[vlc-devel] Re: vout questions

Sigmund Augdal sigmunau at stud.ntnu.no
Thu Sep 11 09:19:34 CEST 2003

On Thu, Sep 11, 2003 at 04:42:38AM +0000, j.zorko at att.net wrote:
> Hello, all ...
> I've some questions regarding the video output thread.  If someone who is intimate with this 
> code could answer them, i'd appreciate it!
> 1. Is there an mwait() or msleep() call that determines when to decode / display a picture, 
> analogous to the mwait() used to read from the source at the correct rate?  I've been looking for 
> this, to no avail.

There is a mwait() or msleep() call that determins when to display a
picture. It is in src/video_output/video_output.c in the RunThread() function.

> 2. The STATE_SLICE state in the libmpeg2 interface (libmpeg2.c) ... this seems to be where the 
> picture is timestamped, but why here?  Also, what is this 'picture_to_destroy' stuff?  I understand 
> a bit more about these parts of VLC than I did before, but i'm still mostly lost here.  Any 
> guidance would be wonderful ...

I don't know anything about this part, sorry.

> 3. The way I understand the late picture thing is this: if a picture is late, it's dropped before it's 
> rendered, so late pictures shouldn't make other consecutive pictures late.  However, i've an 
> instance where this is happening, so i'm trying to figure it out ...

There is also some code to skip a picture even before it is decoded. This is
in order to "catch up" when we are running late. I think it works best for
the libmpeg2 decoder at the moment, but I don't know how it works.
I've also seen vlc get stuck in "late picture skipped" messages, but I never
seen a general trend as to when this happens. What I do know is that using a
video filter (with --filter foo ) increases the frequncy of this phenomenon.

> 4. We're seeing a weird crash after playing an MPEG2 TS for 15-20 minutes, but only when we 
> ran VLC with --fullscreen.  Has anyone else noticed anything like this?

Don't know anything about this either. But I hope I was of some help.


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