1. 30 Jul, 2012 1 commit
    • Deb Mukherjee's avatar
      Adds support for switchable interpolation filters. · 52597441
      Deb Mukherjee authored
      Allows for swtiching/setting interpolation filters at the MB
      level. A frame level flag indicates whether to use a specifc
      filter for the entire frame or to signal the interpolation
      filter for each MB. When switchable filters are used, the
      encoder chooses between 8-tap and 8-tap sharp filters. The
      code currently has options to explore other variations as well,
      which will be cleaned up subsequently.
      
      One issue with the framework is that encoding is slow. I
      tried to do some tricks to speed things up but it is still slow.
      Decoding speed should not be affected since the number of
      filter taps remain unchanged.
      
      With the current version, we are up 0.5% on derf on average but
      some videos city/mobile improve by close to 4 and 2% respectively.
      If we did a full-search by turning the SEARCH_BEST_FILTER flag
      on, the results are somewhat better.
      
      The framework can be combined with filtered prediction, and I
      seek feedback regarding that.
      
      Rebased.
      
      Change-Id: I8f632cb2c111e76284140a2bd480945d6d42b77a
      52597441
  2. 27 Jul, 2012 1 commit
    • Deb Mukherjee's avatar
      Merges several experiments · 9984a155
      Deb Mukherjee authored
      The following five experiments are merged:
      
      newentropy
      newupdate
      adaptive_entropy (also includes a couple of parameter changes
                        that improves results a little
                        in common/entropymode.c and encoder/modecosts.c
                        that were not merged from the internal branch)
      newintramodes
      expanded_coef_context
      
      Change-Id: I8a142a831786ee9dc936f22be1d42a8bced7d270
      9984a155
  3. 17 Jul, 2012 1 commit
  4. 27 Jun, 2012 1 commit
    • Adrian Grange's avatar
      Added Prediction Filter to Mode Selection · bbc926dc
      Adrian Grange authored
      Added the ability to optionally filter the prediction data
      when inter modes are selected (excludes SPLITMV, for now).
      
      The mode selection loop considers both the filtered and
      non-filtered prediction data when choosing mode. The filter
      can be turned on/off at the frame-level, or signaled for
      each MB.
      
      Change-Id: I1b783c71d95a361ab36c761b07e8a6b06bc36822
      bbc926dc
  5. 26 Jun, 2012 1 commit
    • Deb Mukherjee's avatar
      Continued adaptive entropy coding · f3dff402
      Deb Mukherjee authored
      Incorporates mv_ref, mbsplit and second_mv into the adaptive
      entropy framework. The mv_ref framework has been modified from
      before.
      
      Adds some clean-ups and fixes.
      
      Results with the adaptive entropy experiment are currently up by
      +1.93% on derf; +2.33% std-hd and +1.87% yt-hd.
      
      Fixed a nasty intermittent bug.
      
      Change-Id: I4b1ac9f9483b48432597595195bfec05f31d1e39
      f3dff402
  6. 15 Jun, 2012 1 commit
    • Deb Mukherjee's avatar
      Adaptive entropy coding of coefficients, modes, mv. · 1fe85a35
      Deb Mukherjee authored
      This patch incorporates adaptive entropy coding of coefficient tokens,
      and mode/mv information based on distributions encountered in a frame.
      Specifically, there is an initial forward update to the probabilities
      in the bitstream as before for coding the symbols in the frame, however
      at the end of decoding each frame, the forward update to the
      probabilities is reverted and instead the probabilities are updated
      towards the actual distributions encountered within the frame.
      The amount of update is weighted by the number of hits within each
      context.
      
      Results on derf/hd/std-hd are all up by 1.6%.
      
      On derf, the most of the gains come from coefficients, however for the
      hd and std-hd sets, the most of the gains come from the mode/mv
      information updates.
      
