docs: Update Format.pixelFormat documentation

docs/docs/guides/FRAME_PROCESSORS.mdx

@@ -160,6 +160,13 @@ const frameProcessor = useFrameProcessor((frame) => {
 
 Check out [**Frame Processor community plugins**](/docs/guides/frame-processor-plugin-list) to discover plugins, or [**start creating a plugin yourself**](/docs/guides/frame-processors-plugins-overview)!
 
+### Selecting a Format for a Frame Processor
+
+When running frame processors, it is often important to choose an appropriate [format](/docs/guides/formats). Here are some general tips to consider:
+
+* If you are running heavy AI/ML calculations in your frame processor, make sure to [select a format](/docs/guides/formats) that has a lower resolution to optimize it's performance.
+* Sometimes a frame processor plugin only works with specific [pixel formats](/docs/api/interfaces/CameraDeviceFormat#pixelformat). Some plugins (like MLKit) don't work with `x420`.
+
 ### Benchmarks
 
 Frame Processors are _really_ fast. I have used [MLKit Vision Image Labeling](https://firebase.google.com/docs/ml-kit/ios/label-images) to label 4k Camera frames in realtime, and measured the following results:

ios/CameraView+RecordVideo.swift

@@ -110,7 +110,7 @@ extension CameraView: AVCaptureVideoDataOutputSampleBufferDelegate, AVCaptureAud
         callback.reject(error: .capture(.createRecorderError(message: "Failed to get video settings!")))
         return
       }
-      // get pixel format (420f, 420v)
+      // get pixel format (420f, 420v, x420)
       let pixelFormat = CMFormatDescriptionGetMediaSubType(videoInput.device.activeFormat.formatDescription)
       self.recordingSession!.initializeVideoWriter(withSettings: videoSettings,
                                                    pixelFormat: pixelFormat)

src/CameraDevice.ts

@@ -173,7 +173,9 @@ export interface CameraDeviceFormat {
    */
   videoStabilizationModes: VideoStabilizationMode[];
   /**
-   * Specifies the pixel format on iOS. e.g. 420v, 420f
+   * Specifies this format's pixel format. The pixel format specifies how the individual pixels are interpreted as a visual image.
+   *
+   * The most common format is `420v`. Some formats (like `x420`) are not compatible with some frame processor plugins (e.g. MLKit)
    */
   pixelFormat: PixelFormat;
 }