VirtualDub doesn't play audio in preview

[Sebastian2011]

Hello, it would be great if someone could help me. I'm trying to edit an avi file with AviSynth and VirtualDub. If I open the avi directly in VDub, everything is fine. But when I play the same video via AviSynth in VDub, there is no audio. However, if I save a portion of it as avi, that avi does have audio, so apparently there is something wrong with the preview function.

The problem occurs with a minimal script like

AviSource("video.avi")

and also if I save the audio as wav and put

vid=AviSource("video.avi")
aud=WAVSource("audio.wav")
AudioDub(vid,aud)

in the avs file. No audio in the VDub preview. Of course I could load the wav via VDub "Audio from other file", but this wouldn't help me because then the cutting I do in AviSynth would only affect the video. Can anyone help?

[GideonK]

Hi, I open AviSynth scripts a lot in Vdub and never had your experience. Can you cut a small clip in Vdub and upload it so we can take a closer look?

[AlanHK]

In Vdub open the AVS and then do
File/File information and see what it says about the audio.

And also add info() to the script and see what Avisynth says.
How many channels?

Instead of Avisource, you can also use
FFmpegSource2("video.avi",atrack=-1,fpsnum=-1,fpsden=1)
or
DirectShowSource("video.avi")

These usually work if Avisource has a problem with audio.

[Sebastian2011]

Hi, I open AviSynth scripts a lot in Vdub and never had your experience. Can you cut a small clip in Vdub and upload it so we can take a closer look?

Here it is. Something must be wrong with the audio. I worked around the problem in the meantime by saving the audio as wav and re-encoding it, but I'd still like to know what caused the problem.

[Sebastian2011]

In Vdub open the AVS and then do
File/File information and see what it says about the audio.

Info looks normal, uncompressed PCM.

And also add info() to the script and see what Avisynth says.
How many channels?

It says 6 channels.

Instead of Avisource, you can also use
FFmpegSource2("video.avi",atrack=-1,fpsnum=-1,fpsden=1)
or
DirectShowSource("video.avi")

These usually work if Avisource has a problem with audio.

Interestingly, with FFMpegSource2, VDub says it finds no audio track. With DirectShowSource it works.

[hech54]

It opens and plays fine in VDub and AviDemux.

[hech54]

testcutvdub.avi
Here is a test cut I did in VDub....outputted it to H264 and kept the original audio.

[Sebastian2011]

testcutvdub.avi
Here is a test cut I did in VDub....outputted it to H264 and kept the original audio.

Thanks for everybody's efforts. Yes, opening it directly in VDub works fine for me too, trouble begins with AviSynth.

Another strange observation: As I said, when I open that file with AviSynth (AviSource) and VDub, it doesn't play the audio. If I go ahead and replace the "AviSource" in my script by "DirectShowSource" and reload, the sound is there. If I change the script back to AviSource, it's still there! But only until I close and reopen VirtualDub, then it's silent again.

So never mind and thanks again, it's just some kind of bug.

[AlanHK]

It says 6 channels.

That's the issue; I think it's just VDub isn't set up for multichannel playing.

If you want to hear your clip, you can just do

AVISource("test.avi")
GetChannel(3)

which will give you Channel 3, the centre channel, voice in your clip.

When you have your script done you can comment out the GetChannel and save the output as multichannel, even if you don't hear it in VDub.

Or if you want to downmix 6 channels properly to stereo, use a function like

function Dmix6Dpl(clip a)
{
  flr = GetChannel(a, 1, 2)
  fcc = GetChannel(a, 3, 3)
  lrc = MixAudio(flr, fcc, 0.3205, 0.2265)
  bl  = GetChannel(a, 5)
  br  = GetChannel(a, 6)
  sl  = MixAudio(bl, br, 0.2265, 0.2265)
  sr  = MixAudio(bl, br, -0.2265, -0.2265)
  blr = MergeChannels(sl, sr)
  return MixAudio(lrc, blr, 1.0, 1.0)
}

See
http://avisynth.org/mediawiki/GetChannel
and
http://forum.doom9.org/showthread.php?p=1243880#post1243880

If I go ahead and replace the "AviSource" in my script by "DirectShowSource" and reload, the sound is there.

DirectShowSource uses your usual Windows codecs to play it, probably ffdshow.
That will downmix it for you, if your PC is set up for stereo.

[hech54]

....or just drag the file into VDub and stop fvkking around with AviSynth when it isn't necessary.

[poisondeathray]

That's the issue; I think it's just VDub isn't set up for multichannel playing.

Then why would loading the AVI directly with 6 channel audio play ?

[hech54]

That's the issue; I think it's just VDub isn't set up for multichannel playing.

Then why would loading the AVI directly with 6 channel audio play ?

I didn't think it was either to be honest.

[davexnet]

To downmix to 2-channel, I usually use directshowsource for 6-channel ac3.
FFDshow's mixer does a very good 2-channel downmix.

[AlanHK]

That's the issue; I think it's just VDub isn't set up for multichannel playing.

