From 1804badecdfca635a9558a25e32163f634e9f0ec Mon Sep 17 00:00:00 2001
From: Hiroshi Horie <548776+hiroshihorie@users.noreply.github.com>
Date: Mon, 25 Nov 2024 21:08:19 +0900
Subject: [PATCH] Limit scaled frame to source frame dimensions (#513)
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Add logic to prevent scaling up the output frames.
Scaling up the video result frames beyond the resolution of the
device-provided source frames doesn’t make sense.

For example, if the device supports a maximum resolution of 1552x1552,
specifying 3840x2160 will result in an output of 1552x873 (while
maintaining the aspect ratio).
---
 .../Track/Capturers/CameraCapturer.swift      | 24 ++++++++++++++++---
 1 file changed, 21 insertions(+), 3 deletions(-)

diff --git a/Sources/LiveKit/Track/Capturers/CameraCapturer.swift b/Sources/LiveKit/Track/Capturers/CameraCapturer.swift
index 5d41f1a0f..90a8e807e 100644
--- a/Sources/LiveKit/Track/Capturers/CameraCapturer.swift
+++ b/Sources/LiveKit/Track/Capturers/CameraCapturer.swift
@@ -354,9 +354,27 @@ extension LKRTCVideoFrame {
         targetWidth: Int32,
         targetHeight: Int32
     ) -> LKRTCVideoFrame? {
+        // Ensure target dimensions don't exceed source dimensions
+        let scaleWidth: Int32
+        let scaleHeight: Int32
+
+        if targetWidth > width || targetHeight > height {
+            // Calculate scale factor to fit within source dimensions
+            let widthScale = Double(targetWidth) / Double(width) // Scale down factor
+            let heightScale = Double(targetHeight) / Double(height)
+            let scale = max(widthScale, heightScale)
+
+            // Apply scale to target dimensions
+            scaleWidth = Int32(Double(targetWidth) / scale)
+            scaleHeight = Int32(Double(targetHeight) / scale)
+        } else {
+            scaleWidth = targetWidth
+            scaleHeight = targetHeight
+        }
+
         // Calculate aspect ratios
         let sourceRatio = Double(width) / Double(height)
-        let targetRatio = Double(targetWidth) / Double(targetHeight)
+        let targetRatio = Double(scaleWidth) / Double(scaleHeight)
 
         // Calculate crop dimensions
         let (cropWidth, cropHeight): (Int32, Int32)
@@ -379,8 +397,8 @@ extension LKRTCVideoFrame {
             offsetY: offsetY,
             cropWidth: cropWidth,
             cropHeight: cropHeight,
-            scaleWidth: targetWidth,
-            scaleHeight: targetHeight
+            scaleWidth: scaleWidth,
+            scaleHeight: scaleHeight
         ) else { return nil }
 
         return LKRTCVideoFrame(buffer: newBuffer, rotation: rotation, timeStampNs: timeStampNs)