Topic: XMPlay AC3 plugin

[Sebastian Andersson]

I have finished an AC3 input plugin for XMPlay which is available here:

http://www.un4seen.com/filez/2/xmp-ac3.zip

It should support all the usual stuff like playing, pausing, seeking... but currently lacks ReplayGain, tags and streaming support. Please report any bugs and issues in this thread.

[Sebastian Andersson]

I've uploaded a minor update with a more precise AC3 file verification. The plugin is now also compressed with Petite.

[Tsorovan]

Thank you sir!

[Sebastian Andersson]

Thank you sir!

Heh.

[Sebastian Andersson]

I updated the plugin once again. The update is minor and related to optimization/speed.

[Sebastian Andersson]

xmp-ac3 has been updated once again. It will default to 5.1 at a "clean" plugin install stage, and a few improvements in terms of speed have been made. This is the final release for xmp-ac3.

[Mr_Rabid_Teddybear]

Issue with latest xmp-ac3:
When I try to drag and drop a bunch (e.g. one album) of files or a m3u playlist referring to an album of other formats than ogg or mp3 onto xmplay, xmplay crashes immediately and every time with xmp-ac3 active. Tested with mpc, flac, m4a (native plugins) and shn (Winamp plugin). As mentioned, Ogg Vorbis and mp3 are not affected.
The Windows crashmessage tells:

Error signature
AppName: xmplay.exe  AppVer:3.2.0.6  ModName: xmp-ac3.dll
ModVer: 0.0.0.0  Offset: 00001256

Deactivating xmp-ac3 fixes the issue.
I've extracted the infoblock relevant to latest crash from drwtsn32.log and pasted it into a xmp-ac3-crash.txt, which I've uploaded to  ftp.un4seen.com/incoming/

[Sebastian Andersson]

I haven't got access to the upload FTP, but here's an update to try with...

     http://www.un4seen.com/filez/2/xmp-ac3.dll

[Mr_Rabid_Teddybear]

Don't seem to help. Anyway, I sendt the crashlog to sebastian.andersson x gmail x com

[Tsorovan]

Yeah, I get this too. Update doesn't help. It happens with dirs that I add that don't even have AC3 files too, like FLAC. Disabling this plugin removes the problem. It seems .m3u or possibly .cue files might do it.

[Sebastian Andersson]

I've uploaded an update. The file verification process is slightly different, and I tested with a few AC3/M3U files without any crash.

Edit: By the way, the issue was sorted for Teddybear when I sent him an uncompressed version of xmp-ac3. If this update doesn't help, I might send you one, too.

[Mr_Rabid_Teddybear]

I've uploaded an update. The file verification process is slightly different, and I tested with a few AC3/M3U files without any crash.

Edit: By the way, the issue was sorted for Teddybear when I sent him an uncompressed version of xmp-ac3. If this update doesn't help, I might send you one, too.

Yes. Now I've briefly tested this new compressed version, and it seems I'm also not able to provoke such a crash with this version. I'll let you know if anything more happens.....

[SmartOne]

I've noticed clipping while using this plugin.  There's less with the Dynamic range compression option checked, but I shouldn't have to compress the dynamic range... 

What exactly do each of the output settings do?  For example, what's the difference between 5.1 and Dolby?

[Dotpitch]

What exactly do each of the output settings do?  For example, what's the difference between 5.1 and Dolby?

I guess 5.1 is 5.1 PCM output, while Dolby output a stream for an external Dolby decoder?

I've noticed clipping while using this plugin.  There's less with the Dynamic range compression option checked, but I shouldn't have to compress the dynamic range...

Are you sure the problem is with the plugin and not with the file? Try decoding it using AZID.

[SmartOne]

I guess 5.1 is 5.1 PCM output, while Dolby output a stream for an external Dolby decoder?

That's what I thought, but why does a Dolby 2-channel AC3 (Pro Logic or otherwise...) set to 5.1 only come out of the left channel (headphones) but plays "normally" (both channels) when set to Dolby?  The Stereo setting also sounds "normal," but I'm not 100% sure it sounds the same as Dolby  The Stereo setting has inferior panning compared to Dolby.  Dolby should contain the Dolby metadata for later decoding, but Stereo should be the exact same information represented as Linear PCM.  

All of this is using DirectSound.
  