Then why would loading the AVI directly with 6 channel audio play ?

Dunno why, but via Avisynth and VDub multi channel doesn't work, at least on my setup, and apparently the OP's.
I downmix everything to stereo, since that's all I have anyway, so I don't really worry about it.

[Sebastian2011]

That's the issue; I think it's just VDub isn't set up for multichannel playing.

Then why would loading the AVI directly with 6 channel audio play ?

Dunno why, but via Avisynth and VDub multi channel doesn't work, at least on my setup, and apparently the OP's.
I downmix everything to stereo, since that's all I have anyway, so I don't really worry about it.

Thanks a lot, that helped! Since the source is a DVD, I tried again to use .d2v and .ac3 out of DGIndex files via AviSynth, which resulted in the same problem. When I used GetChannel(3), I got audio, but the music was missing. So I downmixed the .ac3 to stereo .wav with BeLight and used that one. Now everything's shiny.

[Sebastian2011]

....or just drag the file into VDub and stop fvkking around with AviSynth when it isn't necessary.

I use AviSynth to cut, join and fade in/out.

[hech54]

VDub and AviDemux do all I need....and they open my files WITH AUDIO every time.

[AlanHK]

Thanks a lot, that helped! Since the source is a DVD, I tried again to use .d2v and .ac3 out of DGIndex files via AviSynth, which resulted in the same problem. When I used GetChannel(3), I got audio, but the music was missing. So I downmixed the .ac3 to stereo .wav with BeLight and used that one. Now everything's shiny.

Simpler to downmix in Avisynth:

Best is to put the downmix functions on an avsi file in your Avisynth plugins folder, then you can call them like any built in function.
Otherwise, just put the function in the same file:

AVISource("test.avi")
Dmix6Dpl()

#Downmix Dolby pro-logic 6 channels to stereo 
function Dmix6Dpl(clip a)
{
  flr = GetChannel(a, 1, 2)
  fcc = GetChannel(a, 3, 3)
  lrc = MixAudio(flr, fcc, 0.3205, 0.2265)
  bl  = GetChannel(a, 5)
  br  = GetChannel(a, 6)
  sl  = MixAudio(bl, br, 0.2265, 0.2265)
  sr  = MixAudio(bl, br, -0.2265, -0.2265)
  blr = MergeChannels(sl, sr)
  return MixAudio(lrc, blr, 1.0, 1.0)
}

[Sebastian2011]

Thanks a lot, that helped! Since the source is a DVD, I tried again to use .d2v and .ac3 out of DGIndex files via AviSynth, which resulted in the same problem. When I used GetChannel(3), I got audio, but the music was missing. So I downmixed the .ac3 to stereo .wav with BeLight and used that one. Now everything's shiny.

Simpler to downmix in Avisynth:

Best is to put the downmix functions on an avsi file in your Avisynth plugins folder, then you can call them like any built in function.
Otherwise, just put the function in the same file:

AVISource("test.avi")
Dmix6Dpl()

#Downmix Dolby pro-logic 6 channels to stereo 
function Dmix6Dpl(clip a)
{
  flr = GetChannel(a, 1, 2)
  fcc = GetChannel(a, 3, 3)
  lrc = MixAudio(flr, fcc, 0.3205, 0.2265)
  bl  = GetChannel(a, 5)
  br  = GetChannel(a, 6)
  sl  = MixAudio(bl, br, 0.2265, 0.2265)
  sr  = MixAudio(bl, br, -0.2265, -0.2265)
  blr = MergeChannels(sl, sr)
  return MixAudio(lrc, blr, 1.0, 1.0)
}

Thanks a lot, it works fine and is indeed easier! Sorry for the late reply, I just didn't get around to it sooner. May I ask, is the function automatically applied to all clips if there are multiple ones? Is the "clip" in the function name a custom name or is it part of the syntax?

[Gavino]

May I ask, is the function automatically applied to all clips if there are multiple ones? Is the "clip" in the function name a custom name or is it part of the syntax?

The function is not applied automatically, and has to be explicitly called in order to be applied to some clip.
Here the line Dmix6Dpl() is calling the function - since no clip is explicitly mentioned, the call is implicitly applied to the result of the previous operation (the source clip from AVISource()).

"clip" in the function definition is the type of the parameter 'a'.
For more details on Avisynth script functions, see
http://avisynth.org/mediawiki/User_defined_script_functions

[Sebastian2011]

May I ask, is the function automatically applied to all clips if there are multiple ones? Is the "clip" in the function name a custom name or is it part of the syntax?

The function is not applied automatically, and has to be explicitly called in order to be applied to some clip.
Here the line Dmix6Dpl() is calling the function - since no clip is explicitly mentioned, the call is implicitly applied to the result of the previous operation (the source clip from AVISource()).

"clip" in the function definition is the type of the parameter 'a'.
For more details on Avisynth script functions, see
http://avisynth.org/mediawiki/User_defined_script_functions

To the result of the previous operation, that answers it, thanks! I wasn't sure whether "clip" was a specific clip to apply the function to.