The VideoLAN Forums

Hello,

I'm surprised that a good player like VLC does not contain any frame/step feature ?
Just want to display the previous or the next frame when the media is paused.
Maybe I didn't find out how to do this. But if it's not possible, why don't you guys add it to the next version of VLC.
I believe this is a must have feature for a video player...

Regards,

Link.

VLC does not support it and will not support it. There are 2 ways of writing a media player: frame based and time based. Both ways are not compatible with each. VLC is time based because of its streaming origins, so it doesn't know about the concept of frames (although it plays them obviously), so you can tell it to go certain seconds (or even milliseconds) back or forward, but you can't tell it to go to a specific frame.
On the contrary, MPlayer and QuickTime, etc. pp. are frame based, so they are able to do so.
Note that you can take video-snapshots in VLC anyway.

Once paused, couldn't you determine the frame rate of the movie, i.e. a dvd would usually be 24 fps, while quicktime movies would have that information embedded in), then provide a function to step back 1/fps of a second (i.e. 1/24 for a dvd).

If that's not accurately a frame, then there must be a way to decode the packet information to determine what portion is a frame, and display that, no? i.e. scan the bytes backward or forward til a signature 'frame break' is detected, then send that to the viewer.

Well, patches are already welcome. I don't think a member of the team will work on that, since this sounds like quite a big amount of work for a very little feature.

Well do you concede that its possible or that that would work?

Providing a function to go back an arbitrary amount of seconds doesn't seem like much work since the functions to do that must already be written...

In case that you just want to go back a known amount of seconds (or more precisely milliseconds), a working function exists already. The only thing that would have to be done is to calculate the new position or the time to go back. That's not hard at all.
What might be complicated is to pause directly after going backwards, so the previous frame is still displayed. But that's just a quick thought. I don't know whether this is a real problem.
To conclude: yes, this is possible, but I can't say exactly whether it is hard or not. This depends on the fact, whether you stumble across the way VLC is written or not.

...or just to go backwards X amount of data in the stream, and reset the image.

...or just to go backwards X amount of data in the stream, and reset the image.

Well, this would be more complicated than doing the same thing with the time, because you would have to take the bitrate of the specific streams into account as well. When seeking time-based, this isn't necessary.