Strange sound behavior

[mica]

OS: Windows XP
VLC: 0.7.0

Computer specifications:
AMD Duron 1000@1187MHz
256MB SDRAM
Asus A7V133-C
Nvidia Geforce4 TI 4800SE
SoundBlaster 128 PCI+
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When I'm playing video files I quite often experience strange sound behavior. The sound "goes down", it doesn't sound the way it should. Then again, after a while it's normal. It sounds a bit like some kind of slow motion thing (like some movie with a slow motion scene where also sound gets slower). Quite hard to explain.

I have had this problem especially with SVCD files (which are in this case mostly music videos, so I can hear the this-doesn't-sound-right -thing clearly), but it seems to occur with files in other formats too, at least when jumping from one location to another in the video.

When this thing happens suddenly while playing some video, i get this error in the messages window (the values are different every time):

main warning: output date isn't PTS date, requesting resampling (-40020)
main warning: buffer is 40012 in advance, triggering downsampling
main warning: resampling stopped after 4258296 usec

The problem seems to occur on different playback times in different locations, so i don't think it happens because the video is broken or anything, and with other media players the problem doesn't exist.

I hope you understood what I'm trying to say :)
Help would be appreciated.

Thank You.

[Quaoar]

For the record, I get exactly the same behaviour using VLC 0.7.0 under Windows ME.

I also think there is something suspect about all the "output date isn't PTS date" messages. At first I thought it was a streaming problem, but it happens on playback of files as well.

[mica]

So we are the only ones with this problem?

[Gibalou]

This problem is a direct consequence of the way VLC synchronises the playing rate of a video/audio.
VLC was originally designed as a network player so the playing rate is synchronised on the intended playing speed while most other software synchronise the playing rate on the local audio/soundcard playing rate.

These 2 rates are never quite identical so VLC will occasionnaly resample the audio if it notices the soundcards playing rate drifts from the intended playing rate.

While this concept is really important when playing network sources where the data is pushed to the client, it is kindof useless for playling local content so we are planning to remedy this but that will take some time to be implemented.

[Raymond]

I also have this problem when playing not-so-perfect mpg files (from VCDs).

However, quicktime/mplayer plays those files fine.

Weird.

[Raymond]

Also, I'm currently using the VLC as a VCD player and no other players seems to be able to do that, as it has the option to play it on external screens, disable left/right audio channels, fast fullscreen switch and so on.

You can even use VLC to play karaoke files....that's, erm, if this problem didn't persist.

As a side-note, most of the VCDs on the market do not have perfectly encoded mpgs, that's why most vcd players have error correction.

It is true that VLC plays perfectly encoded mpgs perfectly, but the synchronisation issue really hurts when you play MTVs.

Those not-so-perfect files seem to play fine on QuickTime and MPlayer, but then those players do not have the functionalities of VLC...

aaaAARRRHHH.....dilemmas.....

Is this issue hard to fix?

[Quaoar]

This problem is a direct consequence of the way VLC synchronises the playing rate of a video/audio.

I thought I would re-visit this thread. In general I find this problem to be only a very minor issue. But just recently I've been using VLC to listen to the ogg stream from University Radio Nottingham and I'm finding that the sound "wobble" (resampling) is particularly pronounced when I'm listening to this ogg stream.

http://live.urn1350.net:8080/urn_high.ogg

Maybe this problem is confined to the Windows port of VLC? I'm inclined to think that the behaviour of the Windows scheduler also plays some kind of role?