---
layout: page
title: "Frame Processing"
subtitle: "Process each frame in real time"
description: "Process each frame in real time"
category: docs
order: 6
date: 2018-12-20 20:45:42
disqus: 1
---
We support frame processors that will receive data from the camera preview stream. This is a useful
feature with a wide range of applications. For example, the frames can be sent to a face detector,
a QR code detector, the
[Firebase Machine Learning Kit](https://firebase.google.com/products/ml-kit/), or any other frame consumer.
```java
cameraView.addFrameProcessor(new FrameProcessor() {
@Override
@WorkerThread
public void process(@NonNull Frame frame) {
int rotation = frame.getRotation();
long time = frame.getTime();
Size size = frame.getSize();
int format = frame.getFormat();
if (frame.getDataClass() == byte[].class) {
byte[] data = frame.getData();
// Process byte array...
} else if (frame.getDataClass() == Image.class) {
Image data = frame.getData();
// Process android.media.Image...
}
}
}
```
For your convenience, the `FrameProcessor` method is run in a background thread so you can do your job
in a synchronous fashion. Once the process method returns, internally we will re-use the `Frame` instance and
apply new data to it. So:
- you can do your job synchronously in the `process()` method. This is **recommended**.
- if you must hold the `Frame` instance longer, use `frame = frame.freeze()` to get a frozen instance
that will not be affected. This is **discouraged** because it requires copying the whole array.
### Process synchronously
Processing synchronously, for the duration of the `process()` method, is the recommended way of using
processors, because it solves different issues:
- avoids the need of calling `frame = frame.freeze()` which is a very expensive operation
- the engine will **automatically drop frames** if the `process()` method is busy, so you'll only receive frames that you can handle
- we have already allocated a thread for you, so there's no need to create another
Some frame consumers might have a built-in asynchronous behavior.
But you can still block the `process()` thread until the consumer has returned.
```java
@Override
@WorkerThread
public void process(@NonNull Frame frame) {
// EXAMPLE 1:
// Firebase and Google APIs will often return a Task.
// You can use Tasks.await() to complete the task on the current thread.
// Read: https://developers.google.com/android/guides/tasks#blocking
try {
result = Tasks.await(firebaseDetector.detectInImage(firebaseImage));
catch (Exception e) {
// Firebase task failed.
}
// EXAMPLE 2:
// For other async consumers, you can use, for example, a CountDownLatch.
// Step 1: create the latch.
final CountDownLatch latch = new CountDownLatch(1);
// Step 2: launch async processing here...
// When processing completes or fails, call latch.countDown();
// Step 3: after launching, block the current thread.
latch.await();
}
```
### Frame Data
Starting from `v2.5.0`, the type of data offered by `frame.getData()` depends on the camera engine
that created this frame:
- The Camera1 engine will offer `byte[]` arrays
- The Camera2 engine will offer `android.media.Image` objects
You can check this at runtime by inspecting the data class using `frame.getDataClass()`.
### Frame Size
The Camera2 engine offers the option to set size constraints for the incoming frames.
```java
cameraView.setFrameProcessingMaxWidth(maxWidth);
cameraView.setFrameProcessingMaxHeight(maxWidth);
```
With other engines, these API have no effect.
### Frame Format
The Camera2 engine offers the option to set the frame format as one of the ImageFormat
constants. The default is `ImageFormat.YUV_420_888`.
```java
cameraView.setFrameProcessingFormat(ImageFormat.YUV_420_888);
cameraView.setFrameProcessingFormat(ImageFormat.YUV_422_888);
```
With the Camera1 engine, the incoming format will always be `ImageFormat.NV21`.
You can check which formats are available for use through `CameraOptions.getSupportedFrameProcessingFormats()`.
### XML Attributes
```xml
```
### Related APIs
|Frame API|Type|Description|
|---------|----|-----------|
|`camera.addFrameProcessor(FrameProcessor)`|`-`|Register a `FrameProcessor`.|
|`camera.removeFrameProcessor(FrameProcessor)`|`-`|Removes a `FrameProcessor`.|
|`camera.clearFrameProcessors()`|`-`|Removes all `FrameProcessor`s.|
|`camera.setFrameProcessingMaxWidth(int)`|`-`|Sets the max width for incoming frames.|
|`camera.setFrameProcessingMaxHeight(int)`|`-`|Sets the max height for incoming frames.|
|`camera.getFrameProcessingMaxWidth()`|`int`|Gets the max width for incoming frames.|
|`camera.getFrameProcessingMaxHeight()`|`int`|Gets the max height for incoming frames.|
|`camera.setFrameProcessingFormat(int)`|`-`|Sets the desired format for incoming frames. Should be one of the ImageFormat constants.|
|`camera.getFrameProcessingFormat()`|`-`|Gets the format for incoming frames. One of the ImageFormat constants.|
|`frame.getDataClass()`|`Class`|The class of the data returned by `getData()`. Either `byte[]` or `android.media.Image`.|
|`frame.getData()`|`T`|The current preview frame, in its original orientation.|
|`frame.getTime()`|`long`|The preview timestamp, in `System.currentTimeMillis()` reference.|
|`frame.getRotation()`|`int`|The rotation that should be applied to the byte array in order to see what the user sees.|
|`frame.getSize()`|`Size`|The frame size, before any rotation is applied, to access data.|
|`frame.getFormat()`|`int`|The frame `ImageFormat`. This will always be `ImageFormat.NV21` for now.|
|`frame.freeze()`|`Frame`|Clones this frame and makes it immutable. Can be expensive because requires copying the byte array.|
|`frame.release()`|`-`|Disposes the content of this frame. Should be used on frozen frames to release memory.|