[Mplayer-users] changing audio playback rate

[Oskar Liljeblad]

On Wednesday, April 18, 2001 at 03:48, Arpi wrote:
> > > > Hi... I recently came across a DivX (DIV3) video with MPEG layer-3 audio
> > > > that plays at an incorrect framerate... It is reported as 23.98 fps
> > > > but should be played at 27-30 fps. I fixed this with -fps 30 but
> > > > unfortunately this does not change the audio playback rate.
> > > > Can this be changed as well? (Let me know if you need the .avi file)

> > > Isn't the problem is 44khz vs 48khz audio? (48khz in file, but soundcard is
> > > limited to 44?)
> > 
> > Yeah, that's likely - it's a Creative SB64 Gold (ISA PnP)...
> > Any way to fix that in software? I'm using linux OSS drivers right
> > now... (no alsa)

> Not yet. We'll move to libxmm, it supports (or at least will support) 
> downsampling.
> Currently the only way is changing the card :)

I just checked with another 48000 Hz audio DivX, no problems with that one.
So it seems related to these DivX files in particular... I did some manual
timing (with a stopwatch) too see how many frames elapsed during a physical
minute. I found it to be 22, instead of 24 as reported by the file!

physical      mplayer
time          output
00:00:00   => A:   2.7  V:   2.7  A-V:  0.002  ct: -0.007   66  37%   5%  5.8% 
00:01:00   => A:  57.6  V:  57.6  A-V:  0.002  ct: -0.025  1381  29%   5%  5.0% 

Notice that the difference in time according to mplayer is 57.6 - 2.7 = 54.9 seconds.
Multiply this by the initiallity reported framerate (24) and you'll get:

  (57.6 - 2.7) * 24 = 1317.6

A striking similarity between the frame index at those two times:

  1381 - 66 = 1315

My guess would be that mplayer has messed up timing somehow...
Xine plays the audio correctly (!), but without image...

Want a piece of the DivX file?

Oskar Liljeblad (osk at hem.passagen.se)

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