Squashed commit of the following:

commit d0c32125df2269621f0b6a85dabe36120a6d3f3b
Merge: fea9399 a6b600d
Author: Collider LI <lhc199652@gmail.com>
Date:   Thu Apr 28 02:12:43 2022 -0400

    Merge branch 'issue-1720' of https://github.com/low-batt/iina into low-batt-issue-1720

commit a6b600d
Author: low-batt <86170219+low-batt@users.noreply.github.com>
Date:   Sun Jul 25 23:14:05 2021 -0400

    Fix memory leaks in FFmpegController, #1720

    The method `getPeeksForFile` in `FFmpegController` is leaking memory
    when generating thumbnails. This commit will:

    - Add a `@try-@finally` block in the while loop to free the packet

    - Replace `av_free` by `av_frame_free`, when freeing an `AVFrame`

    - Add a call to `sws_freeContext` to free the `SwsContext`

    - Replace deprecated method `avcodec_close` with `avcodec_free_context`

    - Add `nullable` annotation to declaration of `probeVideoInfoForFile`

    This is a stopgap fix and does not address all of the potential leaks
    in the method. This commit focuses on the leaks that occur during the
    normal flow when generating thumbnails. Error flows will still leak
    memory. At some point this method should be refactored to always
    properly free memory.

iina/FFmpegController.m

@@ -210,59 +210,60 @@ - (int)getPeeksForFile:(NSString *)file
 
     // Read and decode frame
     while(av_read_frame(pFormatCtx, &packet) >= 0) {
+      @try {
+        // Make sure it's video stream
+        if (packet.stream_index == videoStream) {
 
-      // Make sure it's video stream
-      if (packet.stream_index == videoStream) {
-
-        // Decode video frame
-        if (avcodec_send_packet(pCodecCtx, &packet) < 0)
-          break;
-
-        ret = avcodec_receive_frame(pCodecCtx, pFrame);
-        if (ret < 0) {  // something happened
-          if (ret == AVERROR(EAGAIN))  // input not ready, retry
-            continue;
-          else
+          // Decode video frame
+          if (avcodec_send_packet(pCodecCtx, &packet) < 0)
             break;
-        }
 
-        // Check if duplicated
-        NSNumber *currentTimeStamp = @(pFrame->best_effort_timestamp);
-        if ([_addedTimestamps containsObject:currentTimeStamp]) {
-          double currentTime = CACurrentMediaTime();
-          if (currentTime - _timestamp > 1) {
-            if (self.delegate) {
-              [self.delegate didUpdateThumbnails:NULL forFile: file withProgress: i];
-              _timestamp = currentTime;
+          ret = avcodec_receive_frame(pCodecCtx, pFrame);
+          if (ret < 0) {  // something happened
+            if (ret == AVERROR(EAGAIN))  // input not ready, retry
+              continue;
+            else
+              break;
+          }
+
+          // Check if duplicated
+          NSNumber *currentTimeStamp = @(pFrame->best_effort_timestamp);
+          if ([_addedTimestamps containsObject:currentTimeStamp]) {
+            double currentTime = CACurrentMediaTime();
+            if (currentTime - _timestamp > 1) {
+              if (self.delegate) {
+                [self.delegate didUpdateThumbnails:NULL forFile: file withProgress: i];
+                _timestamp = currentTime;
+              }
             }
+            break;
+          } else {
+            [_addedTimestamps addObject:currentTimeStamp];
           }
+
+          // Convert the frame to RGBA
+          ret = sws_scale(sws_ctx,
+                          (const uint8_t* const *)pFrame->data,
+                          pFrame->linesize,
+                          0,
+                          pCodecCtx->height,
+                          pFrameRGB->data,
+                          pFrameRGB->linesize);
+          CHECK_SUCCESS(ret, @"Cannot convert frame")
+
+          // Save the frame to disk
+          [self saveThumbnail:pFrameRGB
+                        width:pFrameRGB->width
+                       height:pFrameRGB->height
+                        index:i
+                     realTime:(pFrame->best_effort_timestamp * timebaseDouble)
+                      forFile:file];
           break;
-        } else {
-          [_addedTimestamps addObject:currentTimeStamp];
         }
-
-        // Convert the frame to RGBA
-        ret = sws_scale(sws_ctx,
-                        (const uint8_t* const *)pFrame->data,
-                        pFrame->linesize,
-                        0,
-                        pCodecCtx->height,
-                        pFrameRGB->data,
-                        pFrameRGB->linesize);
-        CHECK_SUCCESS(ret, @"Cannot convert frame")
-
-        // Save the frame to disk
-        [self saveThumbnail:pFrameRGB
-                      width:pFrameRGB->width
-                     height:pFrameRGB->height
-                      index:i
-                   realTime:(pFrame->best_effort_timestamp * timebaseDouble)
-                    forFile:file];
-        break;
+      } @finally {
+        // Free the packet
+        av_packet_unref(&packet);
       }
-
-      // Free the packet
-      av_packet_unref(&packet);
     }
   }
   // Free the scaler