Problem with frame accuracy using nextFrame() with GStreamer

[fakob]

Hi
I am looking for an accurate way of jumping frame by frame within a video forwards and backwards with ofGstVideoPlayer.
Using nextFrame() and previousFrame() with some videos some frames are being skipped (that is probably codecs and I-frames related?).
For the nextFrame() I found a way using gst_event_new_step, but I have not achieved an equivalent for previousFrame()?

void ofGstUtils::goToNextFrame(){
    gst_element_send_event(gstPipeline,gst_event_new_step(GST_FORMAT_BUFFERS, 1, 1.0, TRUE, FALSE));
}

During that testing I also ran into similar problems when querying getPosition() as described here:

Gstreamer in paused mode - frame-by-frame

Hello. I ran into problems when using ofGstVideoPlayer in paused mode to do a frame-by-frame process with certain video-files. The video-track in those files is shorter than the file itself. In the attached file: testmovie.mov the 2 audio-tracks are a couple of frames longer than the video-track. testmovie.zip (60.8 KB) The problem occurs, when jumping after the last video-frame but before the end of the file. gstreamer waits for a sample which never appears. try this with attached videofil…

I know that dealing with videos one is always confronted with weird behaviour like sometimes videos have “no frames” and you can not use setFrame() or you only get a proper position after the first couple of frames, but maybe somebody has figured that out and could give me a hint regarding ofGstVideoPlayer and accurate positioning?
I am developing a tool which should work with whatever the user drags in so I want to provide a more or less universal solution

Thanks
Jakob

I attached a small FrameTestMovie (mov) I use for testing and it is one where the current nextFrame() and previousFrame() functions sometimes hang or skip a frame. FrameTestMovie_v001_trimmed.mov.zip (529.8 KB)

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Btw, I am using OF from the master branch with OSX and XCode 6.2

[inx]

Hello.

maybe this helps:
http://docs.gstreamer.com/display/GstSDK/Basic+tutorial+13%3A+Playback+speed

i did not try to use trickmodes myself. maybe i can manage to give it a try later.
might be we should use gst_event_new_seek instead of gst_element_seek…?

[fakob]

Thanks @inx.
I now see my limitations regarding GStreamer. I can not wrap my head around these different functions. Today I did not get it to work.
Have you achieved anything in this field?

I had found this article regarding frame accuracy related to ffmpeg, but the theory, I guess, is the same for any video library.
http://www.hackerfactor.com/blog/index.php?/archives/307-Picture-Go-Back.html