Patch for FFMPEG to fix broken channel disabling behavior

ffmpeg-3.1.3-defaultstreams.patch

diff --git a/libavformat/movenc.c b/libavformat/movenc.c
--- a/libavformat/movenc.c
+++ b/libavformat/movenc.c
@@ -5208,26 +5208,46 @@ static void enable_tracks(AVFormatContext *s)
             st->codecpar->codec_type >= AVMEDIA_TYPE_NB)
             continue;
 
+        // note the first stream number for each type
         if (first[st->codecpar->codec_type] < 0)
             first[st->codecpar->codec_type] = i;
-        if (st->disposition & AV_DISPOSITION_DEFAULT) {
-            mov->tracks[i].flags |= MOV_TRACK_ENABLED;
-            enabled[st->codecpar->codec_type]++;
-        }
+
+        // note whether each media type has any enabled streams
+        if (st->disposition & AV_DISPOSITION_DEFAULT)
+            enabled[st->codecpar->codec_type] = 1;
+
+        // clear the enables for each stream and track
+        st->disposition &= ~AV_DISPOSITION_DEFAULT;
+        mov->tracks[i].flags &= ~MOV_TRACK_ENABLED;
     }
 
+    // for each media type, if no stream was explicitly enabled
+    // then enable the first one found for that type
     for (i = 0; i < AVMEDIA_TYPE_NB; i++) {
         switch (i) {
         case AVMEDIA_TYPE_VIDEO:
         case AVMEDIA_TYPE_AUDIO:
         case AVMEDIA_TYPE_SUBTITLE:
-            if (enabled[i] > 1)
-                mov->per_stream_grouping = 1;
             if (!enabled[i] && first[i] >= 0)
-                mov->tracks[first[i]].flags |= MOV_TRACK_ENABLED;
+                enabled[i] = 1;
             break;
         }
     }
+
+    // translate the first enabled stream of each media type
+    // into its stream being default and its output track being enabled
+    for (i = 0; i < AVMEDIA_TYPE_NB; i++) {
+        switch (i) {
+            case AVMEDIA_TYPE_VIDEO:
+            case AVMEDIA_TYPE_AUDIO:
+            case AVMEDIA_TYPE_SUBTITLE:
+                if (enabled[i]) {
+                    s->streams[first[i]]->disposition |= AV_DISPOSITION_DEFAULT;
+                    mov->tracks[first[i]].flags |= MOV_TRACK_ENABLED;
+                }
+                break;
+        }
+    }
 }
 
 static void mov_free(AVFormatContext *s)

ffmpeg.rb

class Ffmpeg < Formula
  desc "Play, record, convert, and stream audio and video"
  homepage "https://ffmpeg.org/"
  url "https://ffmpeg.org/releases/ffmpeg-3.1.3.tar.bz2"
  sha256 "58bc89c65dd114d874efbf76f76368d03b5e407f0a3f42d5b40801c280968a38"
  head "https://github.com/FFmpeg/FFmpeg.git"

  patch do
    url "https://gist.githubusercontent.com/ptb/63ae6ddfe438d4ea2f589698e58cf481/raw/193b174f854f15750715f1bb8e2d1d9347d1b9dc/ffmpeg-3.1.3-defaultstreams.patch"
    sha256 "17ca8122435f57a403253346ce03e7cc6eaf8986bea29e707a97f9941ca24fa0"
  end

  bottle do
    sha256 "72c4a03a0c98e7e005cc2ea5bfd6428a667e3906d6ca7861fdbbe6612f719d99" => :sierra
    sha256 "3e618cc1fde5bb1fee315eb73573e99eded3c1bbac2d22571f397568ea6d0e40" => :el_capitan
    sha256 "d9721a85c48917416563fff84d01dd1e8aa33c73334906c1459d66463629f8f9" => :yosemite
    sha256 "0c93e86b2299aa4ec67a91b29a8246d49f7d73edf959305954b1d664aedb7390" => :mavericks
  end

  option "without-x264", "Disable H.264 encoder"
  option "without-lame", "Disable MP3 encoder"
  option "without-xvid", "Disable Xvid MPEG-4 video encoder"
  option "without-qtkit", "Disable deprecated QuickTime framework"

