diff --git a/examples/objc/AppRTCMobile/ARDAppEngineClient.m b/examples/objc/AppRTCMobile/ARDAppEngineClient.m
index ad7a6c2bf2..dc883621e6 100644
--- a/examples/objc/AppRTCMobile/ARDAppEngineClient.m
+++ b/examples/objc/AppRTCMobile/ARDAppEngineClient.m
@@ -58,7 +58,6 @@ static NSInteger const kARDAppEngineClientErrorBadResponse = -1;
   __weak ARDAppEngineClient *weakSelf = self;
   [NSURLConnection sendAsyncRequest:request
                   completionHandler:^(NSURLResponse *response, NSData *data, NSError *error) {
-                    ARDAppEngineClient *strongSelf = weakSelf;
                     if (error) {
                       if (completionHandler) {
                         completionHandler(nil, error);
@@ -102,7 +101,6 @@ static NSInteger const kARDAppEngineClientErrorBadResponse = -1;
                   completionHandler:^(NSURLResponse *response,
                                       NSData *data,
                                       NSError *error) {
-    ARDAppEngineClient *strongSelf = weakSelf;
     if (error) {
       if (completionHandler) {
         completionHandler(nil, error);
diff --git a/examples/objc/AppRTCMobile/ARDCaptureController.m b/examples/objc/AppRTCMobile/ARDCaptureController.m
index 6830e88c23..0145c17091 100644
--- a/examples/objc/AppRTCMobile/ARDCaptureController.m
+++ b/examples/objc/AppRTCMobile/ARDCaptureController.m
@@ -21,7 +21,7 @@
 
 - (instancetype)initWithCapturer:(RTCCameraVideoCapturer *)capturer
                         settings:(ARDSettingsModel *)settings {
-  if ([super init]) {
+  if (self = [super init]) {
     _capturer = capturer;
     _settings = settings;
     _usingFrontCamera = YES;
diff --git a/examples/objc/AppRTCMobile/ARDSettingsModel.m b/examples/objc/AppRTCMobile/ARDSettingsModel.m
index a4eea731d4..7d731fd4bf 100644
--- a/examples/objc/AppRTCMobile/ARDSettingsModel.m
+++ b/examples/objc/AppRTCMobile/ARDSettingsModel.m
@@ -168,8 +168,6 @@ NS_ASSUME_NONNULL_BEGIN
 }
 
 - (void)registerStoreDefaults {
-  NSString *defaultVideoResolutionSetting = [self defaultVideoResolutionSetting];
-
   NSData *codecData = [NSKeyedArchiver archivedDataWithRootObject:[self defaultVideoCodecSetting]];
   [ARDSettingsStore setDefaultsForVideoResolution:[self defaultVideoResolutionSetting]
                                        videoCodec:codecData
diff --git a/modules/video_capture/objc/rtc_video_capture_objc.mm b/modules/video_capture/objc/rtc_video_capture_objc.mm
index bea9bb79ff..92bfd64fa3 100644
--- a/modules/video_capture/objc/rtc_video_capture_objc.mm
+++ b/modules/video_capture/objc/rtc_video_capture_objc.mm
@@ -42,7 +42,7 @@ using namespace webrtc::videocapturemodule;
 @synthesize frameRotation = _framRotation;
 
 - (id)initWithOwner:(VideoCaptureIos*)owner {
-  if (self == [super init]) {
+  if (self = [super init]) {
     _owner = owner;
     _captureSession = [[AVCaptureSession alloc] init];
 #if defined(WEBRTC_IOS)
diff --git a/sdk/objc/Framework/Classes/Common/RTCFileLogger.mm b/sdk/objc/Framework/Classes/Common/RTCFileLogger.mm
index 15461f44fa..6acb942a3a 100644
--- a/sdk/objc/Framework/Classes/Common/RTCFileLogger.mm
+++ b/sdk/objc/Framework/Classes/Common/RTCFileLogger.mm
@@ -124,7 +124,7 @@ const char *kRTCFileLoggerRotatingLogPrefix = "rotating_log";
   _logSink.reset();
 }
 
