Drop undecodable audio streams during remux

CHANGELOG

@@ -1,3 +1,7 @@
+== 8.5.1 2026-11-12
+* Fix re-loading the media after a successful remux
+* Pick decodable audio stream over a non-decodable during remux
+
 == 8.5.0 2026-07-16
 
 Improvements:

lib/ffmpeg/media.rb

@@ -228,6 +228,13 @@ def load!
 
       @size = @metadata[:format][:size].to_i
       @streams = @metadata[:streams].map { |metadata| Stream.new(metadata, stderr) }
+      %i[
+        @video_streams
+        @default_video_stream
+        @audio_streams
+        @default_audio_stream
+        @codec_names
+      ].each { remove_instance_variable(_1) if instance_variable_defined? _1 }
       @tags = @metadata[:format][:tags]
 
       @format_name = @metadata[:format][:format_name]

lib/ffmpeg/remuxer.rb

@@ -52,7 +52,10 @@ def annexb?(media)
     def process(media, output_path, &)
       media = Media.new(media, load: false) unless media.is_a?(Media)
 
-      status = ffmpeg_copy(media, output_path, &)
+      audio_map = decodable_audio_map_patch(media)
+      copy_map = audio_map.nil? ? [] : ['-map', '0:v:0?', *audio_map]
+
+      status = ffmpeg_copy(media, *copy_map, output_path, &)
       return status if status.success?
       return status unless self.class.annexb?(media)
 
@@ -64,7 +67,7 @@ def process(media, output_path, &)
         return annexb_status unless annexb_status.success?
 
         mka_path = File.join(tmpdir, 'remux.mka')
-        mka_status = ffmpeg_copy(media, '-vn', mka_path, &)
+        mka_status = ffmpeg_copy(media, *(audio_map.nil? ? ['-vn'] : audio_map), mka_path, &)
         return mka_status unless mka_status.success?
 
         video = annexb_status.media.first
@@ -125,6 +128,22 @@ def ffmpeg_copy(media, *args, inargs: [], &)
       )
     end
 
+    # Maps the first audio stream that ffmpeg can decode. Without an explicit
+    # map, ffmpeg picks the audio stream with the most channels, which can be an
+    # undecodable one (e.g. iPhone spatial audio, codec_name "unknown") and
+    # drops the usable stream. Returns nil if there is no decodable audio or all
+    # audio streams are decodable
+    def decodable_audio_map_patch(media)
+      decodable, undecodable = media.audio_streams.partition { decodable_audio?(_1) }
+      return nil if undecodable.empty?
+
+      decodable.first&.then { ['-map', "0:#{_1.index}"] }
+    end
+
+    def decodable_audio?(stream)
+      stream.supported? && !['', 'unknown', 'none'].include?(stream.codec_name.to_s)
+    end
+
     def annexb_filter(media)
       ['-bsf:v', "#{media.video_codec_name}_mp4toannexb"]
     end

lib/ffmpeg/version.rb

@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
 module FFMPEG
-  VERSION = '8.5.0'
+  VERSION = '8.5.1'
 end

spec/ffmpeg/media_spec.rb

@@ -48,6 +48,36 @@ module FFMPEG
         subject.load!
       end
 
+      context 'when the media is loaded again after its streams changed' do
+        let(:old_fixture) { fixture_media_file('widescreen-multi-audio.mp4') }
+        let(:new_fixture) { fixture_media_file('widescreen-no-audio.mp4') }
+        let(:tmpdir) { Dir.mktmpdir }
+        let(:path) { File.join(tmpdir, 'media.mp4') }
+
+        before { FileUtils.cp(old_fixture, path) }
+        after { FileUtils.remove_entry(tmpdir) }
+
+        it 'resets the memoized values calculated from the streams' do
+          subject.load!
+          old_streams = subject.streams
+
+          expect(subject.audio_streams).not_to be_empty
+          expect(subject.default_audio_stream).not_to be_nil
+          expect(subject.audio_streams?).to be(true)
+
+          # The spec helper caches ffprobe output by arguments, so drop it to see the new file.
+          FFMPEG.instance_variable_set(:@ffprobe_cache, nil)
+          FileUtils.cp(new_fixture, path)
+          subject.instance_variable_set(:@loaded, false)
+          subject.load!
+
+          expect(subject.streams).not_to eq(old_streams)
+          expect(subject.audio_streams).to be_empty
+          expect(subject.default_audio_stream).to be_nil
+          expect(subject.audio_streams?).to be(false)
+        end
+      end
+
       context 'when the file does not exist' do
         let(:path) { fixture_media_file('missing.mp4') }
 
@@ -451,10 +481,9 @@ module FFMPEG
       video_profile: 'High',
       video_codec_name: 'h264',
       video_bit_rate: 41_401_600,
-      # rubocop:disable Layout/LineLength
+      # rubocop:disable-next Layout/LineLength
       video_overview:
         %r{h264 \(High\) \(avc1 / 0x31637661\), yuvj420p\(pc, bt709/bt709/bt709, (progressive|unknown)\), 3840x2160 \[SAR 1:1 DAR 16:9\]},
-      # rubocop:enable Layout/LineLength
       video_tags: {
         encoder: 'Lavc61.19.100 libx264',
         handler_name: 'VideoHandle',