  option "with-rtmpdump", "Enable RTMP protocol"
  option "with-libass", "Enable ASS/SSA subtitle format"
  option "with-opencore-amr", "Enable Opencore AMR NR/WB audio format"
  option "with-openjpeg", "Enable JPEG 2000 image format"
  option "with-openssl", "Enable SSL support"
  option "with-libssh", "Enable SFTP protocol via libssh"
  option "with-schroedinger", "Enable Dirac video format"
  option "with-ffplay", "Enable FFplay media player"
  option "with-tools", "Enable additional FFmpeg tools"
  option "with-fdk-aac", "Enable the Fraunhofer FDK AAC library"
  option "with-libvidstab", "Enable vid.stab support for video stabilization"
  option "with-x265", "Enable x265 encoder"
  option "with-libsoxr", "Enable the soxr resample library"
  option "with-webp", "Enable using libwebp to encode WEBP images"
  option "with-zeromq", "Enable using libzeromq to receive commands sent through a libzeromq client"
  option "with-snappy", "Enable Snappy library"
  option "with-rubberband", "Enable rubberband library"
  option "with-zimg", "Enable z.lib zimg library"
  option "with-openh264", "Enable OpenH264 library"
  option "with-xz", "Enable decoding of LZMA-compressed TIFF files"
  option "with-libebur128", "Enable using libebur128 for EBU R128 loudness measurement"

  depends_on "pkg-config" => :build

  # manpages won't be built without texi2html
  depends_on "texi2html" => :build
  depends_on "yasm" => :build

  depends_on "x264" => :recommended
  depends_on "lame" => :recommended
  depends_on "xvid" => :recommended

  depends_on "faac" => :optional
  depends_on "fontconfig" => :optional
  depends_on "freetype" => :optional
  depends_on "theora" => :optional
  depends_on "libvorbis" => :optional
  depends_on "libvpx" => :optional
  depends_on "rtmpdump" => :optional
  depends_on "opencore-amr" => :optional
  depends_on "libass" => :optional
  depends_on "openjpeg" => :optional
  depends_on "sdl" if build.with? "ffplay"
  depends_on "snappy" => :optional
  depends_on "speex" => :optional
  depends_on "schroedinger" => :optional
  depends_on "fdk-aac" => :optional
  depends_on "opus" => :optional
  depends_on "frei0r" => :optional
  depends_on "libcaca" => :optional
  depends_on "libbluray" => :optional
  depends_on "libsoxr" => :optional
  depends_on "libvidstab" => :optional
  depends_on "x265" => :optional
  depends_on "openssl" => :optional
  depends_on "libssh" => :optional
  depends_on "webp" => :optional
  depends_on "zeromq" => :optional
  depends_on "libbs2b" => :optional
  depends_on "rubberband" => :optional
  depends_on "zimg" => :optional
  depends_on "xz" => :optional
  depends_on "libebur128" => :optional

  depends_on "nasm" => :build if build.with? "openh264"

  # Remove when ffmpeg has support for openh264 1.6.0
  # See https://github.com/cisco/openh264/issues/2505
  resource "openh264-1.5.0" do
    url "https://github.com/cisco/openh264/archive/v1.5.0.tar.gz"
    sha256 "98077bd5d113c183ce02b678733b0cada2cf36750370579534c4d70f0b6c27b5"
  end

  def install
    args = %W[
      --prefix=#{prefix}
      --enable-shared
      --enable-pthreads
      --enable-gpl
      --enable-version3
      --enable-hardcoded-tables
      --enable-avresample
      --cc=#{ENV.cc}
      --host-cflags=#{ENV.cflags}
      --host-ldflags=#{ENV.ldflags}
    ]

    if build.with? "openh264"
      resource("openh264-1.5.0").stage do
        system "make", "install-shared", "PREFIX=#{libexec}/openh264-1.5.0"
        chmod 0444, libexec/"openh264-1.5.0/lib/libopenh264.dylib"
      end
      ENV.prepend_path "PKG_CONFIG_PATH", libexec/"openh264-1.5.0/lib/pkgconfig"
      args << "--enable-libopenh264"
    end

    args << "--enable-opencl" if MacOS.version > :lion

    args << "--enable-libx264" if build.with? "x264"
    args << "--enable-libmp3lame" if build.with? "lame"
    args << "--enable-libxvid" if build.with? "xvid"
    args << "--enable-libsnappy" if build.with? "snappy"

