anchor.diff:      };
       # master
       "1.999" = {
  -      fetchzipversion = 5;
  -      version = "2018-01-12";
  -      rev = "f915e6d4afafabed8281b172f93502acbe101f3a";
  -      sha256 = "137725fe8510ca855da293bd1794a9500aeaf90d34c01e323f992af560dc6769";
  +      fetchzipversion = 6;
  +      version = "2019-02-14";
  +      rev = "a90944ce794986d8c0daab1449903909ba1956a7";
  +      sha256 = "6105b5dd27461da34d96fc0416530ee197140ac31f60f847f849e0f9eef065ac";
       };
     };
     source = sources."${channel}";
  
positive.code:       || experimentalFpMbStatsSupport
        || experimentalEmulateHardwareSupport)}-experimental"
    ] # Experimental features
      ++ optional experimentalSpatialSvcSupport "--enable-spatial-svc"
      ++ optional experimentalFpMbStatsSupport "--enable-fp-mb-stats"
      ++ optional experimentalEmulateHardwareSupport "--enable-emulate-hardware"
      ++ optional experimentalMiscFixes "--enable-misc-fixes";
  
    meta = with lib; {
  
negative.code:     "--${boolEn multiResEncodingSupport}-multi-res-encoding"
      "--${boolEn temporalDenoisingSupport}-temporal-denoising"
      "--${boolEn temporalDenoisingSupport}-vp9-temporal-denoising"
      (newFlag "1.8" "--${boolEn consistentRecodeSupport}-consistent-recode")
      "--${boolEn coefficientRangeCheckingSupport}-coefficient-range-checking"
      "--${boolEn betterHWCompatibility}-better-hw-compatibility"
      "--${boolEn (elem targetSystem platforms.bit64)}-vp9-highbitdepth"
  