1. 18 Oct, 2016 1 commit
  2. 17 Jan, 2016 1 commit
  3. 14 Jan, 2016 1 commit
  4. 13 Jan, 2016 3 commits
    • Claudio Freire's avatar
      AAC encoder: encode out-of-phase I/S efficiently · 699c2ee5
      Claudio Freire authored
      Use the ability to invert phase with ms_mask instead of changing
      the codebook when possible, to avoid having to switch codebooks
      if some bands are INTENSTY_BT and others are INTENSITY_BT2, since
      usually a set ms_mask uses less bits that a codebook change. While
      it may not always be a win (ie: if it causes an ms_mask bitmap
      to be sent when it wouldn't have been otherwise), it's unlikely
      since the ms_mask bitmap will almost always be there already for
      M/S itself.
      699c2ee5
    • Claudio Freire's avatar
      AAC encoder: fix I/S relative error evaluation · aa64a483
      Claudio Freire authored
      The relative error between two encoding strategies is the simple
      difference of rate-distortion values, and not the absolute
      difference. An absolute measure would allow worsening of the
      quantization error as well as improving.
      aa64a483
    • Claudio Freire's avatar
      AAC encoder: in IS, fix index of sf_idx, band_type · 4dcb69cc
      Claudio Freire authored
      Correct addressing of sf_idx and band_type arrays in I/S code.
      
      Both arrays don't guarantee valid values for subwindows at all
      times, depending on which coder is being used, which could result
      in reading of garbage values. Instead, only the first subwindow
      in the window group has to be used, ie: use w*16+g instead of
      (w+w2)*16+g
      4dcb69cc
  5. 21 Dec, 2015 1 commit
  6. 02 Dec, 2015 1 commit
    • Claudio Freire's avatar
      AAC encoder: improve SF range utilization · ca203e99
      Claudio Freire authored
      This patch does 4 things, all of which interact and thus it
      woudln't be possible to commit them separately without causing
      either quality regressions or assertion failures.
      
      Fate comparison targets don't all reflect improvements in
      quality, yet listening tests show substantially improved quality
      and stability.
      
      1. Increase SF range utilization.
      
      The spec requires SF delta values to be constrained within the
      range -60..60. The previous code was applying that range to
      the whole SF array and not only the deltas of consecutive values,
      because doing so requires smarter code: zeroing or otherwise
      skipping a band may invalidate lots of SF choices.
      
      This patch implements that logic to allow the coders to utilize
      the full dynamic range of scalefactors, increasing quality quite
      considerably, and fixing delta-SF-related assertion failures,
      since now the limitation is enforced rather than asserted.
      
      2. PNS tweaks
      
      The previous modification makes big improvements in twoloop's
      efficiency, and every time that happens PNS logic needs to be
      tweaked accordingly to avoid it from stepping all over twoloop's
      decisions. This patch includes modifications of the sort.
      
      3. Account for lowpass cutoff during PSY analysis
      
      The closer PSY's allocation is to final allocation the better
      the quality is, and given these modifications, twoloop is now
      very efficient at avoiding holes. Thus, to compute accurate
      thresholds, PSY needs to account for the lowpass applied
      implicitly during twoloop (by zeroing high bands).
      
      This patch makes twoloop set the cutoff in psymodel's context
      the first time it runs, and makes PSY account for it during
      threshold computation, making PE and threshold computations
      closer to the final allocation and thus achieving better
      subjective quality.
      
      4. Tweaks to RC lambda tracking loop in relation to PNS
      
      Without this tweak some corner cases cause quality regressions.
      Basically, lambda needs to react faster to overall bitrate
      efficiency changes since now PNS can be quite successful in
      enforcing maximum bitrates, when PSY allocates too many bits
      to the lower bands, suppressing the signals RC logic uses to
      lower lambda in those cases and causing aggressive PNS.
      
      This tweak makes PNS much less aggressive, though it can still
      use some further tweaks.
      
      Also update MIPS specializations and adjust fuzz
      
      Also in lavc/mips/aacpsy_mips.h: remove trailing whitespace
      ca203e99
  7. 11 Oct, 2015 1 commit
    • Claudio Freire's avatar
      AAC encoder: Extensive improvements · 01ecb717
      Claudio Freire authored
      This finalizes merging of the work in the patches in ticket #2686.
      
      Improvements to twoloop and RC logic are extensive.
      
