MICROSOFT_PRESS_EBOOK_PROGRAMMING_WINDOWS_8_APPS_WITH_HTML_CSS_AND_JAVASCRIPT_PDF

In Scenario 2, the sample always uses the WVGA encoding but allows you to set specific values for
the video dimensions, the frame rate, the audio and video bitrates, audio channels, and audio sampling.
It applies these settings in getCustomProfile (js/custom.js) simply by configuring the profile properties
after the profile is created:
function getCustomProfile() {
if (g_useMp4) {
g_profile = Windows.Media.MediaProperties.MediaEncodingProfile.createMp4(
Windows.Media.MediaProperties.VideoEncodingQuality.wvga);
} else {
g_profile = Windows.Media.MediaProperties.MediaEncodingProfile.createWmv(
Windows.Media.MediaProperties.VideoEncodingQuality.wvga);
}
}
// Pull configuration values from the UI controls
g_profile.audio.bitsPerSample = id("AudioBPS").value;
g_profile.audio.channelCount = id("AudioCC").value;
g_profile.audio.bitrate = id("AudioBR").value;
g_profile.audio.sampleRate = id("AudioSR").value;
g_profile.video.width = id("VideoW").value;
g_profile.video.height = id("VideoH").value;
g_profile.video.bitrate = id("VideoBR").value;
g_profile.video.frameRate.numerator = id("VideoFR").value;
g_profile.video.frameRate.denominator = 1;
And to finish off, Scenario 3 is like Scenario 1, but it lets you set start and end times that are then
saved in the transcoder’s trimStartTime and trimStopTime properties (see js/trim.js):
transcoder = new Windows.Media.Transcoding.MediaTranscoder();
transcoder.trimStartTime = g_start;
transcoder.trimStopTime = g_stop;
Through not shown in the sample, you can apply effects to a transcoding operation by using the
transcoder’s addAudioEffect and addVideoEffect methods.
Custom Decoders/Encoders and Scheme Handlers
Clearly, there are many more audio and video formats in the world than Windows can support in-box,
so an extensibility mechanism is provided in WinRT to allow for custom bytestream objects, custom
media sources, and custom codecs and effects. It’s important to note again that all such extensions are
available only to the app itself and are not available to other apps on the system. Furthermore, Windows
will always prefer in-box components over a custom one, which means don’t bother wasting your time
creating a new mp3 decoder or such since it will never actually be used.
As suggested earlier with custom image formats, this subject will certainly take you into some pretty
vast territory around the entire Windows Media Foundation (WMF) SDK. What’s in WinRT is really just a
wrapper, so knowledge of WMF is essential and not for the faint of heart!
Audio and video extensions are declared in the app manifest where you’ll need to edit the XML
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