WebM Codec SDK

CHANGELOG

    2026-01-06 v1.16.0 "Xenonetta Duck"
      This release includes Arm SVE2 and Neon optimizations for 12-tap filters,
      AVX512 implementations for SAD, support for per-frame and per-spatial-layer
      PSNR calculation, and numerous bug fixes.

      - Upgrading:
        This release is ABI incompatible with the previous release.

        Unit tests require C++17 to build.

        Support for 32-bit iOS targets (armv7, armv7s, and i386) has been removed.

      - Enhancement:
        Optimized Arm SVE2 and Neon implementations for 12-tap convolution filters.
        Optimized Neon High Bitdepth (HBD) SAD and sad_avg functions.
        Added Arm Neon DotProd and I8MM implementations for vpx_convolve12.
        Added AVX512 implementations for SAD64 and sad_skip functions.
        Added SSSE3 and AVX2 implementations for 12-tap temporal filter prediction.
        Added support for per-frame and per-spatial-layer PSNR calculation.

        Adjusted temporal filter strength to improve visual quality and reduce block
        artifacts.

        Added support for darwin24 (macOS 15) and darwin25 (macOS 26).
        libwebm is upgraded to commit b4f01ea.

      - Bug fixes:
        Fix to heap buffer overflow in vp9_deblock, vp9_post_proc_frame, and
        vp9_pack_bitstream.

        Fix to integer overflow in vp9_highbd_post_proc, vp9_rc_regulate_q,
        tiny_ssim, and vp9_calc_pframe_target_size_one_pass_cbr.

        Fix to use-of-uninitialized-value in vp9_highbd_post_proc, mfqe, and
        vp8_datarate_test.

        Fix to out-of-bounds in log_tile_cols_from_picsize_level.
        Fix to double free on initialization failure in vpx_codec_enc_init_multi.
        Fix to division-by-zero crash in vpxenc with 0 FPS numerator input.

        Fix to various build failures for Arm/SVE2, macOS cross-compilation, and
        Xcode 16.

    2025-05-28 v1.15.2 "Wigeon Duck"
      This release fixes CVE-2025-5283 (bug webm:413411335), and is ABI compatible
      with the previous release.

    2025-01-09 v1.15.1 "Wigeon Duck"
      This release bumps up the SO major version and fixes the language about ABI
      compatibility in the previous release changelog.

    2024-10-22 v1.15.0 "Wigeon Duck"
      This release includes new codec control for key frame filtering, more Neon
      optimizations, improvements to RTC encoding and bug fixes.

      - Upgrading:
        This release is ABI incompatible with the previous release.

        It is strongly recommended to skip this release and upgrade to v1.15.1 since
        the shared object was versioned incorrectly, as shown in
        https://issues.webmproject.org/issues/384672478.

        Temporal filtering improvement that can be turned on with the new codec
        control VP9E_SET_KEY_FRAME_FILTERING, which gives 1+% BD-rate saving with
        minimal encoder time increase.

        libwebm is upgraded to libwebm-1.0.0.31-10-g3b63004

      - Enhancement:
        Neon optimization speed up
          1-3% speed up across speed 5 to 10 for RTC
          3% speed up for speed 0 and 1 for VoD in standard bitdepth
          3% and 7% speed up for speed 0 and 1 respectively for VoD in high bitdepth
        Scene detection is allowed for all RTC speeds (>=5)
        Support profile guided optimizations

        Delta quantization parameters for UV channels for vp8 is supported in RTC
        rate control library

        Rate control parameters are reset and maximum QP is enforced on scene
        changes in SVC when there is no inter-layer prediction

      - Bug fixes:
        Fix to Uninitialized scalar variable in `vp9_rd_pick_inter_mode_sb()`
        Fix to Integer-overflow in `resize_multistep`
        Fix to Heap-buffer-overflow in `vpx_sad64x64_avx2`
        Fix to Crash in `vpx_sad8x8_sse2`
        Fix to Assertion in `write_modes`
        Support profile guided optimizations
        Fix to Integer-overflow in `encode_frame_to_data_rate`
        Fix to Integer-overflow in `vp9_svc_check_reset_layer_rc_flag`
        Fix to core dump error from /usr/bin/tools/tiny_ssim --help
        Fix to use-of-uninitialized-value in `vp9_setup_tpl_stats`
        Fix to Undefined-shift in `vp9_cyclic_refresh_setup`
        Fix to redundant `&& __GNUC__` preproc check
        Fix to valgrind warning in EncodeAPI.OssFuzz69906
        Fix to Index-out-of-bounds in `vp8_rd_pick_inter_mode`
        Fix to Integer-overflow in `vp8_pick_frame_size`
        Fix to Use-of-uninitialized-value in `vpx_codec_peek_stream_info`
        Fix to log clutters with the message "Warning: Desired height too large"
        Fix to Integer-overflow in `vp9_svc_adjust_avg_frame_qindex`

        Fix to integer overflows caused by huge target bitrate, frame rate, or
        g_timebase numerator or denominator

