Target duration set to floor instead of error

src/containers/hls/lib/playlists.rb

@@ -139,14 +139,16 @@ def measure(playlist)
     # small TARGETDURATION and must not be dragged up.
     def harmonize_target_duration
       playlists = @video_rungs.map(&:playlist) + [@audio.playlist]
-      target = playlists.map { |pl| required_target_duration(pl) }.max
-
+      longest = playlists.map { |pl| required_target_duration(pl) }.max
       range = @s::TARGET_DURATION_RANGE
-      unless range.cover?(target)
-        raise "EXT-X-TARGETDURATION is #{target}s, outside the allowed range " \
-              "#{range.min}-#{range.max}s. Adjust TARGET (and HLS_TIME, which is " \
-              "the min_segment floor that evicts grid points near a break and so " \
-              "lengthens the adjacent segment)."
+
+      # use the range min as a floor (b/c of breaks, there may be shorter segments; that's fine)
+      # the boundaries logic should prevent this from happening, but just in case,
+      # do check no segment exceeds the range max; that's not ok (re: RFC 8216)
+      target = [longest, range.min].max
+      if target > range.max
+        raise "EXT-X-TARGETDURATION is #{target}s, above the allowed maximum " \
+              "#{range.max}s. Lower MAX_SEG, which caps segment length."
       end
 
       playlists.each do |pl|

src/containers/hls/test/playlists_test.rb

@@ -127,15 +127,26 @@ def playlists_for(dir, breaks: [])
       end
     end
 
-    it "refuses to write a playlist outside the allowed range" do
+    it "refuses to write a playlist whose segments exceed the allowed maximum" do
       Dir.mktmpdir do |dir|
         build_package(dir, video_durations: [14.0, 6.0])
         err = _ { playlists_for(dir).write_all }.must_raise RuntimeError
-        _(err.message).must_match(/outside the allowed range/)
+        _(err.message).must_match(/above the allowed maximum/)
         # and must not leave a master behind
         _(File.exist?(File.join(dir, "index.m3u8"))).must_equal false
       end
     end
+
+    it "declares the range floor when every segment is shorter than it" do
+      Dir.mktmpdir do |dir|
+        build_package(dir, video_durations: [5.3, 4.9, 3.55],
+          audio_durations: [5.290667, 4.9, 3.55])
+        playlists_for(dir).write_all
+        %w[720p.m3u8 480p.m3u8 audio.m3u8].each do |name|
+          _(File.read(File.join(dir, name))).must_include "#EXT-X-TARGETDURATION:6"
+        end
+      end
+    end
   end
 
   describe "EXT-X-VERSION floor" do