-- (NSData *)logData {
+- (nullable NSData *)logData {
   if (_hasStarted) {
     return nil;
   }
diff --git a/sdk/objc/Framework/Classes/PeerConnection/RTCAudioTrack.mm b/sdk/objc/Framework/Classes/PeerConnection/RTCAudioTrack.mm
index fffbd7cfe5..e26088f59d 100644
--- a/sdk/objc/Framework/Classes/PeerConnection/RTCAudioTrack.mm
+++ b/sdk/objc/Framework/Classes/PeerConnection/RTCAudioTrack.mm
@@ -31,7 +31,7 @@
   std::string nativeId = [NSString stdStringForString:trackId];
   rtc::scoped_refptr<webrtc::AudioTrackInterface> track =
       factory.nativeFactory->CreateAudioTrack(nativeId, source.nativeAudioSource);
-  if ([self initWithNativeTrack:track type:RTCMediaStreamTrackTypeAudio]) {
+  if (self = [self initWithNativeTrack:track type:RTCMediaStreamTrackTypeAudio]) {
     _source = source;
   }
   return self;
diff --git a/sdk/objc/Framework/Classes/PeerConnection/RTCConfiguration+Private.h b/sdk/objc/Framework/Classes/PeerConnection/RTCConfiguration+Private.h
index bf00d1870f..d9a991650b 100644
--- a/sdk/objc/Framework/Classes/PeerConnection/RTCConfiguration+Private.h
+++ b/sdk/objc/Framework/Classes/PeerConnection/RTCConfiguration+Private.h
@@ -62,8 +62,7 @@ NS_ASSUME_NONNULL_BEGIN
  * RTCConfiguration struct representation of this RTCConfiguration. This is
  * needed to pass to the underlying C++ APIs.
  */
-- (webrtc::PeerConnectionInterface::RTCConfiguration *)
-    createNativeConfiguration;
+- (nullable webrtc::PeerConnectionInterface::RTCConfiguration *)createNativeConfiguration;
 
 - (instancetype)initWithNativeConfiguration:
     (const webrtc::PeerConnectionInterface::RTCConfiguration &)config NS_DESIGNATED_INITIALIZER;
diff --git a/sdk/objc/Framework/Classes/PeerConnection/RTCEncodedImage.mm b/sdk/objc/Framework/Classes/PeerConnection/RTCEncodedImage.mm
index ef2840f157..467f225b58 100644
--- a/sdk/objc/Framework/Classes/PeerConnection/RTCEncodedImage.mm
+++ b/sdk/objc/Framework/Classes/PeerConnection/RTCEncodedImage.mm
@@ -48,7 +48,7 @@
     _frameType = static_cast<RTCFrameType>(encodedImage._frameType);
     _rotation = static_cast<RTCVideoRotation>(encodedImage.rotation_);
     _completeFrame = encodedImage._completeFrame;
-    _qp = encodedImage.qp_ == -1 ? nil : @(encodedImage.qp_);
+    _qp = @(encodedImage.qp_);
     _contentType = (encodedImage.content_type_ == webrtc::VideoContentType::SCREENSHARE) ?
         RTCVideoContentTypeScreenshare :
         RTCVideoContentTypeUnspecified;
diff --git a/sdk/objc/Framework/Classes/PeerConnection/RTCFileVideoCapturer.m b/sdk/objc/Framework/Classes/PeerConnection/RTCFileVideoCapturer.m
index 07cb2c6668..7e27bf2df3 100644
--- a/sdk/objc/Framework/Classes/PeerConnection/RTCFileVideoCapturer.m
+++ b/sdk/objc/Framework/Classes/PeerConnection/RTCFileVideoCapturer.m
@@ -139,6 +139,7 @@ typedef NS_ENUM(NSInteger, RTCFileVideoCapturerStatus) {
   }
   if (CMSampleBufferGetNumSamples(sampleBuffer) != 1 || !CMSampleBufferIsValid(sampleBuffer) ||
       !CMSampleBufferDataIsReady(sampleBuffer)) {
+    CFRelease(sampleBuffer);
     [self readNextBuffer];
     return;
   }
diff --git a/sdk/objc/Framework/Classes/PeerConnection/RTCPeerConnection+DataChannel.mm b/sdk/objc/Framework/Classes/PeerConnection/RTCPeerConnection+DataChannel.mm
index 80b510898c..d17d9ac2f4 100644
--- a/sdk/objc/Framework/Classes/PeerConnection/RTCPeerConnection+DataChannel.mm
+++ b/sdk/objc/Framework/Classes/PeerConnection/RTCPeerConnection+DataChannel.mm
@@ -16,9 +16,8 @@
 
