C4 in the scientific notation, used by the Accurate Tuner (261.64 Hz).
  • My left thumb is shaking… no, I’m not that old or terrified, just a little cold. 🙂
  • The fundamental frequency detection is not perfect. Different tone letters or octaves are flashing at times – this is typical for this hard-to-tune guitar with nylon strings I used for this video. Fortunatelly, it’s better with other instruments, including steel-string guitars. In fact, all these tones are harmonics of the base frequency, so do not really matter. All harmonics are in tune at the same time, so you can safely ignore letters and concentrate just on the needle and/or the wave.
  • When you get accustomed to it (and use steel strings 😉 ), you can tune your instrument extremely fast using the wave only.
  • Accurate Tuner design is not Metro and not even beautiful, I know. But it works! Don’t take it for granted, smartphone tuners in general rather do not work well. 😉

1 Comment

Filed under My Apps

VIDEO: Mango vs. NoDo – A Developer’s Trouble (update)

This is my Accurate Tuner Beta for Windows Phone.

Top: NoDo OS version (WP 7.0 – emulator from SDK 7.0, spring 2011 update)

Bottom: Mango (WP 7.1/7.5 RTM, Samsung Omnia 7)

Select 720p.

When in tune, the Wave above the Needle must stand still.

This beta has better than 0.1 Hz accuracy on NoDo, but doesn’t work at all on Mango. Microsoft has changed the Microphone XNA object behavior. The FFT part (Needle) of the Tuner is less accurate and unstable now, results are completely wrong for lower frequencies. The strobo part doesn’t work at all. And the sound wave has very different shape, it seems to be flipped on both axes…

The app had average rating of 4.88 in the Marketplace before Mango. It will go down fast now, of course. It will take at last a week before the update will be published. I should have test it on Mango before the Mango public release, I know. 😉 But I honestly hadn’t expected this kind of change… I’m trying to figure these changes in the XNA sound processing and to fix it ASAP, but it doesn’t seem to be trivial at first. Does anybody know what has exactly changed with Microphone, XNA events dispatching in Silverlight etc. in Mango?



Status update

I hope I’ve already localized the issue – and yes, there is a real change of the Microphone behavior, although it probably still is in accordance with the documentation.

Unfortunately, it’ll take some work to adapt my tuner to that change, but it should be possible. I plan to describe it in my blog later this week.


Filed under My Apps

Nokia / TabCo will release Windows 8 tablet tomorrow (just dreaming)

I guess you have already seen this page: http://www.whoistabco.com/

If not, it may be the right time to see some of their teaser videos. For example that first one, made during Apple WWDC 2011, with the help of skytypers

TabCo is (probably) a virtual company preparing a big media event for tomorrow – Monday, August 15 at 9 a.m. PDT (18:00 CET) – so less than 24 hours from now. They say they are going to launch a new tablet, that will be… er… different. They have said or shown very little so far, but let’s recap these scarce fragments.

  • Avaliable for order in USA in August, in some European countries in September
  • 400 – 500 USD
  • 16:9 screen aspect ratio
  • USB, Bluetooth, SD card slot, WiFi and 3G (no 4G)
  • Build quality comparable to Apple or Nokia
  • Innovative GUI is predictive and takes inspiration from spheres and Rubik cube
  • Will be distributed with a set of apps from the beginning
  • There probably aren’t heaps of native software yet, but Angry Birds and office apps are available
  • Development SDK will be available after the launch

Other observations:

  • They have mentioned Apple or iPad many times, almost always in positive light
  • They have mentioned Google or Android many times, almost always in negative light
  • Microsoft and Nokia were mentioned rarely, usually in positive context

What could TabCo be:

  • Amazon tablet
  • Some startup full of energy and borrowed money
  • ELSE Ltd.
  • Acer Iconia 2
  • Xoom 2, TouchPad 2, Playbook 2 or Galaxy Tab II
  • New Tabasco flavour
  • Well-funded joke
  • Huawei UFO Tablet with Android 2.x much improved by NonSense UI layer
  • Apple iPad HD
  • Nokia (or Intel) MeeGo / Maemo tablet
  • Nokia Windows 8 tablet

