diff --git a/src/ProcessorPipeline.ts b/src/ProcessorPipeline.ts
index e8d2ddd..62fd046 100644
--- a/src/ProcessorPipeline.ts
+++ b/src/ProcessorPipeline.ts
@@ -46,8 +46,8 @@ export default class ProcessorPipeline implements TrackProcessor<Track.Kind> {
     this.sourceSettings = this.source.getSettings();
     this.sourceDummy = opts.element;
     if (this.sourceDummy instanceof HTMLVideoElement) {
-      this.sourceDummy.height = this.sourceSettings.height!;
-      this.sourceDummy.width = this.sourceSettings.width!;
+      this.sourceDummy.height = this.sourceSettings.height ?? 300;
+      this.sourceDummy.width = this.sourceSettings.width ?? 300;
     }
     if (!(this.sourceDummy instanceof HTMLVideoElement)) {
       throw TypeError('Currently only video transformers are supported');
diff --git a/src/index.ts b/src/index.ts
index 5bc23c5..b7a7ea8 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -2,6 +2,8 @@ import ProcessorPipeline from './ProcessorPipeline';
 import BackgroundTransformer, { SegmenterBaseOptions } from './transformers/BackgroundTransformer';
 import DummyTransformer from './transformers/DummyTransformer';
 
+export * from './transformers/types';
+
 export const BackgroundBlur = (
   blurRadius: number = 10,
   segmenterOptions?: SegmenterBaseOptions,
diff --git a/src/transformers/BackgroundTransformer.ts b/src/transformers/BackgroundTransformer.ts
index bec2648..b81a75d 100644
--- a/src/transformers/BackgroundTransformer.ts
+++ b/src/transformers/BackgroundTransformer.ts
@@ -118,10 +118,10 @@ export default class BackgroundProcessor extends VideoTransformer {
       this.ctx.globalCompositeOperation = 'copy';
       const bitmap = await maskToBitmap(
         this.segmentationResults.categoryMask,
-        this.inputVideo.videoWidth,
-        this.inputVideo.videoHeight,
+        this.segmentationResults.categoryMask.width,
+        this.segmentationResults.categoryMask.height,
       );
-      this.ctx.drawImage(bitmap, 0, 0);
+      this.ctx.drawImage(bitmap, 0, 0, this.canvas.width, this.canvas.height);
       this.ctx.filter = 'none';
       this.ctx.globalCompositeOperation = 'source-in';
       if (this.backgroundImage) {
@@ -162,19 +162,19 @@ export default class BackgroundProcessor extends VideoTransformer {
 
     const bitmap = await maskToBitmap(
       this.segmentationResults.categoryMask,
-      this.inputVideo.videoWidth,
-      this.inputVideo.videoHeight,
+      this.segmentationResults.categoryMask.width,
+      this.segmentationResults.categoryMask.height,
     );
 
     this.ctx.filter = 'blur(3px)';
     this.ctx.globalCompositeOperation = 'copy';
-    this.ctx.drawImage(bitmap, 0, 0);
+    this.ctx.drawImage(bitmap, 0, 0, this.canvas.width, this.canvas.height);
     this.ctx.filter = 'none';
     this.ctx.globalCompositeOperation = 'source-out';
     this.ctx.drawImage(frame, 0, 0, this.canvas.width, this.canvas.height);
     this.ctx.globalCompositeOperation = 'destination-over';
     this.ctx.filter = `blur(${this.blurRadius}px)`;
-    this.ctx.drawImage(frame, 0, 0);
+    this.ctx.drawImage(frame, 0, 0, this.canvas.width, this.canvas.height);
     this.ctx.restore();
   }
 }