 @implementation RTCPeerConnection (DataChannel)
 
-- (RTCDataChannel *)dataChannelForLabel:(NSString *)label
-                          configuration:
-    (RTCDataChannelConfiguration *)configuration {
+- (nullable RTCDataChannel *)dataChannelForLabel:(NSString *)label
+                                   configuration:(RTCDataChannelConfiguration *)configuration {
   std::string labelString = [NSString stdStringForString:label];
   const webrtc::DataChannelInit nativeInit =
       configuration.nativeDataChannelInit;
diff --git a/sdk/objc/Framework/Classes/PeerConnection/RTCRtpReceiver.mm b/sdk/objc/Framework/Classes/PeerConnection/RTCRtpReceiver.mm
index 0888f24b0a..cb2771a29c 100644
--- a/sdk/objc/Framework/Classes/PeerConnection/RTCRtpReceiver.mm
+++ b/sdk/objc/Framework/Classes/PeerConnection/RTCRtpReceiver.mm
@@ -58,7 +58,7 @@ void RtpReceiverDelegateAdapter::OnFirstPacketReceived(
   }
 }
 
-- (RTCMediaStreamTrack *)track {
+- (nullable RTCMediaStreamTrack *)track {
   rtc::scoped_refptr<webrtc::MediaStreamTrackInterface> nativeTrack(
     _nativeRtpReceiver->track());
   if (nativeTrack) {
diff --git a/sdk/objc/Framework/Classes/PeerConnection/RTCSessionDescription+Private.h b/sdk/objc/Framework/Classes/PeerConnection/RTCSessionDescription+Private.h
index 5811a5abc5..4c58fa726a 100644
--- a/sdk/objc/Framework/Classes/PeerConnection/RTCSessionDescription+Private.h
+++ b/sdk/objc/Framework/Classes/PeerConnection/RTCSessionDescription+Private.h
@@ -21,8 +21,7 @@ NS_ASSUME_NONNULL_BEGIN
  * RTCSessionDescription object. This is needed to pass to the underlying C++
  * APIs.
  */
-@property(nonatomic, readonly)
-    webrtc::SessionDescriptionInterface *nativeDescription;
+@property(nonatomic, readonly, nullable) webrtc::SessionDescriptionInterface *nativeDescription;
 