      The non-exhaustive list of twoloop improvments includes:
       - Tweaks to distortion limits on the RD optimization phase of twoloop
       - Deeper search in twoloop
       - PNS information marking to let twoloop decide when to use it
         (turned out having the decision made separately wasn't working)
       - Tonal band detection and priorization
       - Better band energy conservation rules
       - Strict hole avoidance
      
      For rate control:
       - Use psymodel's bit allocation to allow proper use of the bit
         reservoir. Don't work against the bit reservoir by moving lambda
         in the opposite direction when psymodel decides to allocate more/less
         bits to a frame.
       - Retry the encode if the effective rate lies outside a reasonable
         margin of psymodel's allocation or the selected ABR.
       - Log average lambda at the end. Useful info for everyone, but especially
         for tuning of the various encoder constants that relate to lambda
         feedback.
      
      Psy:
       - Do not apply lowpass with a FIR filter, instead just let the coder
         zero bands above the cutoff. The FIR filter induces group delay,
         and while zeroing bands causes ripple, it's lost in the quantization
         noise.
       - Experimental VBR bit allocation code
       - Tweak automatic lowpass filter threshold to maximize audio bandwidth
         at all bitrates while still providing acceptable, stable quality.
      
      I/S:
       - Phase decision fixes. Unrelated to #2686, but the bugs only surfaced
         when the merge was finalized. Measure I/S band energy accounting for
         phase, and prevent I/S and M/S from being applied both.
      
      PNS:
       - Avoid marking short bands with PNS when they're part of a window
         group in which there's a large variation of energy from one window
         to the next. PNS can't preserve those and the effect is extremely
         noticeable.
      
      M/S:
       - Implement BMLD protection similar to the specified in
         ISO-IEC/13818:7-2003, Appendix C Section 6.1. Since M/S decision
         doesn't conform to section 6.1, a different method had to be
         implemented, but should provide equivalent protection.
       - Move the decision logic closer to the method specified in
         ISO-IEC/13818:7-2003, Appendix C Section 6.1. Specifically,
         make sure M/S needs less bits than dual stereo.
       - Don't apply M/S in bands that are using I/S
      
      Now, this of course needed adjustments in the compare targets and
      fuzz factors of the AAC encoder's fate tests, but if wondering why
      the targets go up (more distortion), consider the previous coder
      was using too many bits on LF content (far more than required by
      psy), and thus those signals will now be more distorted, not less.
      
      The extra distortion isn't audible though, I carried extensive
      ABX testing to make sure.
      
      A very similar patch was also extensively tested by Kamendo2 in
      the context of #2686.
      01ecb717
  8. 06 Sep, 2015 2 commits
  9. 05 Sep, 2015 1 commit
    • Rostislav Pehlivanov's avatar
      aacenc_is: add a flag to use pure coefficients instead · 4565611b
      Rostislav Pehlivanov authored
      This commit adds a flag to use the pure coefficients instead
      of the processed ones (sce->coeffs). This is needed because
      IS will apply the changes to the coefficients immediately
      before the adjust_common_prediction function and it doesn't
      make sense to measure stereo channel coefficient difference
      when one of the channels coefficients are all zero.
      
      Therefore add a flag to use pure coefficients in that case.
      TNS is the only thing touching the coefficients before IS
      so common window prediction will not take that into account
      but the effect of the TNS filter per coefficient can be small
      (a few percent) so to some approximation it's fine to just
      ignore that.
      
      Also fixed a small error which doesn't alter the results
      that much. pow(sqrt(number), 3.0/4.0) == pow(number, 3.0/8.0) !=
      pow(number, 3.0/4.0).
      Signed-off-by: 's avatarRostislav Pehlivanov <atomnuker@gmail.com>
      4565611b
  10. 22 Aug, 2015 2 commits
  11. 21 Aug, 2015 1 commit
    • Rostislav Pehlivanov's avatar
      aaccoder: move the Intensity Stereo implementation out · d1ca7142
      Rostislav Pehlivanov authored
      This commit moves the intensity stereo implementation
      out from aaccoder and into a separate file. This was
      possible using the previous commits.
      
      This commit also drastically improves the IS implementation
      by making it phase invariant e.g. it will always choose the
      best possible phase regardless of whether M/S coding is on
      or most of the coefficients have identical phases.
      This also increases the quality and reduces any distortions
      introduced by enablind intensity stereo.
      
      Users are encouraged to test it out using the -aac_is 1
      parameter as it has always been.
      Signed-off-by: 's avatarRostislav Pehlivanov <atomnuker@gmail.com>
      d1ca7142