The last option is undoubtedly the most interesting one. Let’s dream about it from a developer’s perspective for a while… This would mean that there will be no big revelation at BUILD in September, exactly one month from now. On the contrary, SDK will be available tomorrow and everybody will download it immediately and will frantically play with it for the next few weeks. Many developers will take their own Windows 8 tablets to the BUILD in fact. Everything will be inside out this time…

Although so blatantly betrayed by Microsoft, most developers will be jumping for joy and consider their dreams fulfilled. This new attack of Metro UI will help Windows Phone sales too…

Why this won’t happen

  • We all know Windows 8 is scheduled for 2012. It’s in some unimportant Milestone phase now.
  • Microsoft always gives things to developers first and then – 6-12 months later – the best customers may get something too
  • There are leaked Windows 8 builds with no traces of a tablet interface and these other cool things
  • The Windows 8 UI revelation event showed no spherical interface elements
  • Interface hints in the above video are different – for example that circular context menu hasn’t been shown, video controls were different etc
  • The lack of software for the new platform. Even old Windows software will not work, because this tablet is almost for sure built on the ARM platform.
  • Mary Jo Foley and Paul Thurrott haven’t seen it coming
  • Microsoft is never so fast
  • Microsoft is never so cool (except for that XBox 360 R2D2 Star Wars edition, of course). While some other companies are habitually cool, Microsoft is habitually cold.

Top Secret Microsoft’s Corporate Exchange leak:

Steven Sinofsky: We should develop Windows 8 in a stealth mode and in just two years. That would surprise everybody and make the Wow effect we so desperately need. That would be cool!


XBox 360 Star Wars Limited Edition

XBox 360 Star Wars Limited Edition Kinect bundle is the coolest Microsoft product ever (for sure 😉 )

Why this may happen after all

  • What we have learned about Windows 8 in June was a total surprise to everybody. So Microsoft is able to hide things if it wants (and Sinofsky is in charge). It’s quite probable it wasn’t the final version of UI.
  • That infamous Microsoft silence about the Windows 8 development platform is just insane. It simply makes no sense to hide things just from developers! On the contrary, it sometimes makes sense to hide things from the general public. But a developer conference is not the ideal place for revealing things to the general public! The conclusion? Some revelation is planned before the BUILD.
  • There were hints about Windows development taking just two years, about Windows 8 tablets coming this fall, about Win division defeating Dev division, about Microsoft selecting just a few hardware partners for the first W8 tablets, about Nokia working on a well-thought tablet etc.
  • Nokia – Microsoft pact makes much more sense from a Nokia viewpoint if this is in cards.
  • Software is important. But Microsoft may provide Office, old Windows software written in .NET may work even on ARM, and Windows Phone emulator may provide some not so optimized, but working software. This plan worked for Apple after all.
  • Mary Jo Foley and Paul Thurrott haven’t seen it coming 😉
  • This may just work


Nokia Sea Ray possible virtual buttons

Windows 8 tablet with the Windows Phone emulator. Oh wait!

The Kinks, You really got me:


Filed under Windows 8

Windows Phone Marketplace opens in 19 new countries: Not yet

Great news from Microsoft are coming these days:

Geographic expansion: A large part of your success in Marketplace hinges  on your app’s discoverability and reach. I’m excited to announce a number of new  consumer and developer markets to help get your app in front of more people.

  • 19 new consumer markets. Starting today developers can publish their  apps to consumers in 19 new countries, in addition to the 16 that Marketplace already supports. The 19 new markets include Brazil, Chile, Colombia, Czech Republic, Denmark, Finland, Greece, Hungary, India, Japan, Netherlands, Norway, Poland, Portugal, Russia, South Africa, South Korea, Sweden and Taiwan.
  • 7 new developer markets: Also starting today developers from 7 new markets (Welcome!) can register in App Hub and submit apps. The 7 new developer markets enabled include: Chile, Colombia, Czech Republic, Hungary, Israel, South Africa and South Korea.
  • In a couple of months (early fall 2011), developers will also be able to register from China. We will also expand the registration support already available in India.