        Fix to missing license headers
        Fix to build failure for Android Armv7
        Fix to integer overflows in image helpers
        Fix to Integer-overflow in `vp9_calc_iframe_target_size_one_pass_cbr`
        Fix to Heap-buffer-overflow in `vp9_pick_inter_mode`
        Fix to Segv in `vp9_multi_thread_tile_init`
        Fix to Use-of-uninitialized-value in `vp9_row_mt_sync_mem_dealloc`
        Fix to Crash in `mbloop_filter_vertical_edge_c`
        Fix to Check failed in CheckUnwind
        Fix to Heap-buffer-overflow in `write_modes_b` and `vpx_write`
        Fix to Possible signed integer overflow found in `vpx_codec_encode`
        Fix to build conflicts between Abseil and libaom/libvpx in Win ARM64 builds
        Fix to build failures on aarch64
        Fix to Data race in libvpx ARM NEON
        Fix to Heap-buffer-overflow in `scale_plane_1_to_2_phase_0`
        Fix to integer overflow in `encode_mb_row`
        Fix to Floating-point-exception in `vp8_pick_frame_size`
        Fix to Heap-buffer-overflow in `vp9_enc_setup_mi`
        Fix to build failure with --target=arm64-win64-vs17
        Fix to heap-buffer-overflow write in `vpx_img_read()`
        Fix to C vs armv8-linux-gcc encode mismatches for `y4m_360p_10bit_input`
        Fix to Null-dereference READ in `ml_predict_var_rd_partitioning`
        Fix to Heap-buffer-overflow in `vpx_scaled_2d_ssse3`
        Fix to Crash in `convolve_horiz`
        Fix to Ill in `vpx_scaled_2d_ssse3`
        Fix to Global-buffer-overflow in `cost_coeffs`

    2024-05-21 v1.14.1 "Venetian Duck"
      This release includes enhancements and bug fixes.

      - Upgrading:
        This release is ABI compatible with the previous release.

      - Enhancement:
        Improved the detection of compiler support for AArch64 extensions,
        particularly SVE.

        Added vpx_codec_get_global_headers() support for VP9.

      - Bug fixes:
        Added buffer bounds checks to vpx_writer and vpx_write_bit_buffer.
        Fix to GetSegmentationData() crash in aq_mode=0 for RTC rate control.
        Fix to alloc for row_base_thresh_freq_fac.
        Free row mt memory before freeing cpi->tile_data.
        Fix to buffer alloc for vp9_bitstream_worker_data.
        Fix to VP8 race issue for multi-thread with pnsr_calc.
        Fix to uv width/height in vp9_scale_and_extend_frame_ssse3.
        Fix to integer division by zero and overflow in calc_pframe_target_size().
        Fix to integer overflow in vpx_img_alloc() & vpx_img_wrap()(CVE-2024-5197).
        Fix to UBSan error in vp9_rc_update_framerate().
        Fix to UBSan errors in vp8_new_framerate().
        Fix to integer overflow in vp8 encodeframe.c.
        Handle EINTR from sem_wait().

    2024-01-02 v1.14.0 "Venetian Duck"
      This release drops support for old C compilers, such as Visual Studio 2012
      and older, that disallow mixing variable declarations and statements (a C99
      feature). It adds support for run-time CPU feature detection for Arm
      platforms, as well as support for darwin23 (macOS 14).

      - Upgrading:
        This release is ABI incompatible with the previous release.

        Various new features for rate control library for real-time: SVC parallel
        encoding, loopfilter level, support for frame dropping, and screen content.

        New callback function send_tpl_gop_stats for vp9 external rate control
        library, which can be used to transmit TPL stats for a group of pictures. A
        public header vpx_tpl.h is added for the definition of TPL stats used in
        this callback.

        libwebm is upgraded to libwebm-1.0.0.29-9-g1930e3c.

      - Enhancement:
        Improvements on Neon optimizations: VoD: 12-35% speed up for bitdepth 8,
        68%-151% speed up for high bitdepth.

        Improvements on AVX2 and SSE optimizations.
        Improvements on LSX optimizations for LoongArch.
        42-49% speedup on speed 0 VoD encoding.
        Android API level predicates.

      - Bug fixes:
        Fix to missing prototypes from the rtcd header.
        Fix to segfault when total size is enlarged but width is smaller.
        Fix to the build for arm64ec using MSVC.
        Fix to copy BLOCK_8X8's mi to PICK_MODE_CONTEXT::mic.
        Fix to -Wshadow warnings.
        Fix to heap overflow in vpx_get4x4sse_cs_neon.
        Fix to buffer overrun in highbd Neon subpel variance filters.
        Added bitexact encode test script.
        Fix to -Wl,-z,defs with Clang's sanitizers.
        Fix to decoder stability after error & continued decoding.
        Fix to mismatch of VP9 encode with NEON intrinsics with C only version.
        Fix to Arm64 MSVC compile vpx_highbd_fdct4x4_neon.
        Fix to fragments count before use.
        Fix to a case where target bandwidth is 0 for SVC.
        Fix mask in vp9_quantize_avx2,highbd_get_max_lane_eob.
        Fix to int overflow in vp9_calc_pframe_target_size_one_pass_cbr.
        Fix to integer overflow in vp8,ratectrl.c.
        Fix to integer overflow in vp9 svc.
        Fix to avg_frame_bandwidth overflow.
        Fix to per frame qp for temporal layers.
        Fix to unsigned integer overflow in sse computation.
        Fix to uninitialized mesh feature for BEST mode.
        Fix to overflow in highbd temporal_filter.
        Fix to unaligned loads w/w==4 in vpx_convolve_copy_neon.
        Skip arm64_neon.h workaround w/VS >= 2019.
        Fix to c vs avx mismatch of diamond_search_sad().
        Fix to c vs intrinsic mismatch of vpx_hadamard_32x32() function.
        Fix to a bug in vpx_hadamard_32x32_neon().
        Fix to Clang -Wunreachable-code-aggressive warnings.
        Fix to a bug in vpx_highbd_hadamard_32x32_neon().
        Fix to -Wunreachable-code in mfqe_partition.
        Force mode search on 64x64 if no mode is selected.
        Fix to ubsan failure caused by left shift of negative.
        Fix to integer overflow in calc_pframe_target_size.
        Fix to float-cast-overflow in vp8_change_config().
        Fix to a null ptr before use.
        Conditionally skip using inter frames in speed features.
        Remove invalid reference frames.
        Disable intra mode search speed features conditionally.
        Set nonrd keyframe under dynamic change of deadline for rtc.
        Fix to scaled reference offsets.
        Set skip_recode=0 in nonrd_pick_sb_modes.
        Fix to an edge case when downsizing to one.
        Fix to a bug in frame scaling.
        Fix to pred buffer stride.
        Fix to a bug in simple motion search.
        Update frame size in actual encoding.

