process mp4 file thumbnailing

app/lib/loaded_media.rb

@@ -23,8 +23,8 @@ class LoadedMedia
       )
     when %r{image/jpeg}, %r{image/jpg}, %r{image/png}, %r{image/bmp}
       LoadedMedia::StaticImage.new(media_path)
-    when %r{video/webm}
-      LoadedMedia::Webm.new(media_path)
+    when %r{video/webm}, %r{video/mp4}
+      LoadedMedia::WebmOrMp4.new(media_path)
     else
       return nil
     end

app/lib/loaded_media/webm_or_mp4.rb

@@ -1,7 +1,7 @@
 # typed: strict
 # frozen_string_literal: true
 
-class LoadedMedia::Webm < LoadedMedia
+class LoadedMedia::WebmOrMp4 < LoadedMedia
   include HasColorLogger
 
   ::FFMPEG.logger = Logger.new(nil)
@@ -74,42 +74,33 @@ class LoadedMedia::Webm < LoadedMedia
       File.join(BlobFile::TMP_DIR, "webm-#{frame}-#{SecureRandom.uuid}.png")
     FileUtils.mkdir_p(File.dirname(tmp_path))
 
-    # @media.screenshot(tmp_path, { seek_time: frame_time })
+    # Always seek from the beginning for simplicity and reliability
+    # Add a small safety margin for the last frame to avoid seeking beyond video duration
+    safe_seek_time = [frame_time, @duration - 0.01].min
 
-    # Determine if we should seek from start or end based on where we are in the file
-    past_halfway = frame_time / @duration > 0.5
-
-    cmd = [FFMPEG_BIN, "-y", "-xerror", "-abort_on", "empty_output"] # Overwrite output files
-
-    if past_halfway
-      # For frames in the second half of the file, seek from the end
-      # Convert to a negative offset from the end
-      end_offset = frame_time - @duration
-      cmd.concat(["-sseof", end_offset.round(2).to_s])
-    else
-      # For frames in the first half, seek from the beginning
-      cmd.concat(["-ss", frame_time.round(2).to_s])
-    end
-
-    # Add input file and frame extraction options
-    cmd.concat(
-      [
-        "-i",
-        @media_path, # Input file
-        "-vframes",
-        "1", # Extract one frame
-        "-f",
-        "image2", # Force format to image2
-        "-update",
-        "1", # Update existing file
-        tmp_path,
-      ],
-    )
+    cmd = [
+      FFMPEG_BIN,
+      "-y", # Overwrite output files
+      "-xerror", # Exit on error
+      "-abort_on",
+      "empty_output", # Abort if output is empty
+      "-ss",
+      safe_seek_time.round(2).to_s,
+      "-i",
+      @media_path, # Input file
+      "-vframes",
+      "1", # Extract one frame
+      "-f",
+      "image2", # Force format to image2
+      "-update",
+      "1", # Update existing file
+      tmp_path,
+    ]
 
     _output, error, status = Open3.capture3(*cmd)
     unless status.exitstatus == 0
       $stderr.print error
-      raise "Failed to extract frame with ffmpeg: #{error}"
+      raise "Failed to extract frame with ffmpeg: #{cmd.join(" ")}: #{error}"
     end
 
     # Use the original frame number in the error message

sorbet/rbi/dsl/loaded_media/webm_or_mp4.rbi

@@ -1,11 +1,11 @@
 # typed: true
 
 # DO NOT EDIT MANUALLY
-# This is an autogenerated file for dynamic methods in `LoadedMedia::Webm`.
-# Please instead update this file by running `bin/tapioca dsl LoadedMedia::Webm`.
+# This is an autogenerated file for dynamic methods in `LoadedMedia::WebmOrMp4`.
+# Please instead update this file by running `bin/tapioca dsl LoadedMedia::WebmOrMp4`.
 
 
-class LoadedMedia::Webm
+class LoadedMedia::WebmOrMp4
   sig { returns(ColorLogger) }
   def logger; end
 

spec/lib/loaded_media_spec.rb

@@ -21,6 +21,9 @@ RSpec.describe LoadedMedia do
       .join("test/fixtures/files/images/e621-5421402-animated.webm")
       .to_s
   end
+  let(:mp4_fixture_path) do
+    Rails.root.join("test/fixtures/files/images/bsky-3l6tnjkcgw72y.mp4").to_s
+  end
 
   let(:thumbnail_options) do
     LoadedMedia::ThumbnailOptions.new(
@@ -53,14 +56,23 @@ RSpec.describe LoadedMedia do
     end
 
     context "with a webm file" do
-      it "creates a LoadedMedia::Webm instance" do
+      it "creates a LoadedMedia::WebmOrMp4 instance" do
         media = LoadedMedia.from_file("video/webm", webm_fixture_path)
 
-        expect(media).to be_a(LoadedMedia::Webm)
+        expect(media).to be_a(LoadedMedia::WebmOrMp4)
         expect(media.num_frames).to eq(908)
       end
     end
 
+    context "with an mp4 file" do
+      it "creates a LoadedMedia::WebmOrMp4 instance" do
+        media = LoadedMedia.from_file("video/mp4", mp4_fixture_path)
+
+        expect(media).to be_a(LoadedMedia::WebmOrMp4)
+        expect(media.num_frames).to eq(22)
+      end
+    end
+
     context "with an unsupported file type" do
       it "returns nil" do
         media = LoadedMedia.from_file("application/pdf", jpeg_fixture_path)
@@ -155,5 +167,30 @@ RSpec.describe LoadedMedia do
         expect(FileUtils.compare_file(paths[1], paths[2])).to be false
       end
     end
+
+    context "with an mp4 file" do
+      it "can extract a frame and save a thumbnail" do
+        media = LoadedMedia.from_file("video/mp4", mp4_fixture_path)
+
+        output_path = make_output_path(0)
+        media.write_frame_thumbnail(0, output_path, thumbnail_options)
+      end
+
+      it "creates different frames" do
+        media = LoadedMedia.from_file("video/mp4", mp4_fixture_path)
+
+        paths =
+          [0, 10, media.num_frames - 1].map do |frame|
+            output_path = make_output_path(frame)
+            media.write_frame_thumbnail(frame, output_path, thumbnail_options)
+            output_path
+          end
+
+        expect(paths.uniq.length).to eq(3)
+        expect(FileUtils.compare_file(paths[0], paths[1])).to be false
+        expect(FileUtils.compare_file(paths[0], paths[2])).to be false
+        expect(FileUtils.compare_file(paths[1], paths[2])).to be false
+      end
+    end
   end
 end