1. 13 Jan, 2016 1 commit
    • Claudio Freire's avatar
      AAC encoder: fix assertion error with prediction · 2a31b076
      Claudio Freire authored
      Fixes an assertion error reported in #2686 that happens when
      using prediction (either explicitly or implicitly by setting
      the AAC main profile), since prediction code would allow
      creating new zeroes or removing existing ones, without
      properly checking for SF delta violations.
      
      This patch forbids creating/removing zeroes, perhaps an
      overly conservative approach, but a safe one. More permissive
      and sophisticated approaches may be attempted in the future.
      2a31b076
  2. 17 Oct, 2015 2 commits
  3. 12 Oct, 2015 1 commit
  4. 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
  5. 06 Sep, 2015 1 commit
  6. 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
  7. 29 Aug, 2015 1 commit
    • Rostislav Pehlivanov's avatar
      aacenc_pred: rework the way prediction is done · 44ddee94
      Rostislav Pehlivanov authored
      This commit completely alters the algorithm of prediction.
      The original commit which introduced prediction was completely
      incorrect to even remotely care about what the actual coefficients
      contain or whether any options were enabled. Not my actual fault.
      
      This commit treats prediction the way the decoder does and expects
      to do: like lossy encryption. Everything related to prediction now
      happens at the very end but just before quantization and encoding
      of coefficients. On the decoder side, prediction happens before
      anything has had a chance to even access the coefficients.
      
      Also the original implementation had problems because it actually
      touched the band_type of special bands which already had their
      scalefactor indices marked and it's a wonder the asserion wasn't
      triggered when transmitting those.
      
      Overall, this now drastically increases audio quality and you should
      think about enabling it if you don't plan on playing anything encoded
      on really old low power ultra-embedded devices since they might not
      support decoding of prediction or AAC-Main. Though the specifications
      were written ages ago and as times change so do the FLOPS.
      Signed-off-by: 's avatarRostislav Pehlivanov <atomnuker@gmail.com>
      44ddee94
  8. 22 Aug, 2015 1 commit
  9. 21 Aug, 2015 1 commit
    • Rostislav Pehlivanov's avatar
      aacenc: implement the complete AAC-Main profile · 76b81b10
      Rostislav Pehlivanov authored
      This commit finalizes AAC-Main profile encoding support
      by implementing all mandatory and optional tools available
      in the specifications and current decoders.
      
      The AAC-Main profile reqires that prediction support be
      present (although decoders don't require it to be enabled)
      for an encoder to be deemed capable of AAC-Main encoding,
      as well as TNS, PNS and IS, all of which were implemented
      with previous commits or earlier of this year.
      
      Users are encouraged to test the new functionality using either
      -profile:a aac_main or -aac_pred 1, the former of which will enable
      the prediction option by default and the latter will change the
      profile to AAC-Main. No other options shall be changed by enabling
      either, it's currently up to the users to decide what's best.
      
      The current implementation works best using M/S and/or IS,
      so users are also welcome to enable both options and any
      other options (TNS, PNS) for maximum quality.
      Signed-off-by: 's avatarRostislav Pehlivanov <atomnuker@gmail.com>
      76b81b10