    2023-09-29 v1.13.1 "Ugly Duckling"
      This release contains two security related fixes. One each for VP8 and VP9.

      - Upgrading:
        This release is ABI compatible with the previous release.

      - Bug fixes:
        https://crbug.com/1486441 (CVE-2023-5217)
        Fix to a crash related to VP9 encoding (#1642, CVE-2023-6349)

    2023-01-31 v1.13.0 "Ugly Duckling"
      This release includes more Neon and AVX2 optimizations, adds a new codec
      control to set per frame QP, upgrades GoogleTest to v1.12.1, and includes
      numerous bug fixes.

      - Upgrading:
        This release is ABI incompatible with the previous release.

        New codec control VP9E_SET_QUANTIZER_ONE_PASS to set per frame QP.

        GoogleTest is upgraded to v1.12.1.

        .clang-format is upgraded to clang-format-11.

        VPX_EXT_RATECTRL_ABI_VERSION was bumped due to incompatible changes to the
        feature of using external rate control models for vp9.

      - Enhancement:
        Numerous improvements on Neon optimizations.
        Numerous improvements on AVX2 optimizations.
        Additional ARM targets added for Visual Studio.

      - Bug fixes:
        Fix to calculating internal stats when frame dropped.
        Fix to segfault for external resize test in vp9.
        Fix to build system with replacing egrep with grep -E.
        Fix to a few bugs with external RTC rate control library.
        Fix to make SVC work with VBR.
        Fix to key frame setting in VP9 external RC.
        Fix to -Wimplicit-int (Clang 16).
        Fix to VP8 external RC for buffer levels.
        Fix to VP8 external RC for dynamic update of layers.
        Fix to VP9 auto level.
        Fix to off-by-one error of max w/h in validate_config.
        Fix to make SVC work for Profile 1.

    2022-06-17 v1.12.0 "Torrent Duck"
      This release adds optimizations for Loongarch, adds support for vp8 in the
      real-time rate control library, upgrades GoogleTest to v1.11.0, updates
      libwebm to libwebm-1.0.0.28-20-g206d268, and includes numerous bug fixes.

      - Upgrading:
        This release is ABI compatible with the previous release.

        vp8 support in the real-time rate control library.
        New codec control VP8E_SET_RTC_EXTERNAL_RATECTRL is added.

        Configure support for darwin21 is added.

        GoogleTest is upgraded to v1.11.0.

        libwebm is updated to libwebm-1.0.0.28-20-g206d268.

        Allow SimpleEncode environment to take target level as input to match
        the level conformance in vp9.

      - Enhancement:
        Numerous improvements on checking memory allocations.
        Optimizations for Loongarch.
        Code clean-up.

      - Bug fixes:
        Fix to a crash related to {vp8/vp9}_set_roi_map.
        Fix to compiling failure with -Wformat-nonliteral.
        Fix to integer overflow with vp9 with high resolution content.
        Fix to AddNoiseTest failure with ARMv7.
        Fix to libvpx Null-dereference READ in vp8.

    2021-09-27 v1.11.0 "Smew Duck"
      This maintenance release adds support for VBR mode in VP9 rate control
      interface, new codec controls to get quantization parameters and loop filter
      levels, and includes several improvements to NEON and numerous bug fixes.

      - Upgrading:
        This release is ABI incompatible with the previous release.
        New codec control is added to get quantization parameters and loop filter
        levels.

        VBR mode is supported in VP9 rate control library.

      - Enhancement:
        Numerous improvements for Neon optimizations.
        Code clean-up and refactoring.
        Calculation of rd multiplier is changed with BDRATE gains.

      - Bug fixes:
        Fix to overflow on duration.
        Fix to several instances of -Wunused-but-set-variable.
        Fix to avoid chroma resampling for 420mpeg2 input.
        Fix to overflow in calc_iframe_target_size.
        Fix to disallow skipping transform and quantization.
        Fix some -Wsign-compare warnings in simple_encode.
        Fix input file path in simple_encode_test.
        Fix valid range for under/over_shoot pct.

    2021-03-09 v1.10.0 "Ruddy Duck"
      This maintenance release adds support for darwin20 and new codec controls, as
      well as numerous bug fixes.

      - Upgrading:
        This release is ABI incompatible with the previous release.
        New codec control is added to disable loopfilter for VP9.

        New encoder control is added to disable feature to increase Q on overshoot
        detection for CBR.

        Configure support for darwin20 is added.

        New codec control is added for VP9 rate control. The control ID of this
        interface is VP9E_SET_EXTERNAL_RATE_CONTROL. To make VP9 use a customized
        external rate control model, users will have to implement each callback
        function in vpx_rc_funcs_t and register them using libvpx API
        vpx_codec_control_() with the control ID.

      - Enhancement:
        Use -std=gnu++11 instead of -std=c++11 for c++ files.

      - Bug fixes:
        Override assembler with --as option of configure for MSVS.
        Fix several compilation issues with gcc 4.8.5.
        Fix to resetting rate control for temporal layers.
        Fix to the rate control stats of SVC example encoder when number of spatial
        layers is 1.
        Fix to reusing motion vectors from the base spatial layer in SVC.
        2 pass related flags removed from SVC example encoder.

    2020-07-29 v1.9.0 "Quacking Duck"
      This release adds support for NV12, a separate library for rate control, as
      well as incremental improvements.

      - Upgrading:
        This release is ABI compatible with the previous release.
        NV12 support is added to this release.
        A new interface is added for VP9 rate control. The new library libvp9rc.a
        must be linked by applications.
        Googletest is updated to v1.10.0.
        simple_encode.cc is compiled into a new library libsimple_encode.a with
        CONFIG_RATE_CTRL.

      - Enhancement:
        Various changes to improve VP9 SVC, rate control, quality and speed to real
        time encoding.

