Getting frames from Video Image in Android
Solution 1
In API 17+, you can do conversion to RGBA888 from NV21 with the 'ScriptIntrinsicYuvToRGB' RenderScript. This allows you to easily process preview frames without manually encoding/decoding frames:
@Override
public void onPreviewFrame(byte[] data, Camera camera) {
Bitmap bitmap = Bitmap.createBitmap(r.width(), r.height(), Bitmap.Config.ARGB_8888);
Allocation bmData = renderScriptNV21ToRGBA888(
mContext,
r.width(),
r.height(),
data);
bmData.copyTo(bitmap);
}
public Allocation renderScriptNV21ToRGBA888(Context context, int width, int height, byte[] nv21) {
RenderScript rs = RenderScript.create(context);
ScriptIntrinsicYuvToRGB yuvToRgbIntrinsic = ScriptIntrinsicYuvToRGB.create(rs, Element.U8_4(rs));
Type.Builder yuvType = new Type.Builder(rs, Element.U8(rs)).setX(nv21.length);
Allocation in = Allocation.createTyped(rs, yuvType.create(), Allocation.USAGE_SCRIPT);
Type.Builder rgbaType = new Type.Builder(rs, Element.RGBA_8888(rs)).setX(width).setY(height);
Allocation out = Allocation.createTyped(rs, rgbaType.create(), Allocation.USAGE_SCRIPT);
in.copyFrom(nv21);
yuvToRgbIntrinsic.setInput(in);
yuvToRgbIntrinsic.forEach(out);
return out;
}
Solution 2
Ok what we ended up doing is using the onPreviewFrame method and decoding the data in a seperate Thread using a method which can be found in the android help group.
decodeYUV(argb8888, data, camSize.width, camSize.height);
Bitmap bitmap = Bitmap.createBitmap(argb8888, camSize.width,
camSize.height, Config.ARGB_8888);
...
// decode Y, U, and V values on the YUV 420 buffer described as YCbCr_422_SP by Android
// David Manpearl 081201
public void decodeYUV(int[] out, byte[] fg, int width, int height)
throws NullPointerException, IllegalArgumentException {
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;
}
}
}
Solution 3
I actually tried the code given the previous answer found that the Colorvalues are not exact. I checked it by taking both the preview and the camera.takePicture which directly returns a JPEG array. And the colors were very different. After a little bit more searching I found another example to convert the PreviewImage from YCrCb to RGB:
static public void decodeYUV420SP(int[] rgb, byte[] yuv420sp, int width, int height) {
final int frameSize = width * height;
for (int j = 0, yp = 0; j < height; j++) {
int uvp = frameSize + (j >> 1) * width, u = 0, v = 0;
for (int i = 0; i < width; i++, yp++) {
int y = (0xff & ((int) yuv420sp[yp])) - 16;
if (y < 0) y = 0;
if ((i & 1) == 0) {
v = (0xff & yuv420sp[uvp++]) - 128;
u = (0xff & yuv420sp[uvp++]) - 128;
}
int y1192 = 1192 * y;
int r = (y1192 + 1634 * v);
int g = (y1192 - 833 * v - 400 * u);
int b = (y1192 + 2066 * u);
if (r < 0) r = 0; else if (r > 262143) r = 262143;
if (g < 0) g = 0; else if (g > 262143) g = 262143;
if (b < 0) b = 0; else if (b > 262143) b = 262143;
rgb[yp] = 0xff000000 | ((r << 6) & 0xff0000) | ((g >> 2) & 0xff00) | ((b >> 10) & 0xff);
}
}
}
The color values given by this and the takePicture() exactly match. I thought I should post it here. This is where I got this code from. Hope this helps.
Solution 4
Tim's RenderScript solution is great. Two comments here though:
- Create and reuse
RenderScript rs
, andAllocation in, out
. Creating them every frame will hurt the performance. - RenderScript support library can help you back support to Android 2.3.
Comments
-
Alexander Stolz almost 4 years
I've implemented a simple application which shows the camera picture on the screen. What I like to do now is grab a single frame and process it as bitmap. From what I could find out to this point it is not an easy thing to do.
I've tried using the onPreviewFrame method with which you get the current frame as a byte array and tried to decode it with the BitmapFactory class but it returns null. The format of the frame is a headerless YUV which could be translated to bitmap but it takes too long on a phone. Also I've read that the onPreviewFrame method has contraints on the runtime, if it takes too long the application could crash.
So what is the right way to do this?
-
Brian D about 13 yearsHey Alexander, are you doing any other processing or voodoo magic in the background? I've tried this and end up with an image like this: dl.dropbox.com/u/6620976/image.jpg. Any insight is appreciated.
-
Brian D about 13 yearsNevermind! I just needed to define my surface's width and height and it all works great. Thanks for posting this up!
-
Mudassir almost 13 years@Brian D: I am facing the same problem, can you please show me your surface code?
-
Maximus over 12 yearsThanks a lot... this helped a lot!!
-
auselen over 11 yearsFor a native implementation, one can look at libyuv.
-
Matt about 11 yearsThanks - I ended up using the code in post #37 instead (it was posted long after this answer was, but for those of us in the future it works nicely).
-
hico over 10 yearshi. Is it ARGB format or RGB ? How do we do if we only want RGB with the following code ? Thanks a lot for your answer by the way, really help.
-
user140888 about 9 yearsWhat is the array "argb8888" that must be passed to the decodeYUV method?
-
Greg Peckory over 8 yearsThis seems to work for me only sometimes. I've defined the Picture size to be the minimum the camera will take. But I don't know what the
width
,height
parameters of this conversion method should be. Suppose the picture is320x240
res. And the data in is an array of bytes of size8500
. What should thewidth
,height
restrictions be as an argument to the above method? -
Greg Peckory over 8 yearsAlso what should the array length be for int[] out, before I pass it through?
-
Mereb Hayl almost 4 yearsint[] size should be width * height