      Change-Id: I708c0e11fdacafee04940fe7ae159ba6844005fd
      1fe85a35
  7. 08 May, 2012 1 commit
    • Yaowu Xu's avatar
      a number of fixes to entropy stats collection · 54cf1d9a
      Yaowu Xu authored
      1. block types
      There are only three types of blocks for 8x8 transformed MBs, i.e. Y
      block with DC does not exist for 8x8 transformed MBs as all MB using
      8x8 transform have 2nd order haar transform. This commit introduced
      a new macro BLOCK_TYPES_8X8 to reflect such fact.
      
      2. context counters
      This commit also fixed the mixed of context_counters between 4x4 and
      8x8 transformed MBs. The mixed use of the counters leads me to think
      the existing the context probabilities were not properly generated
      from 8x8 transformed MBs.
      
      3. redundant collecting in recoding
      The commit also corrected the code that accumulates entropy stats by
      making sure stats only collected for final packing, not during the
      recode loop
      
      Change-Id: I029f09f8f60bd0c3240cc392ff5c6d05435e322c
      54cf1d9a
  8. 25 Apr, 2012 2 commits
    • Yaowu Xu's avatar
      Merge QIMODE experiment · a16608ab
      Yaowu Xu authored
      This commit merge the QI mode experiment. As the experiment affects
      the encoding of intra coding modes on key frame only, the overall
      effect of the experiment on encoding tests is insignificant.
      
      Change-Id: I9e4e3933adface88867ad429cee3986e529c511d
      a16608ab
    • Yaowu Xu's avatar
      Merge UVINTRA experiment · c1814d26
      Yaowu Xu authored
      The commit merges the UVINTRA experiment and removed the related
      macros. The overall effect of the experiment is a small gain (.1%
      on derf)
      
      Change-Id: Ia34b3312fb9b5b34c9ba111bf0fa78c6f78ac80b
      c1814d26
  9. 11 Apr, 2012 1 commit
    • Paul Wilkins's avatar
      Refactoring of encode loop and bitstream packing · 13c6d1a8
      Paul Wilkins authored
      Some code re-factored / moved to allow the main
      pack operation inside the recode loop so  that the
      size estimate is accurate.
      
      Deletion of some redundant code relating to one pass.
      
      Aproximate improvement over March 27 code base:
      Derf 0.0%, YT 0.5%, YThd 0.3% Std_hd 0.25%
      
      Change-Id: Id2d071794ab44f0b52935f6fcdb5733d09a6bb86
      13c6d1a8
  10. 21 Mar, 2012 2 commits
  11. 15 Mar, 2012 1 commit
    • Yaowu Xu's avatar
      WebM Experimental Codec Branch Snapshot · 6035da54
      Yaowu Xu authored
      This is a code snapshot of experimental work currently ongoing for a
      next-generation codec.
      
      The codebase has been cut down considerably from the libvpx baseline.
      For example, we are currently only supporting VBR 2-pass rate control
      and have removed most of the code relating to coding speed, threading,
      error resilience, partitions and various other features.  This is in
      part to make the codebase easier to work on and experiment with, but
      also because we want to have an open discussion about how the bitstream
      will be structured and partitioned and not have that conversation
      constrained by past work.
      
      Our basic working pattern has been to initially encapsulate experiments
      using configure options linked to #IF CONFIG_XXX statements in the
      code. Once experiments have matured and we are reasonably happy that
      they give benefit and can be merged without breaking other experiments,
      we remove the conditional compile statements and merge them in.
      
      Current changes include:
      * Temporal coding experiment for segments (though still only 4 max, it
        will likely be increased).
      * Segment feature experiment - to allow various bits of information to
        be coded at the segment level. Features tested so far include mode
        and reference frame information, limiting end of block offset and
        transform size, alongside Q and loop filter parameters, but this set
        is very fluid.
      * Support for 8x8 transform - 8x8 dct with 2nd order 2x2 haar is used
        in MBs using 16x16 prediction modes within inter frames.
      * Compound prediction (combination of signals from existing predictors
        to create a new predictor).
      * 8 tap interpolation filters and 1/8th pel motion vectors.
      * Loop filter modifications.
      * Various entropy modifications and changes to how entropy contexts and
        updates are handled.
      * Extended quantizer range matched to transform precision improvements.
      