Here's a file to test the left channel issue with 5.1:
Beyond the Walls: http://www.mediafire.com/?ndmmiqy5ywn

Here's a better file to test differences in panning (the trombone section is panned farther left than the bass trombone at about 0:50 with Dolby, Stereo squishes them all to the far left):
Hunting Wabbits: http://www.mediafire.com/?zweqgjq2ymt
 

Are you sure the problem is with the plugin and not with the file? Try decoding it using AZID.

I suspect Hunting Wabbits does have a small amount of clipping, but since I hear less with Dynamic range compression checked, that suggests the plugin affects the quality.  Check out the trombone solo at about 2:20 without compression.  Clipping to the max.  Turn compression on.  Clipping greatly reduced.

[Dotpitch]

I suspect Hunting Wabbits does have a small amount of clipping, but since I hear less with Dynamic range compression checked, that suggests the plugin affects the quality.  Check out the trombone solo at about 2:20 without compression.  Clipping to the max.  Turn compression on.  Clipping greatly reduced.

The left and right channel certainly have a lot of clipping, their encoding volume is just too high (+0.7 and +0.8 dB respectively). The clipping might have been in the source file, but I've seen non-commercial encoders (like Aften) produce clipped AC3s from normalized files as well. DRC values are inserted in the AC3 stream at the encoding stage to notify the decoder of the loudness of a certain block of audio, so the decoder can decide to add a gain to avoid too loud or too quiet sounds before the audio is fully decoded. DRC is intended to be used in noisy environments or with a weak audio system, so you can switch it off if you don't like the sound it produces.

That's what I thought, but why does a Dolby 2-channel AC3 (Pro Logic or otherwise...) set to 5.1 only come out of the left channel (headphones) but plays "normally" (both channels) when set to Dolby?

That sounds more like a channel mapping problem. Is the right channel by coincidence present on the center connection of your soundcard?

The Stereo setting has inferior panning compared to Dolby.  Dolby should contain the Dolby metadata for later decoding, but Stereo should be the exact same information represented as Linear PCM.

Is that with a 5.1 file or a stereo one? For 5.1, different downmixing coefficients for center and surround channels can produce different panning.

By the way, if you want some more configuration options, substitute xmp-ac3 with WinampAC3.

[Ian @ un4seen]

I've noticed clipping while using this plugin.  There's less with the Dynamic range compression option checked, but I shouldn't have to compress the dynamic range... 

What exactly do each of the output settings do?  For example, what's the difference between 5.1 and Dolby?

What version of the AC3 plugin are you using? I don't see these options

[Dotpitch]

What version of the AC3 plugin are you using? I don't see these options

The one from the Support Site. Had to do a search to find out why the options were taken out.

The AC3 plugin dates back to 2005, before the XMPlay settings were moved to the XMPLAY.INI file. I don't think the AC3 options are even needed anymore, as XMPlay has built-in downmixing, so I've put up an updated build without them... xmp-ac3

I've also put up another AC3 plugin update with support for internet streaming.

[SmartOne]

Don't throw away that old plugin just yet!    The new version (rev. 1) resolves the "added clipping" problem, but the panning is bad.  The trombones are crammed into the far left again, and there are no options to play with this time.

Hunting Wabbits is 6-channel.  What performs the downmixing if Downmix multi-channel isn't checked within XMPlay?  DirectSound?  Does it sound different?  Is the quality different?

A new version of the plugin could possibly incorporate the "Dolby" panning behavior of the old but retain proper channel levels.  That seems optimal...  By the way, the Dolby setting outputs stereo, for some reason.  Maybe it was intended for Pro Logic type stuff.

WinampAC3 seems to have the same panning as the new XMPlay plugin...  The old Dolby setting was probably Pro Logic handling which actually resulted in better panning (in some cases?)

[Ian @ un4seen]

I think the difference you're hearing is due to Dolby Surround/ProLogic having a single rear/surround channel, so the left and right rear channels get combined and anything that was rear-left or rear-right becomes rear-centre. Btw, has anyone confirmed whether the old plugin's Dolby mix can be decoded back to the 4 (left/right/centre/rear) channels? Does anyone know of any software that can take a Dolby mix and spit out the decoded channels, eg. to WAV file(s)?

Regarding down-mixing, when not enabled in XMPlay, that will be performed (if necessary) by Windows or the driver (with hardware mixing). Windows' down-mixing will be similar to XMPlay's, but drivers could add some fancy effects to it.