Add release notes for 12.
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Anton Khirnov
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Release Notes
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=============
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* 11 "One Louder"
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* 12 "Not Enough Trocadero"
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General notes
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-------------
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With this release we are trying to answer the numerous calls from our users for
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shorter development cycles. From now on we will aim for approximately two major
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releases per year.
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This release once again bumps the major versions of all the libraries, removing
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some long-deprecated APIs. This means that it is neither API nor ABI-compatible
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with the previous release. The users who still did not update their code are
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advised to look at the next section of these release notes, the doc/APIchanges
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file and the API migration guide on our wiki. If those are not sufficient, do
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not hesitate to contact us on IRC or through the user mailing list.
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Libav 11 is API-, but not ABI-compatible with the previous major release. This
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means that the code using our libraries needs to be rebuilt, but no source
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changes should be required. Note however, that a number of old APIs remain
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deprecated and will be dropped in the near future. All users are strongly
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encouraged to update their code as soon as possible. The doc/APIchanges file in
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the Libav source tree and the migration guide on the wiki should help with
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migration to the new APIs. If those are not sufficient, do not hesitate to
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contact us on IRC or through the user mailing list.
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Among the main highlights of this release are several additions related to
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hardware acceleration. There is a new API for managing hardware devices and
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frame pools, which allows to add new features such as zero-copy
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hardware-accelerated filtering with libavfilter and should reduce the
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boilerplate code required for existing hardware-accelerated decoders. We have
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added QuickSync decoding and encoding, NVENC encoding and CUDA image scaling,
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VAAPI encoding and image scaling, OpenMAX encoding, MMAL decoding and Direct3D11
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decoding.
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One specific API issue in libavformat deserves mentioning here. When using
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libavcodec for decoding or encoding and libavformat for demuxing or muxing,
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the standard practice was to use the stream codec context (AVStream.codec) for
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actual decoding or encoding. There are multiple problems with this pattern
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(the main one is that the decoder/demuxer or encoder/muxer are not necessarily
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synchronized and may overwrite each other's state), so it is now strongly
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discouraged and will likely be deprecated in the future. Users should instead
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allocate a separate decoding or encoding context and populate it from the
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demuxing codec context (or the reverse for encoding) with the
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avcodec_copy_context() function.
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The main highlights of this release include native Opus, VP7, OpenEXR, and On2
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AVC decoders, HEVC encoding through libx265, new APIs for exporting ReplayGain
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and display transformation metadata and countless bug fixes. A large effort was
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also expended on internal cleanups which are not very visible to our users,
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but should make the codebase cleaner, safer and easier to maintain and extend.
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One point worth mentioning is refactoring the large monolithic framework for
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architecture-specific codec optimizations into small blocks, which reduces the
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size of configurations that selectively enable or disable certain codecs.
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The avserver streaming tool, which has not been maintained for many years and
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was mostly broken, was removed from the tree. It was decided that it is a
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significant maintenance burden and that we do our users no service by pretending
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to support it, while we in fact do not.
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Other significant additions not related to hardware acceleration include
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decoders for Canopus HQ/HQA and HQX, Go2Meeting, AAC ELD, TDSC, Hap, DXV, SPV1,
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and a new ASF demuxer written according to the specification. There were also
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countless smaller changes and bug fixes.
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See the Changelog file for a more extensive list of significant changes.
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@ -54,22 +37,38 @@ have been deprecated and are scheduled for removal in the next release.
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Significant API changes include:
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[libavcodec]
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+ Added the avcodec_copy_context() function that must from now on be used for
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freeing codec contexts.
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+- Added a new VDA hardware acceleration API, since the old one was broken and
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not fixable in a compatible way. Deprecated the old VDA API.
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+ Added an object for storing codec parameters (AVCodecParameters) and its
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related API. It will now replace AVCodecContext everywhere except the actual
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encoders/decoders.
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+- Added a new API for handling refcounted AVPackets, mirroring the AVFrame API.
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Deprecated certain old ill-defined AVPacket functions.
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+- Added a new API for audio/video encoding and decoding, with decoupled input
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and output. This will e.g. allow a decoder to produce multiple output frames
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for a single input packet, which was not possible with the previous API. All
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users are strongly encouraged to switch to this new API as soon as possible,
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since certain decoders and encoders might start requiring the new API to be
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used.
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+- Added a new API for bitstream filtering, which works with refcounted
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AVPackets and is more clearly defined and documented. The old bitstream
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filtering API is now deprecated.
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[libavformat]
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+ Added support for exporting stream-global (as opposed to per-packet) side
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data. This feature is now used by some demuxers to export ReplayGain or
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display transformation matrix (aka rotation) or stereoscopic 3D mode.
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+ Added an API for live metadata updates through event flags.
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+- Changed the way to provide a hint about the desired timebase to muxers.
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Previously it was done by setting AVStream.codec.time_base. Now callers
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should set AVStream.time_base.
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+ Added new IO callbacks to AVFormatContext, allowing the caller to provide
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custom IO for certain special muxers and demuxers.
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+- Replaced AVStream.codec (AVCodecContext) with AVStream.codecpar
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(AVCodecParameters) as the means of signalling codec parameters between the
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muxers/demuxers and the caller.
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[libavresample]
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+ Added an API for working with AVFrames.
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[libavutil]
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+ Added a new API (hwcontext.h) for handling hardware acceleration devices and
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hardware frame pools.
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[libavfilter]
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+ Added a new struct, AVBufferSrcParameters, for passing the stream parameters
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to the buffer source. It is now the recommended way of configuring the buffer
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source.
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+ Added AVFilterContext.hw_device_ctx and AVFilterLink.hw_frames_ctx that allow
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hardware frames to be used in filter graphs.
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Please see the file doc/APIchanges for details along with similar
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programmer-centric information.
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