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willprice / python-omxplayer-wrapper

:tv: Control OMXPlayer, the Raspberry Pi media player, from Python
http://python-omxplayer-wrapper.readthedocs.io
GNU Lesser General Public License v3.0
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Small Issue with set position #114

Closed therysin closed 6 years ago

therysin commented 6 years ago

Hey Will, thanks for all the work on this library. I managed to get this issue on both a raspi 2 model b and 3 model b.

Sometimes when I use the player.set_position() command it's a few seconds off.

To reproduce the problem I did a simple video playback with a video that had timestamps onscreen, and using the set position command to go to 20 seconds, 25, 45 and repeat. I did a short video in for you with the issue. https://youtu.be/rNVN8iJ6Hts

I'm really new with the raspberry pi, so I couldn't really follow the template fully. I'm on the latest version of the wrapper (installed from pip 2 days ago) and I only installed raspbian about 2 weeks ago from the official site.

Thanks for everything, I'm using your wrapper to synchronize video playback for a school project. Thanks again.

jehutting commented 6 years ago

Is it possible to post the video you are playing?

therysin commented 6 years ago

Thanks for the reply, here is the video: http://pocketvj.com/video/small_testfile.mp4

jehutting commented 6 years ago

I played the video with (the real) omxplayer and used dbuscontrol.sh to do the setpositions. I can see the few seconds off too.

AFAIK when omxplayer executes a setposition, it seeks to the nearest keyframe. In your case setposition of 20 secs results in a keyframe around 18 secs, 25 secs to keyframe 24 secs, and 45 secs to keyframe 45 secs. That's the time off time you get.

I think it depends on how the video is made. E.g. take https://www.edius.de/test/foo.mp4, a h264/1080p50 video of 30 seconds and look how almost accurate the setpositions are.

therysin commented 6 years ago

Thanks for the reply jehutting. I think I understand now. Can you offer any advice on setting the position accurately for any(sub 40 fps) video though? I was looking at the seek function but that seems to look for a key frame around 5 seconds too. Thanks again.

jehutting commented 6 years ago

Unfortunately I have no advice on how to improve the seeking/positioning. It has been a while ago I looked at it but ffmpeg -on which omxplayer leans on- is just one step too far for me :-(

therysin commented 6 years ago

That's okay. Thanks for the help and replies 😊. I managed to do synchronization by skipping a little ahead on one player then pausing for the deviation and that works very well. Now the next step for me would be loading more than one video from a directory. Thanks again Jehutting!