Precision when seeking

[lobster]

I need a player that is very precise when seeking. Is VLC the wrong choice?

For example: the movie is paused and a call to libvlc_media_player_get_time is made. After that, a call to libvlc_media_player_set_time. Now the movie actually moves forward in time - when it should be standing still?

It also appears that libvlc_media_player_set_time doesn't seek to the exact same frame every time. I need that. If set_time is called while the movie plays, it tends to skip a bit of the audio from where it is positioned. The audio seems fine if paused, set and then played from that position.

I am working with avi/xvid files. Can something be done?

Another thing: if many calls are made too quickly to libvlc_media_player_next_frame, it just freezes.

[Jean-Baptiste Kempf]

Yes, VLC is not very precise in seeking.

[tmoran]

I start playing, wait 2 seconds, then use libvlc_media_player_set_time(44000) to go to the 44 second point. A call on libvlc_media_player_get_time returns 44000.
Then I wait another two seconds and call libvlc_media_player_get_time and it returns 36368, which appears to match the actual time of the video I see on the screen.
Doing this with different numbers than 44000, it always seems to seek to several seconds early. Is that perhaps due to something controllable (caching?) Or is libvlc_media_player_set_time inherently just a vague approximation of the desired point?

[Rémi Denis-Courmont]

It depends on the file format.

[Zingaro2002]

In you experience, what are the most precise-seeking file formats?

I am transcoding live streams (audio and video) to files (using libvlc and sout option), so I can choose codec and container for my files; what is your advice about them?
I absolutely need a good precision in seeking when I re-view those files (I mean: an error of 1 second is ok, not too much more).

[Jean-Baptiste Kempf]

mkv or mp4, probably.

[tmoran]

>> In you experience, what are the most precise-seeking file formats?
>mkv or mp4, probably.
The file I was trying, that went to :36 instead of :44, was an mp4. So it sounds like some experimentation is needed.

[Sébastien Escudier]

did you try with VLC directly ? like :
vlc my_movie.mp4 --start-time=10
It is precise here.

[tmoran]

> vlc myfile.mp4 --start-time=10
Also very far off. But the same command run with an old (0.8.6i) vlc worked correctly.

[Sébastien Escudier]

would you have a sample ?
mp4 is very precise for me.

[tmoran]

Oops, you are right. I checked the file labeled .mp4 but it was actually mpeg, according to ffmpeg. A file that is truly mp4 does seems to be accurate about start-time, while the mpeg one is wrong. This is with the new vlc 2.0
The old vlc 0.8.6i was accurate for both files (though its video was corrupt for the mp4 file).

[Rémi Denis-Courmont]

MPEG PS seeking was never accurate. That file format provides no indexing. Try to seek fast and accurately with your living room DVD player if you do not trust me...

[sparkz]

I was a little disappointed when I found out the "set_time" feature doesn't work that well.

I'm using WMP via MCI for a video library application. With WMP I step through my videos at fixed intervals, taking snapshots, to make an index card. It works very fast with WMP and accurately as far as I can tell. The only only downside is that it won't handle MP4 files via MCI.

So I've been trying VLC which works fine as far as the API goes. However using the same files which worked fine under WMP are slow to position under VLC and not very accurate. Where in WMP I can do it to the frame give or take one. In VLC, with the same files, it's slow to position and way out on accuracy. Although I did notice MP4 files were better, usually within the second although much slower to get there.

I can appreciate the challenges when doing this and the lack of proper indexing must make it difficult. There must be a better way of doing this if WMP can do it though?

Don't get me wrong me wrong. I think VLC is a great program, probably the best WMP alternative out there. The less Microsoft programs I use the better I feel. Just VLC seems lacking in this department.

Regards
Mark

[sparkz]

Is there any chance of having a new state so that when it's still trying to work out the position you can tell from the current state?

Currently, if I set a time and get the time back it just has the same time I just set. However after a few seconds this has usually changed so it's obviously still seeking. It would be great if it was possible to tell when it has finished seeking.

I did try looking at the stats but that doesn't seem to change between after the "set_time" and when the picture has finally settled.

Also, is there any way of speeding this up so it's as good as WMP? With WMP I get almost instant positioning and even if it's not it's easy to check when it's ready.

[freesunshine]

set gop to a small value like 12 would make it better; gop=12 provides a 12/fps second Accuracy。

[sparkz]

Thanks I'll try that.

I assume that's the command:
#sout-switcher-gop=