[MPlayer-dev-eng] Fast Forward and Slow Motion Patch

Struan Bartlett struan at NewsNow.co.uk
Fri Feb 14 17:34:30 CET 2003

Anders Johansson wrote:

>>Dear Arpi, Jonas, Fabian, et al,
>>Thanks for your positive feedback.
>>You've convinced me I need to at least mute the audio during fast 
>>forward / slow motion.
>>Myself, I didn't experience poor resyncing of A/V after reverting to 1x 
>>playback. After all, I'm just using the existing seek code, so I don't 
>>understand how it could be worse than unpatched code (I don't always get 
>>perfect A/V sync anyway!)
>>I'd love to attempt the reconfigured audio filters, but that job seemed 
>>much more difficult, as it I reckoned I would need to break out the 
>>audio filter config code into a separate function to avoid duplication.
>>I would like to try the muted audio and get back to you.
>I can help you get libaf to change the playback rate to fit the video
>speed, what do you need?
Thanks Anders - I would appreciate your help.

However, upon further consideration, I've been having second thoughts 
about the approach I've taken.

As to decreasing the video speed, I've successfully adjusted my patch to 
mute the audio during slow-motion. This works great for me seeing what's 
happening in high-speed kung-fu action scenes.

As to increasing the video speed, whereas simply increasing the playback 
speed works OK on my 800MHz PIII playing a scaled-down movie from the 
hard disk, I don't imagine it's going to work so well on slower PCs or 
when playing full-size movies from slow media. One member of this list 
reported that even 2x playback was "almost unplayable" on his PC.

But because I understand seeking is only possible between keyframes, if 
we want a smooth afast-forward, I imagine we need to be content to read, 
decode and apply every frame, although perhaps we can save CPU time by 
not writing every frame to the screen.

Either way, it would be great to speed up the audio playback rate in 
sync with the video. But first, I imagine a better algorithm for 
increasing video playback speed may be in order.

Best regds,


More information about the MPlayer-dev-eng mailing list