 /**
  * Initialize an RTCSessionDescription from a native
diff --git a/sdk/objc/Framework/Classes/PeerConnection/RTCVideoTrack.mm b/sdk/objc/Framework/Classes/PeerConnection/RTCVideoTrack.mm
index 9fa6111411..2f03110739 100644
--- a/sdk/objc/Framework/Classes/PeerConnection/RTCVideoTrack.mm
+++ b/sdk/objc/Framework/Classes/PeerConnection/RTCVideoTrack.mm
@@ -32,7 +32,7 @@
   rtc::scoped_refptr<webrtc::VideoTrackInterface> track =
       factory.nativeFactory->CreateVideoTrack(nativeId,
                                               source.nativeVideoSource);
-  if ([self initWithNativeTrack:track type:RTCMediaStreamTrackTypeVideo]) {
+  if (self = [self initWithNativeTrack:track type:RTCMediaStreamTrackTypeVideo]) {
     _source = source;
   }
   return self;
diff --git a/sdk/objc/Framework/Classes/PeerConnection/RTCWrappedNativeVideoDecoder.mm b/sdk/objc/Framework/Classes/PeerConnection/RTCWrappedNativeVideoDecoder.mm
index 7d82c5b8e3..7529ebf028 100644
--- a/sdk/objc/Framework/Classes/PeerConnection/RTCWrappedNativeVideoDecoder.mm
+++ b/sdk/objc/Framework/Classes/PeerConnection/RTCWrappedNativeVideoDecoder.mm
@@ -49,7 +49,7 @@
 - (NSInteger)decode:(RTCEncodedImage *)encodedImage
           missingFrames:(BOOL)missingFrames
     fragmentationHeader:(RTCRtpFragmentationHeader *)fragmentationHeader
-      codecSpecificInfo:(__nullable id<RTCCodecSpecificInfo>)info
+      codecSpecificInfo:(nullable id<RTCCodecSpecificInfo>)info
            renderTimeMs:(int64_t)renderTimeMs {
   RTC_NOTREACHED();
   return 0;
diff --git a/sdk/objc/Framework/Classes/PeerConnection/RTCWrappedNativeVideoEncoder.mm b/sdk/objc/Framework/Classes/PeerConnection/RTCWrappedNativeVideoEncoder.mm
index 9d2f81b3cc..8988e6d76e 100644
--- a/sdk/objc/Framework/Classes/PeerConnection/RTCWrappedNativeVideoEncoder.mm
+++ b/sdk/objc/Framework/Classes/PeerConnection/RTCWrappedNativeVideoEncoder.mm
@@ -47,7 +47,7 @@
 }
 
 - (NSInteger)encode:(RTCVideoFrame *)frame
-    codecSpecificInfo:(id<RTCCodecSpecificInfo>)info
+    codecSpecificInfo:(nullable id<RTCCodecSpecificInfo>)info
            frameTypes:(NSArray<NSNumber *> *)frameTypes {
   RTC_NOTREACHED();
   return 0;
diff --git a/sdk/objc/Framework/Classes/VideoToolbox/RTCVideoDecoderH264.mm b/sdk/objc/Framework/Classes/VideoToolbox/RTCVideoDecoderH264.mm
index debd504790..2f4b6bd72c 100644
--- a/sdk/objc/Framework/Classes/VideoToolbox/RTCVideoDecoderH264.mm
+++ b/sdk/objc/Framework/Classes/VideoToolbox/RTCVideoDecoderH264.mm
@@ -22,6 +22,7 @@
 #import "WebRTC/RTCVideoFrame.h"
 #import "WebRTC/RTCVideoFrameBuffer.h"
 #import "helpers.h"
+#import "scoped_cftyperef.h"
 
 #if defined(WEBRTC_IOS)
 #import "Common/RTCUIApplicationStatusObserver.h"
@@ -99,7 +100,7 @@ void decompressionOutputCallback(void *decoderRef,
 - (NSInteger)decode:(RTCEncodedImage *)inputImage
           missingFrames:(BOOL)missingFrames
     fragmentationHeader:(RTCRtpFragmentationHeader *)fragmentationHeader
-      codecSpecificInfo:(__nullable id<RTCCodecSpecificInfo>)info
+      codecSpecificInfo:(nullable id<RTCCodecSpecificInfo>)info
            renderTimeMs:(int64_t)renderTimeMs {
   RTC_DCHECK(inputImage.buffer);
 
