Megui AC3 5.1 to AAC DPLII normalize one channel only

[XMEN3]

With downmix stereo both channels are normalized equally but with DPLII the left channels remains low.
Same accours with ac3 DPLII output.

Installed avisinth 2.5.8 with x64 mod by JoshyD but is releated to this ac3 only, other ac3 5.1 are downmixed and normalized fine using DPLII.

http://forum.doom9.org/showthread.php?t=152800

Below you can see waveforms.
The source ac3 sample can be downloaded.
Converting to 3 stereo waves i can see regular CLFE FLFR and SLSR tracks.


Script from megui log for downmix stereo.

--[Information] [20/03/2012 20:26:43] Trying to open the file with NicAudio
--[Information] [20/03/2012 20:26:43] Successfully opened the file with NicAudio
--[Information] [20/03/2012 20:26:43] Avisynth script
---[NoImage] LoadPlugin("C:\Program Files\Megui_x64\tools\avisynth_plugin\NicAudio.dll")
---[NoImage] NicAc3Source("D:\sample.ac3")
---[NoImage] # detected channels: 6 channels
---[NoImage] # detected channel positions: 3/2/0.1
---[NoImage] c6_stereo(ConvertAudioToFloat(last))
---[NoImage] Normalize()
---[NoImage] return last
---[NoImage] # 5.1 Channels L,R,C,LFE,SL,SR -> stereo + LFE
---[NoImage] function c6_stereo(clip a)
---[NoImage] {
---[NoImage] fl = GetChannel(a, 1)
---[NoImage] fr = GetChannel(a, 2)
---[NoImage] fc = GetChannel(a, 3)
---[NoImage] lf = GetChannel(a, 4)
---[NoImage] sl = GetChannel(a, 5)
---[NoImage] sr = GetChannel(a, 6)
---[NoImage] fl_sl = MixAudio(fl, sl, 0.2929, 0.2929)
---[NoImage] fr_sr = MixAudio(fr, sr, 0.2929, 0.2929)
---[NoImage] fc_lf = MixAudio(fc, lf, 0.2071, 0.2071)
---[NoImage] l = MixAudio(fl_sl, fc_lf, 1.0, 1.0)
---[NoImage] r = MixAudio(fr_sr, fc_lf, 1.0, 1.0)
---[NoImage] return MergeChannels(l, r)
---[NoImage] }
...
--[Information] [20/03/2012 20:26:43] Commandline used: -ignorelength -lc -q 0.35 -if - -of "{0}"

Script used by megui for downmix DPLII.

--[Information] [20/03/2012 20:26:48] Trying to open the file with NicAudio
--[Information] [20/03/2012 20:26:48] Successfully opened the file with NicAudio
--[Information] [20/03/2012 20:26:48] Avisynth script
---[NoImage] LoadPlugin("C:\Program Files\Megui_x64\tools\avisynth_plugin\NicAudio.dll")
---[NoImage] NicAc3Source("D:\sample.ac3")
---[NoImage] # detected channels: 6 channels
---[NoImage] # detected channel positions: 3/2/0.1
---[NoImage] c6_dpl2(ConvertAudioToFloat(last))
---[NoImage] Normalize()
---[NoImage] return last

---[NoImage] # 5.1 Channels L,R,C,LFE,SL,SR -> Dolby ProLogic II
---[NoImage] function c6_dpl2(clip a)
---[NoImage] {
---[NoImage] fl = GetChannel(a, 1)
---[NoImage] fr = GetChannel(a, 2)
---[NoImage] fc = GetChannel(a, 3)
---[NoImage] sl = GetChannel(a, 5)
---[NoImage] sr = GetChannel(a, 6)
---[NoImage] ssl = MixAudio(sl, sr, 0.2818, 0.1627)
---[NoImage] ssr = MixAudio(sl, sr, -0.1627, -0.2818)
---[NoImage] fl_fc = MixAudio(fl, fc, 0.3254, 0.2301)
---[NoImage] fr_fc = MixAudio(fr, fc, 0.3254, 0.2301)
---[NoImage] l = MixAudio(fl_fc, ssl, 1.0, 1.0)
---[NoImage] r = MixAudio(fr_fc, ssr, 1.0, 1.0)
---[NoImage] return MergeChannels(l, r)
---[NoImage] }

http://img94.imageshack.us/img94/4954/samplead.png (http://imageshack.us/photo/my-images/94/samplead.png/)

Sample:

http://www.mediafire.com/?sodfl2y6r2xb0cy (http://www.mediafire.com/?sodfl2y6r2xb0cy)

[tebasuna51]

The problem occurs when the ac3 isn't Dolby Digital compliant, because the surround channels aren't 90º phase shifted.

You can use Foobar2000 with foo_dsp_downmix plugin and select Enabled in 90º Phase Shifting to obtain a correct dpl II downmix.

[XMEN3]

Thanks.