      There are also ongoing further experiments that we hope to merge in the
      near future: For example, coding of motion and other aspects of the
      prediction signal to better support larger image formats, use of larger
      block sizes (e.g. 32x32 and up) and lossless non-transform based coding
      options (especially for key frames). It is our hope that we will be
      able to make regular updates and we will warmly welcome community
      contributions.
      
      Please be warned that, at this stage, the codebase is currently slower
      than VP8 stable branch as most new code has not been optimized, and
      even the 'C' has been deliberately written to be simple and obvious,
      not fast.
      
      The following graphs have the initial test results, numbers in the
      tables measure the compression improvement in terms of percentage. The
      build has  the following optional experiments configured:
      --enable-experimental --enable-enhanced_interp --enable-uvintra
      --enable-high_precision_mv --enable-sixteenth_subpel_uv
      
      CIF Size clips:
      http://getwebm.org/tmp/cif/
      HD size clips:
      http://getwebm.org/tmp/hd/
      (stable_20120309 represents encoding results of WebM master branch
      build as of commit#7a159071)
      
      They were encoded using the following encode parameters:
      --good --cpu-used=0 -t 0 --lag-in-frames=25 --min-q=0 --max-q=63
      --end-usage=0 --auto-alt-ref=1 -p 2 --pass=2 --kf-max-dist=9999
      --kf-min-dist=0 --drop-frame=0 --static-thresh=0 --bias-pct=50
      --minsection-pct=0 --maxsection-pct=800 --sharpness=0
      --arnr-maxframes=7 --arnr-strength=3(for HD,6 for CIF)
      --arnr-type=3
      
      Change-Id: I5c62ed09cfff5815a2bb34e7820d6a810c23183c
      6035da54
  12. 01 Mar, 2012 1 commit
  13. 29 Feb, 2012 1 commit
  14. 28 Feb, 2012 3 commits
    • Deb Mukherjee's avatar
      Initial refactoring of high_precision mv code. · 3e1cad9c
      Deb Mukherjee authored
      This is the first patch for refactoring of the code related to
      high-precision mv, so that 1/4 and 1/8 pel motion vectors can
      co-exist in the same bit-stream by use of a frame level flag.
      The current patch works fine for only use of 1/4th and
      only use of 1/8th pel mv, but there are some issues with the
      mode switching in between. Subsequent patches on this change Id
      will fix the remaining issues.
      
      Patch 2: Adds fixes to make sure that multiple mv precisions can
      co-exist in the bit-stream. Frame level switching has been tested
      to work correctly.
      
      Patch 3: Fixes lines exceeding 80 char
      
      Patch 4:
      http://www.corp.google.com/~debargha/vp8_results/enhinterp.html
      
      Results on derf after ssse3 bugfix, compared to everything
      enabled but the 8-tap, 1/8-subpel and 1/16-subpel uv. Overall the
      gains are about 3% now. Hopefully there are no more bugs lingering.
      Apparently the sse3 bug affected the quartel subpel results more than
      the eighth pel ones (which is understandabale because one bad predictor
      due to the bug, matters less if there are a lot more subpel options
      available as in the 1/8 subpel case).
      The results in the 4th column correspond to the current settings.
      The first two columns correspond to two settings of adaptive switching
      of the 1/4 or 1/8 subpel mode based on initial Q estimate. These
      do not work as good as just using 1/8 all the time yet.
      
      Change-Id: I3ef392ad338329f4d68a85257a49f2b14f3af472
      3e1cad9c
    • Paul Wilkins's avatar
      Experimental branch code clean up. · 25c127f5
      Paul Wilkins authored
      Removal of some further code relating to partitions
      and error resilience.
      
      Spelling correction.
      
      Change-Id: I36067aae67a4a23bec359541dda3400b0bbf26d0
      25c127f5
    • Paul Wilkins's avatar
      Code Simplification · b6f02c85
      Paul Wilkins authored
      Removal of code relating to token partitioning
      
      Change-Id: Iaf3c88d6758639a55bd92c3be5c51e6bed407a3c
      b6f02c85
  15. 10 Feb, 2012 3 commits
    • Paul Wilkins's avatar
      Removal of threading code. · 2615ca5d
      Paul Wilkins authored
      For the experimental branch we are trying to slim the codebase
      down removing features such as threading for now which complicate
      the process of development and testing.
      