      - Bug fixes:
        Fix key frame update refresh simulcast flexible svc.
        Fix to disable_16x16part speed feature for real time encoding.
        Fix some signed integer overflows for VP9 rate control.
        Fix initialization of delta_q_uv.
        Fix condition in regulate_q for cyclic refresh.
        Various fixes to dynamic resizing for VP9 SVC.

    2019-12-09 v1.8.2 "Pekin Duck"
      This release collects incremental improvements to many aspects of the library.

      - Upgrading:
        This release is ABI compatible with the previous release.
        ARCH_* defines have been removed in favor of VPX_ARCH_*.

    2019-07-15 v1.8.1 "Orpington Duck"
      This release collects incremental improvements to many aspects of the library.

      - Upgrading:
        This release is ABI incompatible with the previous release.
        VP8E_SET_CPUUSED now accepts values up to 9 for vp9.
        VPX_CTRL_VP9E_SET_MAX_INTER_BITRATE_PCT had a spelling fix (was VP8E).
        The --sdk-path option has been removed. If you were using it to build for
          Android please read build/make/Android.mk for alternatives.
        All PPC optimizations have been disabled:
          https://bugs.chromium.org/p/webm/issues/detail?id=1522.

      - Enhancements:
        Various changes to improve encoder rate control, quality and speed
          for practically every use case.

      - Bug fixes:
        vp9-rtc: Fix color artifacts for speed >= 8.

    2019-01-31 v1.8.0 "Northern Shoveler Duck"
      This release focused on encoding performance for realtime and VOD use cases.

      - Upgrading:
        This release is ABI incompatible with the previous release. This adds and
        improves several vp9 controls. Most are related to SVC:
          VP9E_SET_SVC_FRAME_DROP_LAYER:
            - Frame dropping in SVC.
          VP9E_SET_SVC_INTER_LAYER_PRED:
            - Inter-layer prediction in SVC.
          VP9E_SET_SVC_GF_TEMPORAL_REF:
            - Enable long term temporal reference in SVC.
          VP9E_SET_SVC_REF_FRAME_CONFIG/VP9E_GET_SVC_REF_FRAME_CONFIG:
            - Extend and improve this control for better flexibility in setting SVC
              pattern dynamically.
          VP9E_SET_POSTENCODE_DROP:
            - Allow for post-encode frame dropping (applies to non-SVC too).
          VP9E_SET_SVC_SPATIAL_LAYER_SYNC:
            - Enable spatial layer sync frames.
          VP9E_SET_SVC_LAYER_ID:
            - Extend api to specify temporal id for each spatial layers.
          VP9E_SET_ROI_MAP:
            - Extend Region of Interest functionality to VP9.

      - Enhancements:
        2 pass vp9 encoding has improved substantially. When using --auto-alt-ref=6,
        we see approximately 8% for VBR and 10% for CQ. When using --auto-alt-ref=1,
        the gains are approximately 4% for VBR and 5% for CQ.

        For real-time encoding, speed 7 has improved by ~5-10%. Encodes targeted at
        screen sharing have improved when the content changes significantly (slide
        sharing) or scrolls. There is a new speed 9 setting for mobile devices which
        is about 10-20% faster than speed 8.

      - Bug fixes:
        VP9 denoiser issue.
        VP9 partition issue for 1080p.
        VP9 rate control improvments.
        Postprocessing Multi Frame Quality Enhancement (MFQE) issue.
        VP8 multithread decoder issues.
        A variety of fuzzing issues.

    2018-01-04 v1.7.0 "Mandarin Duck"
      This release focused on high bit depth performance (10/12 bit) and vp9
      encoding improvements.

      - Upgrading:
        This release is ABI incompatible due to new vp9 encoder features.

        Frame parallel decoding for vp9 has been removed.

      - Enhancements:
        vp9 encoding supports additional threads with --row-mt. This can be greater
        than the number of tiles.

        Two new vp9 encoder options have been added:
          --corpus-complexity
          --tune-content=film

        Additional tooling for respecting the vp9 "level" profiles has been added.

      - Bug fixes:
        A variety of fuzzing issues.
        vp8 threading fix for ARM.
        Codec control VP9_SET_SKIP_LOOP_FILTER fixed.
        Reject invalid multi resolution configurations.

    2017-01-09 v1.6.1 "Long Tailed Duck"
      This release improves upon the VP9 encoder and speeds up the encoding and
      decoding processes.

      - Upgrading:
        This release is ABI compatible with 1.6.0.

      - Enhancements:
        Faster VP9 encoding and decoding.
        High bit depth builds now provide similar speed for 8 bit encode and decode
        for x86 targets. Other platforms and higher bit depth improvements are in
        progress.

      - Bug Fixes:
        A variety of fuzzing issues.

    2016-07-20 v1.6.0 "Khaki Campbell Duck"
      This release improves upon the VP9 encoder and speeds up the encoding and
      decoding processes.

      - Upgrading:
        This release is ABI incompatible with 1.5.0 due to a new 'color_range' enum
        in vpx_image and some minor changes to the VP8_COMP structure.

        The default key frame interval for VP9 has changed from 128 to 9999.

      - Enhancement:
        A core focus has been performance for low end Intel processors. SSSE3
        instructions such as 'pshufb' have been avoided and instructions have been
        reordered to better accommodate the more constrained pipelines.

        As a result, devices based on Celeron processors have seen substantial
        decoding improvements. From Indian Runner Duck to Javan Whistling Duck,
        decoding speed improved between 10 and 30%. Between Javan Whistling Duck
        and Khaki Campbell Duck, it improved another 10 to 15%.

        While Celeron benefited most, Core-i5 also improved 5% and 10% between the
        respective releases.

        Realtime performance for WebRTC for both speed and quality has received a
        lot of attention.

