Reputation: 681
Can someone provide me the sample code or example for reading each frame of Camera video using PreviewCallback interface?
I want to get the frame without using surface as I want frame of the camera video first without displaying on the screen and then I can pass that frame to the CCLayer of cocos2dx.
Upvotes: 0
Views: 612
Reputation: 12656
This is a slow process and cannot process every frame of data delivered to the preview callback. It should only be used if your requirements for a live preview application make it impossible to display video from the camera or video from the camera with a stencil type overlay, and your display can tolerate only a few frames per second with some latency.
Some important steps:
onPreviewFrame()
. byte[]
array data sent to onPreviewFrame()
is in YCbCr_422_SP
format. No other formats are available, even if you attempt to set
them. The data is described here: http://groups.google.com/group/android-developers/msg/d3b29d3ddc8abf9b onPreviewFrame()
. There isn't enough
time - you will hose the camera if you try to hold up the system in
that function for so long. Copy the data to your own buffer and
decode in a separate Thread
.Thread
is processing any particular frame. Wait until the Thread
is finished before
using the data from the next available frame.Decode the YUV Preview Data:
// decode Y, U, and V values on the YUV 420 buffer
// described as YCbCr_422_SP by Android - David Manpearl
public static void decodeYUV(int[] out, byte[] fg, int width, int
height) throws NullPointerException, IllegalArgumentException {
final int sz = width * height;
if(out == null) throw new NullPointerException("buffer 'out' is null");
if(out.length < sz) throw new IllegalArgumentException("buffer 'out' size " + out.length + " < minimum " + sz);
if(fg == null) throw new NullPointerException("buffer 'fg' is null");
if(fg.length < sz) throw new IllegalArgumentException("buffer 'fg' size " + fg.length + " < minimum " + sz * 3/ 2);
int i, j;
int Y, Cr = 0, Cb = 0;
for(j = 0; j < height; j++) {
int pixPtr = j * width;
final int jDiv2 = j >> 1;
for(i = 0; i < width; i++) {
Y = fg[pixPtr]; if(Y < 0) Y += 255;
if((i & 0x1) != 1) {
final int cOff = sz + jDiv2 * width + (i >> 1) * 2;
Cb = fg[cOff];
if(Cb < 0) Cb += 127; else Cb -= 128;
Cr = fg[cOff + 1];
if(Cr < 0) Cr += 127; else Cr -= 128;
}
int R = Y + Cr + (Cr >> 2) + (Cr >> 3) + (Cr >> 5);
if(R < 0) R = 0; else if(R > 255) R = 255;
int G = Y - (Cb >> 2) + (Cb >> 4) + (Cb >> 5) - (Cr >> 1) + (Cr >> 3) + (Cr >> 4) + (Cr >> 5);
if(G < 0) G = 0; else if(G > 255) G = 255;
int B = Y + Cb + (Cb >> 1) + (Cb >> 2) + (Cb >> 6);
if(B < 0) B = 0; else if(B > 255) B = 255;
out[pixPtr++] = 0xff000000 + (B << 16) + (G << 8) + R;
}
}
}
Convert byte[]
Array to Bitmap
:
Bitmap bitmap = BitmapFactory.decodeByteArray(out , 0, out.length);
Upvotes: 1