Old 11th October 2005, 02:10   #1
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SPDIF Passthrough

Please include an option in the Directsound output plug-in or a whole new output plugin allowing SPDIF passthrough for the best sound quality for Winamp users with audio receivers and a nice speaker setup. Thanks!
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Old 11th October 2005, 03:26   #2
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Doesn't that automatically take place? I've understood that winamp passes a stream of digital audio to windows which will push it right out the spdif port? I could be wrong of course.
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Old 11th March 2010, 23:07   #3
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I think he's right.

I think he's right, winamp is doing something with the audio data that's preventing SPDIF pass through.

I'm trying to use ffdshow to encode SPDIF audio. I use the Direct show in plugin to pass the audio to ffdshow. Everything works, but when I enable AC3 encoding, I get nothing but garbled sound. I noticed the AC3 plugin outputs it's audio directly to direct sound by passing winamp. Is there a way at least to get the in_dshow plugin to do the same? Or would it be more sane to recode the Direct Sound output plugin to support SPDIF/AC3 passthrough?

I should also state that ffdshow is working with most other players just fine and encoding AC3 just fine as well. Right now I'm left with playing my audio through media player classic, as I can't get Windows Media Player to let FFDShow touch any MP3 audio data. What I'm saying here is the alternatives for playing mp3's with AC3/SPDIF out are grim, and I'd like to see winamp be the first player to properly support this for those of us with digital speakers.
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Old 12th March 2010, 13:58   #4
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Switch off equalizer, switch off replaygain. Disable any DSP plugins. Switch on "allow 24-bit sound" and disable surround sound. Turn Winamp's volume to 100%. Turn balance to the middle.

Doing so should result in the bitstream being passed through untouchedly.

I didn't try it for myself yet, as my PC doesn't have a S/PDIF output. I'd be glad if you could test it and let me know it that works for you!

Best regards,
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Old 26th September 2010, 17:13   #5
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I found some time now to test that, as I wanted to play some AC3 5.1 sound through my home theater receiver via Winamp.

And unfortunately, it turns out that there is NO WAY to accomplish that. Even when I disable all processing options (EQ, dither, volume control etc.) Winamp seems to touch the S/PDIF data coming from AC3filter before sending it to the DirectSound output.

All I get is fragments, noise, and a flickering "Double D" indicator on my home theater system (indicating that it cannot sync to any valid AC3 stream).

When I play the same file through WMP or other players, it works very well.

AC3Filter is set to passthrough the AC3 to S/PDIF.

But it seems that Winamp doesn't use sound output in in_dshow.dll (by just inserting the audio renderer at the end of in_dshow's Graph).

Instead I think the audio output of in_dshow.dll is taken back into Winamp by winamp.exe as the host application and then sending it to out_ds.dll, which itself has its own graph for the audio and sends the sound to the Audio renderer.

And exactly there is the break. Winamp just doesn't manage leaving the stream UNTOUCHED and intact!

Are my findings correct?

Maybe this could be fixed in one of the next versions? I think out_ds.dll is the module to be looked into... Thanks, developers!!!

Best regards,
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Old 6th January 2011, 10:12   #6
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Just thinking of it 'cause I'm reading another, related thread right now --- is there anything new on this here?
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Old 13th January 2011, 20:25   #7
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I know I helped someone get this working the other day with a specifically coded DTS file. Can't remember what I did, but I'll locate the thread and post back in a minute...

Edit: Here it is. A little different to what you are asking, but may well give you a result.


My Onkyo is connected to the Creative X-Fi using SPDIF on XP and all works fine for me to play my FLAC\MP3s\etc.

And when I fiddled as per that thread, I got DTS 5.1 surround movies coming out in full.
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Old 3rd August 2011, 00:37   #8
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As I understand, Winamp wasn't designed to pass untouched audio.

It has plugin system with an SDK that allows us to develop input plugins to early process the reading stream, pass its result to Winamp process the wave audio, and then sends it to the output plugin to send the resulting wave audio somewhere. In the middle of it, Winamp does stuff with that audio, like equalizer, volume, etc.

It totally breaks Winamp design if an input plugin gets the audio and sends it elsewhere, as if it was an output plugin. Therefore, passthrough with Winamp can't work.

Of course, I understand some ppl might wanna use Winamp's UI to make a playlist and show tag info, but doesn't want Winamp effectivelly touching the audio, but that's not what Winamp's devs wanted.

Otherwise, if you wanna use passthrough, you might wanna use some simpler player, like a DirectShow (Media Player Classic suggested) and use AC3Filter, that does it nicely.

Just remember that musics are 2.0, so SPDIF can send it as PCM, no need to encode it to AC3 and lose quality. Realtek driver for exemple supports sending PCM 24bit 192KHz over SPDIF, as long as it's 2.0.

Also, using DirectShow provides us a great advantage: it muxes multiple audio sources into the same stream. If we use passthrough, only 1 app can use a sound device and all otehrs get muted.
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