      - Bug Fixes:
        A number of fuzzing issues, found variously by Mozilla, Chromium and others,
        have been fixed and we strongly recommend updating.

    2015-11-09 v1.5.0 "Javan Whistling Duck"
      This release improves upon the VP9 encoder and speeds up the encoding and
      decoding processes.

      - Upgrading:
        This release is ABI incompatible with 1.4.0. It drops deprecated VP8
        controls and adds a variety of VP9 controls for testing.

        The vpxenc utility now prefers VP9 by default.

      - Enhancements:
        Faster VP9 encoding and decoding
        Smaller library size by combining functions used by VP8 and VP9

      - Bug Fixes:
        A variety of fuzzing issues

    2015-04-03 v1.4.0 "Indian Runner Duck"
      This release includes significant improvements to the VP9 codec.

      - Upgrading:
        This release is ABI incompatible with 1.3.0. It drops the compatibility
        layer, requiring VPX_IMG_FMT_* instead of IMG_FMT_*, and adds several codec
        controls for VP9.

      - Enhancements:
        Faster VP9 encoding and decoding
        Multithreaded VP9 decoding (tile and frame-based)
        Multithreaded VP9 encoding - on by default
        YUV 4:2:2 and 4:4:4 support in VP9
        10 and 12bit support in VP9
        64bit ARM support by replacing ARM assembly with intrinsics

      - Bug Fixes:
        Fixes a VP9 bitstream issue in Profile 1. This only affected non-YUV 4:2:0
        files.

      - Known Issues:
        Frame Parallel decoding fails for segmented and non-420 files.

    2013-11-15 v1.3.0 "Forest"
      This release introduces the VP9 codec in a backward-compatible way.
      All existing users of VP8 can continue to use the library without
      modification. However, some VP8 options do not map to VP9 in the same manner.

      The VP9 encoder in this release is not feature complete. Users interested in
      the encoder are advised to use the git master branch and discuss issues on
      libvpx mailing lists.

      - Upgrading:
        This release is ABI and API compatible with Duclair (v1.0.0). Users
        of older releases should refer to the Upgrading notes in this document
        for that release.

      - Enhancements:
          Get rid of bashisms in the main build scripts
          Added usage info on command line options
          Add lossless compression mode
          Dll build of libvpx
          Add additional Mac OS X targets: 10.7, 10.8 and 10.9 (darwin11-13)
          Add option to disable documentation
          configure: add --enable-external-build support
          make: support V=1 as short form of verbose=yes
          configure: support mingw-w64
          configure: support hardfloat armv7 CHOSTS
          configure: add support for android x86
          Add estimated completion time to vpxenc
          Don't exit on decode errors in vpxenc
          vpxenc: support scaling prior to encoding
          vpxdec: support scaling output
          vpxenc: improve progress indicators with --skip
          msvs: Don't link to winmm.lib
          Add a new script for producing vcxproj files
          Produce Visual Studio 10 and 11 project files
          Produce Windows Phone project files
          msvs-build: use msbuild for vs >= 2005
          configure: default configure log to config.log
          Add encoding option --static-thresh

      - Speed:
          Miscellaneous speed optimizations for VP8 and VP9.

      - Quality:
          In general, quality is consistent with the Eider release.

      - Bug Fixes:
          This release represents approximately a year of engineering effort,
          and contains multiple bug fixes. Please refer to git history for details.

    2012-12-21 v1.2.0
      This release acts as a checkpoint for a large amount of internal refactoring
      and testing. It also contains a number of small bugfixes, so all users are
      encouraged to upgrade.

      - Upgrading:
        This release is ABI and API compatible with Duclair (v1.0.0). Users
        of older releases should refer to the Upgrading notes in this
        document for that release.

      - Enhancements:
          VP8 optimizations for MIPS dspr2
          vpxenc: add -quiet option

      - Speed:
          Encoder and decoder speed is consistent with the Eider release.

      - Quality:
          In general, quality is consistent with the Eider release.

          Minor tweaks to ARNR filtering
          Minor improvements to real time encoding with multiple temporal layers

      - Bug Fixes:
          Fixes multithreaded encoder race condition in loopfilter
          Fixes multi-resolution threaded encoding
          Fix potential encoder dead-lock after picture resize

    2012-05-09 v1.1.0 "Eider"
      This introduces a number of enhancements, mostly focused on real-time
      encoding. In addition, it fixes a decoder bug (first introduced in
      Duclair) so all users of that release are encouraged to upgrade.

      - Upgrading:
        This release is ABI and API compatible with Duclair (v1.0.0). Users
        of older releases should refer to the Upgrading notes in this
        document for that release.

        This release introduces a new temporal denoiser, controlled by the
        VP8E_SET_NOISE_SENSITIVITY control. The temporal denoiser does not
        currently take a strength parameter, so the control is effectively
        a boolean - zero (off) or non-zero (on). For compatibility with
        existing applications, the values accepted are the same as those
        for the spatial denoiser (0-6). The temporal denoiser is enabled
        by default, and the older spatial denoiser may be restored by
        configuring with --disable-temporal-denoising. The temporal denoiser
        is more computationally intensive than the spatial one.

        This release removes support for a legacy, decode only API that was
        supported, but deprecated, at the initial release of libvpx
        (v0.9.0). This is not expected to have any impact. If you are
        impacted, you can apply a reversion to commit 2bf8fb58 locally.
        Please update to the latest libvpx API if you are affected.

      - Enhancements:
          Adds a motion compensated temporal denoiser to the encoder, which
          gives higher quality than the older spatial denoiser. (See above
          for notes on upgrading).

          In addition, support for new compilers and platforms were added,
          including:
            improved support for XCode
            Android x86 NDK build
            OS/2 support
            SunCC support

          Changing resolution with vpx_codec_enc_config_set() is now
          supported. Previously, reinitializing the codec was required to
          change the input resolution.