      Change-Id: I657c0246aef4d1fa8c8ffc6a1adfeee45bce8e24
      2615ca5d
    • Ronald S. Bultje's avatar
      Improved coding using 8x8 transform · f64725a0
      Ronald S. Bultje authored
      In summary, this commit encompasses a series of changes in attempt to
      improve the 8x8 transform based coding to help overall compression
      quality, please refer to the detailed commit history below for what
      are the rationale underly the series of changes:
      
      a. A frame level flag to indicate if 8x8 transform is used at all.
      b. 8x8 transform is not used for key frames and small image size.
      c. On inter coded frame, macroblocks using modes B_PRED, SPLIT_MV
      and I8X8_PRED are forced to using 4x4 transform based coding, the
      rest uses 8x8 transform based coding.
      d. Encoder and decoder has the same assumption on the relationship
      between prediction modes and transform size, therefore no signaling
      is encoded in bitstream.
      e. Mode decision process now calculate the rate and distortion scores
      using their respective transforms.
      
      Overall test results:
      1. HD set
      http://www.corp.google.com/~yaowu/no_crawl/t8x8/HD_t8x8_20120206.html
      (avg psnr: 3.09% glb psnr: 3.22%, ssim: 3.90%)
      2. Cif set:
      http://www.corp.google.com/~yaowu/no_crawl/t8x8/cif_t8x8_20120206.html
      (avg psnr: -0.03%, glb psnr: -0.02%, ssim: -0.04%)
      It should be noted here, as 8x8 transform coding itself is disabled
      for cif size clips, the 0.03% loss is purely from the 1 bit/frame
      flag overhead on if 8x8 transform is used or not for the frame.
      
      ---patch history for future reference---
      Patch 1:
      this commit tries to select transform size based on macroblock
      prediction mode. If the size of a prediction mode is 16x16, then
      the macroblock is forced to use 8x8 transform. If the prediction
      mode is B_PRED, SPLITMV or I8X8_PRED, then the macroblock is forced
      to use 4x4 transform. Tests on the following HD clips showed mixed
      results: (all hd clips only used first 100 frames in the test)
      
      http://www.corp.google.com/~yaowu/no_crawl/t8x8/hdmodebased8x8.html
      http://www.corp.google.com/~yaowu/no_crawl/t8x8/hdmodebased8x8_log.html
      
      while the results are mixed and overall negative, it is interesting to
      see 8x8 helped a few of the clips.
      
      Patch 2:
      this patch tries to hard-wire selection of transform size based on
      prediction modes without using segmentation to signal the transform size.
      encoder and decoder both takes the same assumption that all macroblocks
      use 8x8 transform except when prediciton mode is B_PRED, I8X8_PRED or
      SPLITMV. Test results are as follows:
      
      http://www.corp.google.com/~yaowu/no_crawl/t8x8/cifmodebase8x8_0125.html
      http://www.corp.google.com/~yaowu/no_crawl/t8x8/hdmodebased8x8_0125log.html
      
      Interestingly, by removing the overhead or coding the segmentation, the
      results on this limited HD set have turn positive on average.
      
      Patch 3:
      this patch disabled the usage of 8x8 transform on key frames, and kept the
      logic from patch 2 for inter frames only. test results on HD set turned
      decidedly positive with 8x8 transform enabled on inter frame with 16x16
      prediction modes: (avg psnr: .81% glb psnr: .82 ssim: .55%)
      
      http://www.corp.google.com/~yaowu/no_crawl/t8x8/hdintermode8x8_0125.html
      results on cif set still negative overall
      
