c# - Access preview frame from MediaCapture -

i grab preview frames displayed inside captureelement xaml element. source of captureelement set mediacapture object , use startpreview() method start displaying camera. access frames being shown without saving them img or video file. goal capture 10 fps preview , send each frame class accepts byte[].

i tried using capturephototostoragefileasync method not feasible option not want take 10 actual images / second. not want use screencapture stores captured video file. ideally not want store media files temporarily on phone. after looking @ msdn mediacapture, noticed there's method called getpreviewframeasync() method not exist inside windows phone 8.1. stumbled on example not understand how works.

any suggestions on how approach appreciated.

there sample on microsoft github page relevant, although target windows 10. may interested in migrating project functionality.

getpreviewframe: sample capture preview frames opposed full-blown photos. once has preview frame, can edit pixels on it.

here relevant part:

private async task getpreviewframeassoftwarebitmapasync() {     // information preview     var previewproperties = _mediacapture.videodevicecontroller.getmediastreamproperties(mediastreamtype.videopreview) videoencodingproperties;      // create video frame request softwarebitmap preview frame     var videoframe = new videoframe(bitmappixelformat.bgra8, (int)previewproperties.width, (int)previewproperties.height);      // capture preview frame     using (var currentframe = await _mediacapture.getpreviewframeasync(videoframe))     {         // collect resulting frame         softwarebitmap previewframe = currentframe.softwarebitmap;          // add simple green filter effect softwarebitmap         editpixels(previewframe);     } }  private unsafe void editpixels(softwarebitmap bitmap) {     // effect hard-coded operate on bgra8 format     if (bitmap.bitmappixelformat == bitmappixelformat.bgra8)     {         // in bgra8 format, each pixel defined 4 bytes         const int bytes_per_pixel = 4;          using (var buffer = bitmap.lockbuffer(bitmapbufferaccessmode.readwrite))         using (var reference = buffer.createreference())         {             // pointer pixel buffer             byte* data;             uint capacity;             ((imemorybufferbyteaccess)reference).getbuffer(out data, out capacity);              // information bitmapbuffer             var desc = buffer.getplanedescription(0);              // iterate on pixels             (uint row = 0; row < desc.height; row++)             {                 (uint col = 0; col < desc.width; col++)                 {                     // index of current pixel in buffer (defined next 4 bytes, bgra8)                     var currpixel = desc.startindex + desc.stride * row + bytes_per_pixel * col;                      // read current pixel information b,g,r channels (leave out alpha channel)                     var b = data[currpixel + 0]; // blue                     var g = data[currpixel + 1]; // green                     var r = data[currpixel + 2]; // red                      // boost green channel, leave other 2 untouched                     data[currpixel + 0] = b;                     data[currpixel + 1] = (byte)math.min(g + 80, 255);                     data[currpixel + 2] = r;                 }             }         }     } } 

and declare outside class:

[comimport] [guid("5b0d3235-4dba-4d44-865e-8f1d0e4fd04d")] [interfacetype(cominterfacetype.interfaceisiunknown)] unsafe interface imemorybufferbyteaccess {     void getbuffer(out byte* buffer, out uint capacity); } 

and of course, project have allow unsafe code of work.

have closer @ sample see how details. or, have walkthrough, can watch camera session recent //build/ conference, includes little bit of walkthrough through camera samples.