          The vpxenc application has initial support for producing multiple
          encodes from the same input in one call. Resizing is not yet
          supported, but varying other codec parameters is. Use -- to
          delineate output streams. Options persist from one stream to the
          next.

          Also, the vpxenc application will now use a keyframe interval of
          5 seconds by default. Use the --kf-max-dist option to override.

      - Speed:
          Decoder performance improved 2.5% versus Duclair. Encoder speed is
          consistent with Duclair for most material. Two pass encoding of
          slideshow-like material will see significant improvements.

          Large realtime encoding speed gains at a small quality expense are
          possible by configuring the on-the-fly bitpacking experiment with
          --enable-onthefly-bitpacking. Realtime encoder can be up to 13%
          faster (ARM) depending on the number of threads and bitrate
          settings. This technique sees constant gain over the 5-16 speed
          range. For VC style input the loss seen is up to 0.2dB. See commit
          52cf4dca for further details.

      - Quality:
          On the whole, quality is consistent with the Duclair release. Some
          tweaks:

            Reduced blockiness in easy sections by applying a penalty to
            intra modes.

            Improved quality of static sections (like slideshows) with
            two pass encoding.

            Improved keyframe sizing with multiple temporal layers

      - Bug Fixes:
          Corrected alt-ref contribution to frame rate for visible updates
          to the alt-ref buffer. This affected applications making manual
          usage of the frame reference flags, or temporal layers.

          Additional constraints were added to disable multi-frame quality
          enhancement (MFQE) in sections of the frame where there is motion.
          (#392)

          Fixed corruption issues when vpx_codec_enc_config_set() was called
          with spatial resampling enabled.

          Fixed a decoder error introduced in Duclair where the segmentation
          map was not being reinitialized on keyframes (#378)

    2012-01-27 v1.0.0 "Duclair"
      Our fourth named release, focused on performance and features related to
      real-time encoding. It also fixes a decoder crash bug introduced in
      v0.9.7, so all users of that release are encouraged to upgrade.

      - Upgrading:
          This release is ABI incompatible with prior releases of libvpx, so the
          "major" version number has been bumped to 1. You must recompile your
          applications against the latest version of the libvpx headers. The
          API remains compatible, and this should not require code changes in most
          applications.

      - Enhancements:
          This release introduces several substantial new features to the encoder,
          of particular interest to real time streaming applications.

          Temporal scalability allows the encoder to produce a stream that can
          be decimated to different frame rates, with independent rate targeting
          for each substream.

          Multiframe quality enhancement postprocessing can make visual quality
          more consistent in the presence of frames that are substantially
          different quality than the surrounding frames, as in the temporal
          scalability case and in some forced keyframe scenarios.

          Multiple-resolution encoding support allows the encoding of the
          same content at different resolutions faster than encoding them
          separately.

      - Speed:
          Optimization targets for this release included the decoder and the real-
          time modes of the encoder. Decoder speed on x86 has improved 10.5% with
          this release. Encoder improvements followed a curve where speeds 1-3
          improved 4.0%-1.5%, speeds 4-8 improved <1%, and speeds 9-16 improved
          1.5% to 10.5%, respectively. "Best" mode speed is consistent with the
          Cayuga release.

      - Quality:
          Encoder quality in the single stream case is consistent with the Cayuga
          release.

      - Bug Fixes:
          This release fixes an OOB read decoder crash bug present in v0.9.7
          related to the clamping of motion vectors in SPLITMV blocks. This
          behavior could be triggered by corrupt input or by starting
          decoding from a P-frame.

    2011-08-15 v0.9.7-p1 "Cayuga" patch 1
      This is an incremental bugfix release against Cayuga. All users of that
      release are strongly encouraged to upgrade.

        - Fix potential OOB reads (cdae03a)

              An unbounded out of bounds read was discovered when the
              decoder was requested to perform error concealment (new in
              Cayuga) given a frame with corrupt partition sizes.

              A bounded out of bounds read was discovered affecting all
              versions of libvpx. Given an multipartition input frame that
              is truncated between the mode/mv partition and the first
              residiual paritition (in the block of partition offsets), up
              to 3 extra bytes could have been read from the source buffer.
              The code will not take any action regardless of the contents
              of these undefined bytes, as the truncated buffer is detected
              immediately following the read based on the calculated
              starting position of the coefficient partition.

        - Fix potential error concealment crash when the very first frame
          is missing or corrupt (a609be5)

        - Fix significant artifacts in error concealment (a4c2211, 99d870a)

        - Revert 1-pass CBR rate control changes (e961317)
          Further testing showed this change produced undesirable visual
          artifacts, rolling back for now.

    2011-08-02 v0.9.7 "Cayuga"
      Our third named release, focused on a faster, higher quality, encoder.

      - Upgrading:
        This release is backwards compatible with Aylesbury (v0.9.5) and
        Bali (v0.9.6). Users of older releases should refer to the Upgrading
        notes in this document for that release.

      - Enhancements:
              Stereo 3D format support for vpxenc
              Runtime detection of available processor cores.
              Allow specifying --end-usage by enum name
              vpxdec: test for frame corruption
              vpxenc: add quantizer histogram display
              vpxenc: add rate histogram display
              Set VPX_FRAME_IS_DROPPABLE
              update configure for ios sdk 4.3
              Avoid text relocations in ARM vp8 decoder
              Generate a vpx.pc file for pkg-config.
              New ways of passing encoded data between encoder and decoder.

      - Speed:
          This release includes across-the-board speed improvements to the
          encoder. On x86, these measure at approximately 11.5% in Best mode,
          21.5% in Good mode (speed 0), and 22.5% in Realtime mode (speed 6).
          On ARM Cortex A9 with Neon extensions, real-time encoding of video
          telephony content is 35% faster than Bali on single core and 48%
          faster on multi-core. On the NVidia Tegra2 platform, real time
          encoding is 40% faster than Bali.