      Patch 4:
      continued from last patch, but now in mode decision process, the rate and
      distortion estimates are computed based on 8x8 transform results for MBs
      with modes associated with 8x8 transform. This patch also fixed a problem
      related to segment based eob coding when 8x8 transform is used. The patch
      significantly improved the results on HD clips:
      
      http://www.corp.google.com/~yaowu/no_crawl/t8x8/hd8x8RDintermode.html
      (avg psnr: 2.70% glb psnr: 2.76% ssim: 3.34%)
      results on cif also improved, though they are still negative compared to
      baseline that uses 4x4 transform only:
      http://www.corp.google.com/~yaowu/no_crawl/t8x8/cif8x8RDintermode.html
      (avg psnr: -.78% glb psnr: -.86% ssim: -.19%)
      
      Patch 5:
      This patch does 3 things:
      a. a bunch of decoder bug fixes, encodings and decodings were verified
      to have matched recon buffer on a number of encodes on cif size mobile and
      hd version of _pedestrian.
      b. the patch further improved the rate distortion calculation of MBS that
      use 8x8 transform. This provided some further gain on compression.
      c. the patch also got the experimental work SEG_LVL_EOB to work with 8x8
      transformed macroblock, test results indicates it improves the cif set
      but hurt the HD set slightly.
      
      Tests results on HD clips:
      http://www.corp.google.com/~yaowu/no_crawl/t8x8/HD_t8x8_20120201.html
      (avg psnr: 3.19% glb psnr: 3.30% ssim: 3.93%)
      
      Test results on cif clips:
      http://www.corp.google.com/~yaowu/no_crawl/t8x8/cif_t8x8_20120201.html
      (avg psnr: -.47% glb psnr: -.51% ssim: +.28%)
      
      Patch 6:
      Added a frame level flag to indicate if 8x8 transform is allowed at all.
      temporarily the decision is based on frame size, can be optimized later
      one. This get the cif results to basically unchanged, with one bit per
      frame overhead on both cif and hd clips.
      
      Patch 8:
      Rebase and Merge to head by PGW.
      Fixed some suspect 4s that look like hey should be 64s in regard
      to segmented EOB. Perhaps #defines would be bette.
      Bulit and tested without T8x8 enabled and produces unchanged
      output.
      
      Patch 9:
      Corrected misalligned code/decode of "txfm_mode" bit.
      Limited testing for correct encode and decode with
      T8x8 configured on derf clips.
      
      Change-Id: I156e1405d25f81579d579dff8ab9af53944ec49c
      f64725a0
    • Ronald S. Bultje's avatar
      Merge dualpred (compound prediction) experiment. · 29e4d7e8
      Ronald S. Bultje authored
      Change-Id: Ieaaa07c50eae41118596197f6a4d848135946e41
      29e4d7e8
  16. 09 Feb, 2012 3 commits
    • Paul Wilkins's avatar
      Merge Extended Q experiment. · 3e9890a3
      Paul Wilkins authored
      Merge the extended Q experiment as indicated by the
      
      Change-Id: I02d9e654fff9998cc7e9e2f1f5cd838dad8fb431
      3e9890a3
    • Paul Wilkins's avatar
      Merge COMPRED · cf8af867
      Paul Wilkins authored
      Merged in most of the current common prediction changes
      that were under the #if CONFIG_COMPRED option.
      
      Change-Id: If4e6f61dbe7b86dd449f6effbe93b5eb7e893885
      cf8af867
    • Paul Wilkins's avatar
      Dual pred flag · 8266abfe
      Paul Wilkins authored
      Further changes to make experiments with the context
      used for coding the dual pred flag easier.
      
      Current best performing method tested on derf is a two
      element context based on reference frame. I also tried
      various combinations of mode and reference frame as
      shown in commented out case using up to 6 contexts.
      
      Derf +0.26 overall psnr +0.15% ssim vs original method.
      
      Change-Id: I64c21ddec0abbb27feaaeaa1da2e9f164ebaca03
      8266abfe
  17. 06 Feb, 2012 3 commits
    • Paul Wilkins's avatar
      Merged NEWNEAR experiment · 9c9300f5
      Paul Wilkins authored
      This commit merges the NEWNEAR experiment such that it
      is effectively always on.
      
      The fact that there were changes in the threading code again
      highlights the need to strip out such features during the
      bitstream development phase as trying to maintain this code
      (especially as it is not being tested) slows the development cycle.
      