@@ -119,19 +120,22 @@ void decompressionOutputCallback(void *decoderRef,
     return WEBRTC_VIDEO_CODEC_NO_OUTPUT;
   }
 #endif
-  CMVideoFormatDescriptionRef inputFormat = nullptr;
   if (webrtc::H264AnnexBBufferHasVideoFormatDescription((uint8_t *)inputImage.buffer.bytes,
                                                         inputImage.buffer.length)) {
-    inputFormat = webrtc::CreateVideoFormatDescription((uint8_t *)inputImage.buffer.bytes,
-                                                       inputImage.buffer.length);
+    rtc::ScopedCFTypeRef<CMVideoFormatDescriptionRef> inputFormat =
+        rtc::ScopedCF(webrtc::CreateVideoFormatDescription((uint8_t *)inputImage.buffer.bytes,
+                                                           inputImage.buffer.length));
     if (inputFormat) {
       // Check if the video format has changed, and reinitialize decoder if
       // needed.
-      if (!CMFormatDescriptionEqual(inputFormat, _videoFormat)) {
-        [self setVideoFormat:inputFormat];
-        [self resetDecompressionSession];
+      if (!CMFormatDescriptionEqual(inputFormat.get(), _videoFormat)) {
+        [self setVideoFormat:inputFormat.get()];
+
+        int resetDecompressionSessionError = [self resetDecompressionSession];
+        if (resetDecompressionSessionError != WEBRTC_VIDEO_CODEC_OK) {
+          return resetDecompressionSessionError;
+        }
       }
-      CFRelease(inputFormat);
     }
   }
   if (!_videoFormat) {
diff --git a/sdk/objc/Framework/Classes/VideoToolbox/RTCVideoEncoderH264.mm b/sdk/objc/Framework/Classes/VideoToolbox/RTCVideoEncoderH264.mm
index 86855a293c..a818c27d1e 100644
--- a/sdk/objc/Framework/Classes/VideoToolbox/RTCVideoEncoderH264.mm
+++ b/sdk/objc/Framework/Classes/VideoToolbox/RTCVideoEncoderH264.mm
@@ -340,7 +340,7 @@ CFStringRef ExtractProfile(webrtc::SdpVideoFormat videoFormat) {
 }
 
 - (NSInteger)encode:(RTCVideoFrame *)frame
-    codecSpecificInfo:(id<RTCCodecSpecificInfo>)codecSpecificInfo
+    codecSpecificInfo:(nullable id<RTCCodecSpecificInfo>)codecSpecificInfo
            frameTypes:(NSArray<NSNumber *> *)frameTypes {
   RTC_DCHECK_EQ(frame.width, _width);
   RTC_DCHECK_EQ(frame.height, _height);
diff --git a/sdk/objc/Framework/Headers/WebRTC/RTCFileLogger.h b/sdk/objc/Framework/Headers/WebRTC/RTCFileLogger.h
index 5656b7bf43..1e8a591b73 100644
--- a/sdk/objc/Framework/Headers/WebRTC/RTCFileLogger.h
+++ b/sdk/objc/Framework/Headers/WebRTC/RTCFileLogger.h
@@ -69,7 +69,7 @@ RTC_EXPORT
 
 // Returns the current contents of the logs, or nil if start has been called
 // without a stop.
-- (NSData *)logData;
+- (nullable NSData *)logData;
 
 @end
 
diff --git a/sdk/objc/Framework/Headers/WebRTC/RTCPeerConnection.h b/sdk/objc/Framework/Headers/WebRTC/RTCPeerConnection.h
index 7b0c4492f4..a4c113b1d6 100644
--- a/sdk/objc/Framework/Headers/WebRTC/RTCPeerConnection.h
+++ b/sdk/objc/Framework/Headers/WebRTC/RTCPeerConnection.h
@@ -212,8 +212,8 @@ RTC_EXPORT
 @interface RTCPeerConnection (DataChannel)
 
 /** Create a new data channel with the given label and configuration. */
-- (RTCDataChannel *)dataChannelForLabel:(NSString *)label
-    configuration:(RTCDataChannelConfiguration *)configuration;
+- (nullable RTCDataChannel *)dataChannelForLabel:(NSString *)label
+                                   configuration:(RTCDataChannelConfiguration *)configuration;
 