But what does this mean in reality? As a developer, I am able to publish my WP apps in 19 new countries now, but are people in these countries able to buy them?

I cannot change my WP device locale now, because it requires a reset to the factory state. But let’s try something much simpler – to change Zune PC client behavior. When you change the locale of your Windows 7, the Zune opens with locally available features. To be able to browse WP7 marketplace, I have my PC set to the UK locale. Let’s look at the Zune menu now:

Zune July 21st 2011, UK locale

Zune July 21st 2011, UK locale

Switching to the CZ locale…

Zune July 21st 2011, UK locale

Zune July 21st 2011, UK locale

So, that’s it. We are not there yet, it’s not possible to buy or even browse neither paid nor free apps in the Windows Phone marketplace on a correctly set PC in Czech Republic. Perhaps you may do it from a correctly set phone, but I doubt it. If any of my readers is able to reset his or her phone now and try a Live account from any of the above mentioned countries, please let me know.

The Beatles, Wait:


Filed under Windows Phone Marketplace

Windows Phone App Hub updated with new features and new countries

As I predicted on Sunday, App Hub was updated. Now it seems that new countries were added:

New Windows Phon App Hub Registration

I didn’t complete the registration yet, so I can’t confirm there is no remaining obstacle for Czech developers, but I don’t expect it.

There are other improvements too, as many devs report. Just an incomplete list for now:

  • New private beta Marketplace – you can distribute your app to max. 100 selected testers and it will work for 90 days. This way the app probably won’t go through the certification process.
  • You can edit some app details (category, artwork) without submitting update
  • Updated layout
  • New crash reports
  • Export of download/purchase details
  • Updated App Hub tems (no details known yet)

Leave a comment

Filed under Windows Phone Marketplace

Developers from Czech Republic and other countries to get Windows Phone Marketplace access tomorrow! (hopefully)

At Prague Mango Event in June this year, Ondrej Strba from Microsoft said that Czech developers will get official access to the Windows Phone Marketplace in the second half of July.

Mango Event Prague in June 2011.

Picture from the Mango Event in Prague in June 2011. Notice the new square Windows Phone logo.

At MIX 2011, the attendees were told there will be a new version of the AppHub this summer.

And this notice was posted on the Microsoft App Hub (the gate to the Windows Phone and XBox Marketplace for developers) on the last Friday:

App Hub down July 18 for service upgrades


Pardon our dust. App Hub will be down for service upgrades for most of the day starting around 10 a.m. PST on Monday, July 18. During this period, developers will be unable to register, to access their Windows Phone developer accounts, or to use the forums.

We appreciate your patience.

So I bet the safe conclusion is that the Marketplace Access for developers from Czech Republic and other new countries is finally coming!

As I reported before, this should be the list of the new countries now eligible for the application submitting:

  • Chile
  • China
  • Colombia
  • Czech Republic
  • Hungary
  • India
  • South Africa
  • South Korea

Sure it’s not a long list and I especially regret Slovakia is missing. However, it is still a pretty good reason for celebration for us!

And let’s hope other AppHub improvements are coming too. For example – the Marketplace can be opened for buyers from new countries. I rather doubt it, because it seems Microsoft waits for new languages to be implemented in Mango before it. Or the submission of the Mango-compatible app could be newly supported. Again, I don’t see this coming, because the Mango developer tools are still in beta and I expect Microsoft to require the final version to be used for the published apps. But on the other hand, just one big Marketplace update this summer would make sense too. Any improvement would be welcomed.

Update under progress


AppHub update under progress

New features? XNA? Maybe my bet wasn’t so safe… 🙂

1 Comment

Filed under Windows Phone Marketplace