      Change-Id: I8b34950a1333231ced9928aa11cd6d6459984b65
      9c9300f5
    • Paul Wilkins's avatar
      Moved prob_dualpred to common. · c98e9d28
      Paul Wilkins authored
      Moved the prob_dualpred[] sturcture to common.
      Created common prediction entry for Dual flag.
      
      Change-Id: I9ac3d128bae6114f09e5c18216d4b95cf36453d5
      c98e9d28
    • Paul Wilkins's avatar
      Modified prediction behavior for reference frame. · 58ec6fe8
      Paul Wilkins authored
      Trial of a modified prediction function that ranks each possible
      reference frame based on a combination of local usage and
      frame level probability. The code is a bit cleaner and simpler.
      
      In direct comparison with old unpredicted method with segment level
      coding turned off for mode,ref & EOB the prediction gives a gain on derf
      of around 0.4%. There is some further gain from bug fixes over earlier code.
      
      With segment coding on the prediction method is slightly -ve on some very
      easy clips (at low rates) due to slightly higher overheads, but better on harder
      clips. Overall neutral on derf in direct comparison on latest code base, but
      compared to earlier code without bug fixes about +0.7% overall psnr
      +0.3% SSIM.
      
      Change-Id: I5b8474658b208134d352d24f6517f25795490789
      58ec6fe8
  18. 31 Jan, 2012 3 commits
    • Paul Wilkins's avatar
      Added common prediction modules. · b2f64dff
      Paul Wilkins authored
      This function adds the common prediction modules,  some data structures
      and a config option but does not use them.
      
      It also corrects a bug in clearing down  the MODE_INFO border and introduces
      a new element that indicates if an entry corresponds to an "in image" macro block
      or is part of the border.
      
      Change-Id: Ib69eec0876173ebe9d1de9df9537d0b2447702e0
      b2f64dff
    • Paul Wilkins's avatar
      Moved some reference frame data structures into common. · 5f0f260f
      Paul Wilkins authored
      In this commit only the decoder side was updated.
      
      Change-Id: Ia9bd58da07d1a943f028e330f0489344e62b0d02
      5f0f260f
    • Paul Wilkins's avatar
      Moved some segmentation data structures. · fe96afa7
      Paul Wilkins authored
      Moved some segmentation data structures into VP8_COMMON
      
      Change-Id: I59c6e2edf7a0176e35319936eea450027aeb3b39
      fe96afa7
  19. 19 Dec, 2011 2 commits
    • Paul Wilkins's avatar
      Extend to 256 Q steps. · df4e79f7
      Paul Wilkins authored
      This commit extends the number of Q steps to 256 from 128.
      The q_trans[] array has been altered to distribute available Q index values
      (using the current 64 steps available as input parameters) evenly across the
      available range. This is coupled with the fact that each Q step where possible
      now equates to a fixed % change in the quantizer. This may want refinement
      later especially in terms of the granularity at the high quality end but is a
      reasonable starting point.
      
      Change-Id: I2aaa6874fa10ce05c958dd182947ce39f6f1eecb
      df4e79f7
    • Paul Wilkins's avatar
      Further QIndex realted Fixes: · fb807776
      Paul Wilkins authored
      Added code to support 256 index steps instead of 128 but disabled for now.
      Replace hard wired table vp8cx_base_skip_false_prob[128]
      Observed Qindex problem with setting minimum loop filter value.
      (Experiment code using real Q in place but for now just returning 0. This has a big
      beneficial effect on some clips, particularly waterfall which shows 5% ssim gain)
      
      Change-Id: I2f7117de8adc1797164c106aa13effc900a1467e
      fb807776
  20. 09 Dec, 2011 2 commits
  21. 07 Dec, 2011 3 commits
    • Yaowu Xu's avatar
      Removed #if CONFIG_MULCONTEXT · b70f23ca
      Yaowu Xu authored
      This commit removed the macro CONFIG_MULCONTEXT, which was used to
      indicate the experiment code for using separate context for altref
      and normal frames. This commit made the change fully merged in.
      