          Decoder speed was not a priority for this release, but improved
          approximately 8.4% on x86.

              Reduce motion vector search on alt-ref frame.
              Encoder loopfilter running in its own thread
              Reworked loopfilter to precalculate more parameters
              SSE2/SSSE3 optimizations for build_predictors_mbuv{,_s}().
              Make hor UV predict ~2x faster (73 vs 132 cycles) using SSSE3.
              Removed redundant checks
              Reduced structure sizes
              utilize preload in ARMv6 MC/LPF/Copy routines
              ARM optimized quantization, dfct, variance, subtract
              Increase chrow row alignment to 16 bytes.
              disable trellis optimization for first pass
              Write SSSE3 sub-pixel filter function
              Improve SSE2 half-pixel filter funtions
              Add vp8_sub_pixel_variance16x8_ssse3 function
              Reduce unnecessary distortion computation
              Use diamond search to replace full search
              Preload reference area in sub-pixel motion search (real-time mode)

      - Quality:
          This release focused primarily on one-pass use cases, including
          video conferencing. Low latency data rate control was significantly
          improved, improving streamability over bandwidth constrained links.
          Added support for error concealment, allowing frames to maintain
          visual quality in the presence of substantial packet loss.

              Add rc_max_intra_bitrate_pct control
              Limit size of initial keyframe in one-pass.
              Improve framerate adaptation
              Improved 1-pass CBR rate control
              Improved KF insertion after fades to still.
              Improved key frame detection.
              Improved activity masking (lower PSNR impact for same SSIM boost)
              Improved interaction between GF and ARFs
              Adding error-concealment to the decoder.
              Adding support for independent partitions
              Adjusted rate-distortion constants

      - Bug Fixes:
              Removed firstpass motion map
              Fix parallel make install
              Fix multithreaded encoding for 1 MB wide frame
              Fixed iwalsh_neon build problems with RVDS4.1
              Fix semaphore emulation, spin-wait intrinsics on Windows
              Fix build with xcode4 and simplify GLOBAL.
              Mark ARM asm objects as allowing a non-executable stack.
              Fix vpxenc encoding incorrect webm file header on big endian

    2011-03-07 v0.9.6 "Bali"
      Our second named release, focused on a faster, higher quality, encoder.

      - Upgrading:
        This release is backwards compatible with Aylesbury (v0.9.5). Users
        of older releases should refer to the Upgrading notes in this
        document for that release.

      - Enhancements:
          vpxenc --psnr shows a summary when encode completes
          --tune=ssim option to enable activity masking
          improved postproc visualizations for development
          updated support for Apple iOS to SDK 4.2
          query decoder to determine which reference frames were updated
          implemented error tracking in the decoder
          fix pipe support on windows

      - Speed:
          Primary focus was on good quality mode, speed 0. Average improvement
          on x86 about 40%, up to 100% on user-generated content at that speed.
          Best quality mode speed improved 35%, and realtime speed 10-20%. This
          release also saw significant improvement in realtime encoding speed
          on ARM platforms.

            Improved encoder threading
            Dont pick encoder filter level when loopfilter is disabled.
            Avoid double copying of key frames into alt and golden buffer
            FDCT optimizations.
            x86 sse2 temporal filter
            SSSE3 version of fast quantizer
            vp8_rd_pick_best_mbsegmentation code restructure
            Adjusted breakout RD for SPLITMV
            Changed segmentation check order
            Improved rd_pick_intra4x4block
            Adds armv6 optimized variance calculation
            ARMv6 optimized sad16x16
            ARMv6 optimized half pixel variance calculations
            Full search SAD function optimization in SSE4.1
            Improve MV prediction accuracy to achieve performance gain
            Improve MV prediction in vp8_pick_inter_mode() for speed>3

      - Quality:
          Best quality mode improved PSNR 6.3%, and SSIM 6.1%. This release
          also includes support for "activity masking," which greatly improves
          SSIM at the expense of PSNR. For now, this feature is available with
          the --tune=ssim option. Further experimentation in this area
          is ongoing. This release also introduces a new rate control mode
          called "CQ," which changes the allocation of bits within a clip to
          the sections where they will have the most visual impact.

            Tuning for the more exact quantizer.
            Relax rate control for last few frames
            CQ Mode
            Limit key frame quantizer for forced key frames.
            KF/GF Pulsing
            Add simple version of activity masking.
            make rdmult adaptive for intra in quantizer RDO
            cap the best quantizer for 2nd order DC
            change the threshold of DC check for encode breakout

      - Bug Fixes:
          Fix crash on Sparc Solaris.
          Fix counter of fixed keyframe distance
          ARNR filter pointer update bug fix
          Fixed use of motion percentage in KF/GF group calc
          Changed condition for using RD in Intra Mode
          Fix encoder real-time only configuration.
          Fix ARM encoder crash with multiple token partitions
          Fixed bug first cluster timecode of webm file is wrong.
          Fixed various encoder bugs with odd-sized images
          vp8e_get_preview fixed when spatial resampling enabled
          quantizer: fix assertion in fast quantizer path
          Allocate source buffers to be multiples of 16
          Fix for manual Golden frame frequency
          Fix drastic undershoot in long form content

    2010-10-28 v0.9.5 "Aylesbury"
      Our first named release, focused on a faster decoder, and a better encoder.

      - Upgrading:
        This release incorporates backwards-incompatible changes to the
        ivfenc and ivfdec tools. These tools are now called vpxenc and vpxdec.

        vpxdec
          * the -q (quiet) option has been removed, and replaced with
            -v (verbose). the output is quiet by default. Use -v to see
            the version number of the binary.

          * The default behavior is now to write output to a single file
            instead of individual frames. The -y option has been removed.
            Y4M output is the default.

          * For raw I420/YV12 output instead of Y4M, the --i420 or --yv12
            options must be specified.

