Faster Video Seeking

[Tim Müller]

On Wed, 2014-03-26 at 20:22 +0900, Lasse Laursen wrote:

Hi Lasse,

> I am a little surprised that I've not been able to find any discussions 
> or thoughts on improving the seek-times of Gstreamer. Perhaps it's 
> because I'm in kind of a unique usage scenario? I'm using video 
> scrubbing as a means to test an interaction method, so I've created a 
> simple app where the user can drag a slider widget to scrub through a video.
> 
> I've built the playback pipeline using 'uridecodebin' and use it to 
> create a raw frame I can display on a texture in my app. I use the 
> 'gst_element_seek_simple' function call to seek through frames in a 
> video. I run it in a separate thread and ignore any additional calls 
> until the original call has returned. The video is in webm format with a 
> resolution of 1280x720. Currently, it's very juttery. Seeking to a new 
> frame takes quite a while. Much longer than I need for properly testing 
> my interaction method. I'm assuming the slow seek times is due to 
> gStreamer accessing the video as stored on the HD? So slow HD access times.
> 
> Potential Solutions:
> 
> 1) The easiest solution is undoubtedly to reduce the resolution. Not 
> great, but a last resort, if needed.
> 
> 2) Load the entire video file into memory. Is this even possible via 
> gStreamer? The file is only about 1 minute long and fills 15 megs 
> encoded as a webm file. This would be my preferable solution - but 
> again, I worry if it's possible? Could only find 'uri' paths that point 
> to files or online locations.
> 
> 3) Optimizing the gStreamer pipeline while still keeping the rest of my 
> code intact. Is using uridecodebin a bad thing? Is there a better/faster 
> way for me to display single frames in my app?
> 
> I hope someone can hint me towards the most viable approach.

It would be useful to see both your test file and your code. Are you
doing a KEY_UNIT seek? Are you doing an ACCURATE seek? etc. How slow or
fast seeking is depends a lot on the file in question, whether there's
an index, what the keyframe spacing is, if you do a key unit seek, etc.
Have you tried seeking in Totem (just keep the button pressed and move
the slider handle)?
 
 Cheers
  -Tim

-- 
Tim Müller, Centricular Ltd - http://www.centricular.com