      Change-Id: I525f927f68e2365d37b340ef23b836a136a4f70b
      b70f23ca
    • Yaowu Xu's avatar
      Removed #if CONFIG_I8X8 · d37cd976
      Yaowu Xu authored
      This commit removed the macro CONFIG_I8X8, which was used to indicate
      the 8x8 intra prediction experiment, made the change fully merged in.
      
      Change-Id: Iafa4443781ce6e83f5591c12ba615a0e92ce0ea0
      d37cd976
    • Yaowu Xu's avatar
      made vp8_mode_context adaptive · 76feb965
      Yaowu Xu authored
      vp8_mode_contexts[] is an entropy table used to code inter mode
      choices. It was a fixed constant table. This commit made the entropy
      context adaptive. Tests on derf set showed very good consistent gains
      on all metrics: avg psnr .47%, overall psnr .46% and ssim .40%.
      
      http://www.corp.google.com/~yaowu/no_crawl/newModeContext.html
      
      Change-Id: Ia62b14485c948e2b74586118619c5eb2068b43b2
      76feb965
  22. 06 Dec, 2011 1 commit
    • Ronald S. Bultje's avatar
      Dual 16x16 inter prediction. · 60cb39da
      Ronald S. Bultje authored
      This patch introduces the concept of dual inter16x16 prediction. A
      16x16 inter-predicted macroblock can use 2 references instead of 1,
      where both references use the same mvmode (new, near/est, zero). In the
      case of newmv, this means that two MVs are coded instead of one. The
      frame can be encoded in 3 ways: all MBs single-prediction, all MBs dual
      prediction, or per-MB single/dual prediction selection ("hybrid"), in
      which case a single bit is coded per-MB to indicate whether the MB uses
      single or dual inter prediction.
      
      In the future, we can (maybe?) get further gains by mixing this with
      Adrian's 32x32 work, per-segment dual prediction settings, or adding
      support for dual splitmv/8x8mv inter prediction.
      
      Gain (on derf-set, CQ mode) is ~2.8% (SSIM) or ~3.6% (glb PSNR). Most
      gain is at medium/high bitrates, but there's minor gains at low bitrates
      also. Output was confirmed to match between encoder and decoder.
      
      Note for optimization people: this patch introduces a 2nd version of
      16x16/8x8 sixtap/bilin functions, which does an avg instead of a
      store. They may want to look and make sure this is implemented to
      their satisfaction so we can optimize it best in the future.
      
      Change-ID: I59dc84b07cbb3ccf073ac0f756d03d294cb19281
      60cb39da
  23. 02 Dec, 2011 1 commit
    • Yaowu Xu's avatar
      added separate entropy context for alt_ref · acf5d20c
      Yaowu Xu authored
      This commit added code to keep track of separate entropy contexts for
      normal frames and alt ref frames. The underly assumption was that the
      two type of frames have different entropy characteristics given they
      typically have quite different quantization levels. By keeping entropy
      contexts separate, it helps the entropy context distribution to be more
      closely adapted to each frame type.
      
      Tests on derf set showed a good and very consistent gain on all clips
      on all metrics, avg psnr: 0.89%, overall psnr: 0.84% and ssim 0.93%.
      
      http://www.corp.google.com/~yaowu/no_crawl/mulcontext.html
      
      Change-Id: I15bc9697f6ff7829042911fe0c62930585d7e65d
      acf5d20c
  24. 04 Nov, 2011 1 commit
    • Yaowu Xu's avatar
      make uv intra mode coding adaptive to Y mode · 2bbde250
      Yaowu Xu authored
      This commit tries to do UV intra mode coding adaptive to Y intra mode.
      Entropy context is defined as conditional PDF of uv intra mode given
      the Y mode. All constants are normalized with 256 to be fit in 8 bits.
      
      This provides further coding efficiency beyond the quantizer adaptive
      y intra mode coding. Consistent gains were observed on all clips and
      all bit rates for HD all key encoding tests.
      
      To test, configure with
      --enable-experimental --enable-uvintra
      
      Change-Id: I2d78d73f143127f063e19bd0bac3b68c418d756a
      2bbde250