              $ ivfdec -o OUTPUT INPUT
              $ vpxdec --i420 -o OUTPUT INPUT

          * If an output file is not specified, the default is to write
            Y4M to stdout. This makes piping more natural.

              $ ivfdec -y -o - INPUT | ...
              $ vpxdec INPUT | ...

          * The output file has additional flexibility for formatting the
            filename. It supports escape characters for constructing a
            filename from the width, height, and sequence number. This
            replaces the -p option. To get the equivalent:

              $ ivfdec -p frame INPUT
              $ vpxdec --i420 -o frame-%wx%h-%4.i420 INPUT

        vpxenc
          * The output file must be specified with -o, rather than as the
            last argument.

              $ ivfenc <options> INPUT OUTPUT
              $ vpxenc <options> -o OUTPUT INPUT

          * The output defaults to webm. To get IVF output, use the --ivf
            option.

              $ ivfenc <options> INPUT OUTPUT.ivf
              $ vpxenc <options> -o OUTPUT.ivf --ivf INPUT

      - Enhancements:
          ivfenc and ivfdec have been renamed to vpxenc, vpxdec.
          vpxdec supports .webm input
          vpxdec writes .y4m by default
          vpxenc writes .webm output by default
          vpxenc --psnr now shows the average/overall PSNR at the end
          ARM platforms now support runtime cpu detection
          vpxdec visualizations added for motion vectors, block modes, references
          vpxdec now silent by default
          vpxdec --progress shows frame-by-frame timing information
          vpxenc supports the distinction between --fps and --timebase
          NASM is now a supported assembler
          configure: enable PIC for shared libs by default
          configure: add --enable-small
          configure: support for ppc32-linux-gcc
          configure: support for sparc-solaris-gcc

      - Bugs:
          Improve handling of invalid frames
          Fix valgrind errors in the NEON loop filters.
          Fix loopfilter delta zero transitions
          Fix valgrind errors in vp8_sixtap_predict8x4_armv6().
          Build fixes for darwin-icc

      - Speed:
          20-40% (average 28%) improvement in libvpx decoder speed,
          including:
            Rewrite vp8_short_walsh4x4_sse2()
            Optimizations on the loopfilters.
            Miscellaneous improvements for Atom
            Add 4-tap version of 2nd-pass ARMv6 MC filter.
            Improved multithread utilization
            Better instruction choices on x86
            reorder data to use wider instructions
            Update NEON wide idcts
            Make block access to frame buffer sequential
            Improved subset block search
            Bilinear subpixel optimizations for ssse3.
            Decrease memory footprint

          Encoder speed improvements (percentage gain not measured):
            Skip unnecessary search of identical frames
            Add SSE2 subtract functions
            Improve bounds checking in vp8_diamond_search_sadx4()
            Added vp8_fast_quantize_b_sse2

      - Quality:
          Over 7% overall PSNR improvement (6.3% SSIM) in "best" quality
          encoding mode, and up to 60% improvement on very noisy, still
          or slow moving source video

            Motion compensated temporal filter for Alt-Ref Noise Reduction
            Improved use of trellis quantization on 2nd order Y blocks
            Tune effect of motion on KF/GF boost in two pass
            Allow coefficient optimization for good quality speed 0.
            Improved control of active min quantizer for two pass.
            Enable ARFs for non-lagged compress

    2010-09-02 v0.9.2
      - Enhancements:
          Disable frame dropping by default
          Improved multithreaded performance
          Improved Force Key Frame Behaviour
          Increased rate control buffer level precision
          Fix bug in 1st pass motion compensation
          ivfenc: correct fixed kf interval, --disable-kf
      - Speed:
          Changed above and left context data layout
          Rework idct calling structure.
          Removed unnecessary MB_MODE_INFO copies
          x86: SSSE3 sixtap prediction
          Reworked IDCT to include reconstruction (add) step
          Swap alt/gold/new/last frame buffer ptrs instead of copying.
          Improve SSE2 loopfilter functions
          Change bitreader to use a larger window.
          Avoid loopfilter reinitialization when possible
      - Quality:
          Normalize quantizer's zero bin and rounding factors
          Add trellis quantization.
          Make the quantizer exact.
          Updates to ARNR filtering algorithm
          Fix breakout thresh computation for golden & AltRef frames
          Redo the forward 4x4 dct
          Improve the accuracy of forward walsh-hadamard transform
          Further adjustment of RD behaviour with Q and Zbin.
      - Build System:
          Allow linking of libs built with MinGW to MSVC
          Fix target auto-detection on mingw32
          Allow --cpu= to work for x86.
          configure: pass original arguments through to make dist
          Fix builds without runtime CPU detection
          msvs: fix install of codec sources
          msvs: Change devenv.com command line for better msys support
          msvs: Add vs9 targets.
          Add x86_64-linux-icc target
      - Bugs:
          Potential crashes on older MinGW builds
          Fix two-pass framrate for Y4M input.
          Fixed simple loop filter, other crashes on ARM v6
          arm: fix missing dependency with --enable-shared
          configure: support directories containing .o
          Replace pinsrw (SSE) with MMX instructions
          apple: include proper mach primatives
          Fixed rate control bug with long key frame interval.
          Fix DSO link errors on x86-64 when not using a version script
          Fixed buffer selection for UV in AltRef filtering

    2010-06-17 v0.9.1
      - Enhancements:
          * ivfenc/ivfdec now support YUV4MPEG2 input and pipe I/O
          * Speed optimizations
      - Bugfixes:
          * Rate control
          * Prevent out-of-bounds accesses on invalid data
      - Build system updates:
          * Detect toolchain to be used automatically for native builds
          * Support building shared libraries
          * Better autotools emulation (--prefix, --libdir, DESTDIR)
      - Updated LICENSE
          * http://webmproject.blogspot.com/2010/06/changes-to-webm-open-source-license.html

    2010-05-18 v0.9.0
      - Initial open source release. Welcome to WebM and VP8!