Add fallback for keyframe-only trickplay extraction

Keyframe-only trickplay image extraction can fail for some media
files. The current behavior is to skip the media file and try again
on the next run, which will fail again.

This adds a fallback to regular non-keyframe-only extraction for
failed runs, so the extraction can complete.

MediaBrowser.MediaEncoding/Encoder/MediaEncoder.cs

@@ -827,7 +827,7 @@ namespace MediaBrowser.MediaEncoding.Encoder
         }
 
         /// <inheritdoc />
-        public Task<string> ExtractVideoImagesOnIntervalAccelerated(
+        public async Task<string> ExtractVideoImagesOnIntervalAccelerated(
             string inputFile,
             string container,
             MediaSourceInfo mediaSource,
@@ -918,18 +918,34 @@ namespace MediaBrowser.MediaEncoding.Encoder
                 inputArg = "-hwaccel_flags +low_priority " + inputArg;
             }
 
-            if (enableKeyFrameOnlyExtraction)
-            {
-                inputArg = "-skip_frame nokey " + inputArg;
-            }
-
             var filterParam = encodingHelper.GetVideoProcessingFilterParam(jobState, options, vidEncoder).Trim();
             if (string.IsNullOrWhiteSpace(filterParam))
             {
                 throw new InvalidOperationException("EncodingHelper returned empty or invalid filter parameters.");
             }
 
-            return ExtractVideoImagesOnIntervalInternal(inputArg, filterParam, vidEncoder, threads, qualityScale, priority, cancellationToken);
+            try
+            {
+                return await ExtractVideoImagesOnIntervalInternal(
+                    (enableKeyFrameOnlyExtraction ? "-skip_frame nokey " : string.Empty) + inputArg,
+                    filterParam,
+                    vidEncoder,
+                    threads,
+                    qualityScale,
+                    priority,
+                    cancellationToken).ConfigureAwait(false);
+            }
+            catch (FfmpegException ex)
+            {
+                if (!enableKeyFrameOnlyExtraction)
+                {
+                    throw;
+                }
+
+                _logger.LogWarning(ex, "I-frame trickplay extraction failed, will attempt standard way. Input: {InputFile}", inputFile);
+            }
+
+            return await ExtractVideoImagesOnIntervalInternal(inputArg, filterParam, vidEncoder, threads, qualityScale, priority, cancellationToken).ConfigureAwait(false);
         }
 
         private async Task<string> ExtractVideoImagesOnIntervalInternal(