Resync to FFmpeg 2.3.1

 ┌───────────────────────────────────────────┐
 │ RELEASE NOTES for FFmpeg 2.3 "Mandelbrot" │
 └───────────────────────────────────────────┘

   The FFmpeg Project proudly presents FFmpeg 2.3 "Mandelbrot", a major
   release with all the great features committed during the three-month period
   since the release of FFmpeg 2.2.

   In this release, there are lots of internal overhauls that make FFmpeg a
   more accessible project for new developers. Many important new
   optimizations and features like QTKit and AVFoundation input devices are
   committed. Contributions done by Libav such as a new native Opus decoder
   are also merged.

   Because of the increasing difficulty to maintain and lack of maintainers,
   we are very sorry to say that we have removed all Blackfin and SPARC
   architecture assembly optimizations with the cleanups done. If you are
   interested in maintaining optimization for these two architecture, feel
   free to contact us and we will restore the code!

   Oh, and since this release, this modern-looking release note is provided in
   addition to the old-style Changelog file, to make it easier for you to
   focus on the most important features in this release.

   Enjoy!

   ┌────────────────────────────┐
   │ *  API Information         │
   └────────────────────────────┘

     FFmpeg 2.3 is completely source-compatible to the FFmpeg 2.2 series. There
     are however some API deprecations that you need to take care of. Use `git
     diff n2.2 n2.3 doc/APIchanges` to show the list of added and deprecated
     APIs. FFmpeg 2.3 includes the following library versions:

       • libavutil      52.92.100
       • libavcodec     55.69.100
       • libavformat    55.48.100
       • libavdevice    55.13.102
       • libavfilter     4.11.100
       • libswscale      2. 6.100
       • libswresample   0.19.100
       • libpostproc    52. 3.100

     Please refer to the doc/APIChanges file for more information.

   ┌────────────────────────────┐
   │ New Optimization           │
   └────────────────────────────┘

     We are excited to announce that we have committed new x86 assembly
     optimization for HEVC, and FFmpeg's audio resampler libswresample. ARM
     users will get a boost in MLP/TrueHD decoding thanks to new optimization.
     Decoding Huffyuv also got a major boost from optimization on the C code.

     Of special interest for Microsoft Visual Studio users, we have also
     converted some preexisting x86 assembly to NASM/Yasm format compatible
     with MSVC setup, especially in the area of audio resampling.

     Another major feature in this release is the introduction of AArch64
     (ARMv8) assembly optimization. AArch64 is another name for the first
     64-bit ARM architecture, used by Apple A7 SoC inside iPhone 5S. Some
     32-bit ARM assembly has already been ported to AArch64, but more work is
     underway.

   ┌────────────────────────────┐
   │ Native Opus decoder        │
   └────────────────────────────┘

     Opus is an open audio format jointly developed by Xiph.Org, Mozilla,
     Skype/Microsoft, and Broadcom. It combines the features of the Skype Cilk
     speech codec and the Xiph.Org CELT music codec into one low-latency
     codec. Decoding Opus is already possible since FFmpeg 1.0 using the
     libopus library, but the new Opus native decoder brings a higher level of
     stability and speed.

   ┌────────────────────────────┐
   │ QTKit and AVFoundation     │
   └────────────────────────────┘

     For OS X users, the new QTKit and AVFoundation devices allow you to use
     the integrated camera on Macs. AVFoundation is a newer API only available
     on OS X 10.7 "Lion" or newer. For users with older OS X systems, the
     QTKit device using the older OS X API is for you.

   ┌────────────────────────────┐
   │ API Additions              │
   └────────────────────────────┘

     In this release, stream side data are introduced as AVStream.side_data as
     a way to store miscellaneous stream-wide information. The format is
     similar to the previously anonymous structure AVPacket.side_data (now
     named as AVPacketSideData). With this change, audio ReplayGain
     information and video rotation matrix are now exported through this API,
     if available in the demuxer.

     We also have improved libswresample's Doxygen API documentation, so new
     developers wishing to use FFmpeg's excellent libraries can get started
     more easily and faster.

   ┌────────────────────────────┐
   │ Last But Not Least         │
   └────────────────────────────┘

     Other interesting new features including hqx video filter, a pixel art
     scaling filter; a fixed-point AC-3 decoder contributed by Imagination
     Technologies; an On2 TrueMotion VP7 video decoder; an HTML5 WebVTT
     subtitle encoder that allows creation of WebVTT from any text-based
     subtitles; and an 1-bit Direct Stream Digital audio decoder.

 ┌────────────────────────────┐
 │ ★  List of New Features    │
 └────────────────────────────┘

   ┌────────────────────────────┐
   │ Command line tools         │
   └────────────────────────────┘

    • Support for decoding through DXVA2 in ffmpeg

   ┌────────────────────────────┐
   │ libavcodec                 │
   └────────────────────────────┘

    • AC3 fixed-point decoding
    • VP7 video decoder
    • Alias PIX image encoder and decoder
    • Improvements to the BRender PIX image decoder
    • Improvements to the XBM decoder
    • Improvements to OpenEXR image decoder
    • Support decoding 16-bit RLE SGI images
    • Direct Stream Digital (DSD) decoder
    • On2 AVC (Audio for Video) decoder
    • Native Opus decoder
    • WebVTT encoder

   ┌────────────────────────────┐
   │ libavdevice                │
   └────────────────────────────┘

    • QTKit input device
    • GDI screen grabbing for Windows
    • AVFoundation input device

   ┌────────────────────────────┐
   │ libavformat                │
   └────────────────────────────┘

    • subfile protocol
    • Phantom Cine demuxer
    • Alternative rendition support for HTTP Live Streaming
    • Magic Lantern Video (MLV) demuxer
    • Image format auto-detection
    • LRC lyric file demuxer and muxer
    • Samba protocol (via libsmbclient)
    • WebM DASH Manifest muxer

   ┌────────────────────────────┐
   │ libavfilter                │
   └────────────────────────────┘

    • shuffleplanes filter
    • libbs2b-based stereo-to-binaural audio filter
    • showcqt multimedia filter
    • zoompan filter
    • signalstats filter
    • hqx filter (hq2x, hq3x, hq4x)
    • flanger filter
    • libfribidi support in drawtext

 ┌────────────────────────────┐
 │ ⚠  Behaviour changes       │
 └────────────────────────────┘

  • libx264 reference frames count is now limited depending on level chosen
  • Because of the new image format auto-detection feature, you don't need to
    specify image format when decoding an image with no extension.