 @end
 
diff --git a/sdk/objc/Framework/Headers/WebRTC/RTCRtpReceiver.h b/sdk/objc/Framework/Headers/WebRTC/RTCRtpReceiver.h
index 6c39a25310..6156db9f93 100644
--- a/sdk/objc/Framework/Headers/WebRTC/RTCRtpReceiver.h
+++ b/sdk/objc/Framework/Headers/WebRTC/RTCRtpReceiver.h
@@ -65,7 +65,7 @@ RTC_EXPORT
  *  RTCMediaStreamTrack. Use isEqual: instead of == to compare
  *  RTCMediaStreamTrack instances.
  */
-@property(nonatomic, readonly) RTCMediaStreamTrack *track;
+@property(nonatomic, readonly, nullable) RTCMediaStreamTrack *track;
 
 /** The delegate for this RtpReceiver. */
 @property(nonatomic, weak) id<RTCRtpReceiverDelegate> delegate;
diff --git a/sdk/objc/Framework/Headers/WebRTC/RTCVideoCodec.h b/sdk/objc/Framework/Headers/WebRTC/RTCVideoCodec.h
index ab17ce4fc8..470eb02326 100644
--- a/sdk/objc/Framework/Headers/WebRTC/RTCVideoCodec.h
+++ b/sdk/objc/Framework/Headers/WebRTC/RTCVideoCodec.h
@@ -148,7 +148,7 @@ RTC_EXPORT
                        numberOfCores:(int)numberOfCores;
 - (NSInteger)releaseEncoder;
 - (NSInteger)encode:(RTCVideoFrame *)frame
-    codecSpecificInfo:(id<RTCCodecSpecificInfo>)info
+    codecSpecificInfo:(nullable id<RTCCodecSpecificInfo>)info
            frameTypes:(NSArray<NSNumber *> *)frameTypes;
 - (int)setBitrate:(uint32_t)bitrateKbit framerate:(uint32_t)framerate;
 - (NSString *)implementationName;
@@ -171,7 +171,7 @@ RTC_EXPORT
 - (NSInteger)decode:(RTCEncodedImage *)encodedImage
           missingFrames:(BOOL)missingFrames
     fragmentationHeader:(RTCRtpFragmentationHeader *)fragmentationHeader
-      codecSpecificInfo:(__nullable id<RTCCodecSpecificInfo>)info
+      codecSpecificInfo:(nullable id<RTCCodecSpecificInfo>)info
            renderTimeMs:(int64_t)renderTimeMs;
 - (NSString *)implementationName;
 
diff --git a/sdk/objc/Framework/Headers/WebRTC/RTCVideoCodecFactory.h b/sdk/objc/Framework/Headers/WebRTC/RTCVideoCodecFactory.h
index c77593ff97..0ef2c8a655 100644
--- a/sdk/objc/Framework/Headers/WebRTC/RTCVideoCodecFactory.h
+++ b/sdk/objc/Framework/Headers/WebRTC/RTCVideoCodecFactory.h
@@ -19,7 +19,7 @@ NS_ASSUME_NONNULL_BEGIN
 RTC_EXPORT
 @protocol RTCVideoEncoderFactory <NSObject>
 
-- (id<RTCVideoEncoder>)createEncoder:(RTCVideoCodecInfo *)info;
+- (nullable id<RTCVideoEncoder>)createEncoder:(RTCVideoCodecInfo *)info;
 - (NSArray<RTCVideoCodecInfo *> *)supportedCodecs;  // TODO(andersc): "supportedFormats" instead?
 
 @end
@@ -28,7 +28,7 @@ RTC_EXPORT
 RTC_EXPORT
 @protocol RTCVideoDecoderFactory <NSObject>
 
-- (id<RTCVideoDecoder>)createDecoder:(RTCVideoCodecInfo *)info;
+- (nullable id<RTCVideoDecoder>)createDecoder:(RTCVideoCodecInfo *)info;
 - (NSArray<RTCVideoCodecInfo *> *)supportedCodecs;  // TODO(andersc): "supportedFormats" instead?
 
 @end