fix(session-replay): revert max key-frame interval to once per video segment (#5156)

Author: philprime

CHANGELOG.md

@@ -24,6 +24,7 @@
 - Improve session replay frame presentation timing calculations (#5133)
 - Use wider compatible video encoding options for Session Replay (#5134)
 - GA of better session replay view renderer V2 (#5054)
+- Revert max key-frame interval to once per session replayvideo segment (#5156)
 
 ## 8.49.2
 

Sources/Swift/Integrations/SessionReplay/SentryOnDemandReplay.swift

@@ -325,11 +325,12 @@ class SentryOnDemandReplay: NSObject, SentryReplayVideoMaker {
                 // where each frame is independent and must be decodable on its own.
                 AVVideoAllowFrameReorderingKey: false,
 
-                // Ensures that every frame is a keyframe (also called an I-frame).
-                // This is crucial in a 1 FPS timelapse context because:
-                // 1. It guarantees that every frame can be displayed without relying on previous frames.
-                // 2. It enables precise seeking and smooth scrubbing across all video players.
-                AVVideoMaxKeyFrameIntervalKey: frameRate // e.g., 1 for 1 FPS
+                // Sets keyframe interval to one I-frame per video segment.
+                // This significantly reduces file size (e.g. from 19KB to 9KB) while maintaining
+                // acceptable seeking granularity. With our 1 FPS recording, this means a keyframe
+                // will be inserted once every 6 seconds of recorded content, but our video segments
+                // will never be longer than 5 seconds, resulting in a maximum of 1 I-frame per video.
+                AVVideoMaxKeyFrameIntervalKey: 6 // 5 + 1 interval for optimal compression
             ] as [String: Any],
 
             // Explicitly sets the video color space to ITU-R BT.709 (the standard for HD video).

Tests/SentryTests/Integrations/SessionReplay/SentryOnDemandReplayTests.swift

@@ -324,7 +324,7 @@ class SentryOnDemandReplayTests: XCTestCase {
         XCTAssertEqual(compressionProperties[AVVideoAverageBitRateKey] as? Int, sut.bitRate)
         XCTAssertEqual(compressionProperties[AVVideoProfileLevelKey] as? String, AVVideoProfileLevelH264MainAutoLevel)
         XCTAssertEqual(compressionProperties[AVVideoAllowFrameReorderingKey] as? Bool, false)
-        XCTAssertEqual(compressionProperties[AVVideoMaxKeyFrameIntervalKey] as? Int, sut.frameRate)
+        XCTAssertEqual(compressionProperties[AVVideoMaxKeyFrameIntervalKey] as? Int, 6)
 
         let colorProperties = try XCTUnwrap(settings[AVVideoColorPropertiesKey] as? [String: Any], "Color properties not found")
 
@@ -353,7 +353,7 @@ class SentryOnDemandReplayTests: XCTestCase {
         XCTAssertEqual(compressionProperties[AVVideoAverageBitRateKey] as? Int, sut.bitRate)
         XCTAssertEqual(compressionProperties[AVVideoProfileLevelKey] as? String, AVVideoProfileLevelH264MainAutoLevel)
         XCTAssertEqual(compressionProperties[AVVideoAllowFrameReorderingKey] as? Bool, false)
-        XCTAssertEqual(compressionProperties[AVVideoMaxKeyFrameIntervalKey] as? Int, sut.frameRate)
+        XCTAssertEqual(compressionProperties[AVVideoMaxKeyFrameIntervalKey] as? Int, 6)
 
         let colorProperties = try XCTUnwrap(settings[AVVideoColorPropertiesKey] as? [String: Any], "Color properties not found")