    args << "--enable-libfontconfig" if build.with? "fontconfig"
    args << "--enable-libfreetype" if build.with? "freetype"
    args << "--enable-libtheora" if build.with? "theora"
    args << "--enable-libvorbis" if build.with? "libvorbis"
    args << "--enable-libvpx" if build.with? "libvpx"
    args << "--enable-librtmp" if build.with? "rtmpdump"
    args << "--enable-libopencore-amrnb" << "--enable-libopencore-amrwb" if build.with? "opencore-amr"
    args << "--enable-libfaac" if build.with? "faac"
    args << "--enable-libass" if build.with? "libass"
    args << "--enable-ffplay" if build.with? "ffplay"
    args << "--enable-libssh" if build.with? "libssh"
    args << "--enable-libspeex" if build.with? "speex"
    args << "--enable-libschroedinger" if build.with? "schroedinger"
    args << "--enable-libfdk-aac" if build.with? "fdk-aac"
    args << "--enable-openssl" if build.with? "openssl"
    args << "--enable-libopus" if build.with? "opus"
    args << "--enable-frei0r" if build.with? "frei0r"
    args << "--enable-libcaca" if build.with? "libcaca"
    args << "--enable-libsoxr" if build.with? "libsoxr"
    args << "--enable-libvidstab" if build.with? "libvidstab"
    args << "--enable-libx265" if build.with? "x265"
    args << "--enable-libwebp" if build.with? "webp"
    args << "--enable-libzmq" if build.with? "zeromq"
    args << "--enable-libbs2b" if build.with? "libbs2b"
    args << "--enable-librubberband" if build.with? "rubberband"
    args << "--enable-libzimg" if build.with? "zimg"
    args << "--disable-indev=qtkit" if build.without? "qtkit"
    args << "--enable-libebur128" if build.with? "libebur128"

    if build.with? "xz"
      args << "--enable-lzma"
    else
      args << "--disable-lzma"
    end

    if build.with? "openjpeg"
      args << "--enable-libopenjpeg"
      args << "--disable-decoder=jpeg2000"
      args << "--extra-cflags=" + `pkg-config --cflags libopenjp2`.chomp
    end

    # These librares are GPL-incompatible, and require ffmpeg be built with
    # the "--enable-nonfree" flag, which produces unredistributable libraries
    if %w[faac fdk-aac openssl].any? { |f| build.with? f }
      args << "--enable-nonfree"
    end

    # A bug in a dispatch header on 10.10, included via CoreFoundation,
    # prevents GCC from building VDA support. GCC has no problems on
    # 10.9 and earlier.
    # See: https://github.com/Homebrew/homebrew/issues/33741
    if MacOS.version < :yosemite || ENV.compiler == :clang
      args << "--enable-vda"
    else
      args << "--disable-vda"
    end

    # For 32-bit compilation under gcc 4.2, see:
    # https://trac.macports.org/ticket/20938#comment:22
    ENV.append_to_cflags "-mdynamic-no-pic" if Hardware::CPU.is_32_bit? && Hardware::CPU.intel? && ENV.compiler == :clang

    system "./configure", *args

    if MacOS.prefer_64_bit?
      inreplace "config.mak" do |s|
        shflags = s.get_make_var "SHFLAGS"
        if shflags.gsub!(" -Wl,-read_only_relocs,suppress", "")
          s.change_make_var! "SHFLAGS", shflags
        end
      end
    end

    system "make", "install"

    if build.with? "tools"
      system "make", "alltools"
      bin.install Dir["tools/*"].select { |f| File.executable? f }
    end
  end

  def caveats
    if build.without? "faac" then <<-EOS.undent
      The native FFmpeg AAC encoder has been stable since FFmpeg 3.0. If you
      were using libvo-aacenc or libaacplus, both of which have been dropped in
      FFmpeg 3.0, please consider switching to the native encoder (-c:a aac),
      fdk-aac (-c:a libfdk_aac, ffmpeg needs to be installed with the
      --with-fdk-aac option), or faac (-c:a libfaac, ffmpeg needs to be
      installed with the --with-faac option).

      See the announcement
      https://ffmpeg.org/index.html#removing_external_aac_encoders for details,
      and https://trac.ffmpeg.org/wiki/Encode/AAC on best practices of encoding
      AAC with FFmpeg.
      EOS
    end
  end

  test do
    # Create an example mp4 file
    system "#{bin}/ffmpeg", "-y", "-filter_complex",
        "testsrc=rate=1:duration=1", "#{testpath}/video.mp4"
    assert (testpath/"video.mp4").exist?
  end
end