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slow video playback on PC

This topic contains 5 replies, has 2 voices, and was last updated by  Han 1 month ago.

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April 17, 2019 at 06:28 #12908

moolie_loo

Hi, I browsed previous topics and find that I have the same issue as those on Macs. Mine is a PC, the video format is MP4. The entire video is not in sync, the audio is faster than the visual. I tried changing preferences in Platoform/OS: Java DirectShow Framework (Java-Microsoft Media Foundation) to Java Media Framework (deprecated). Same issue. I know the video file is okay because when I play it in VCL, everything is in sync. When I play it on Windows Media Player, audio-visual is out of sync. Not sure if this info is important. Also, I have downloaded and used the latest ELAN 5.5 and issue persists. Any suggestions/fixes? Thanks.

April 17, 2019 at 16:45 #12909

Han

Just to be sure: do you only have a video file linked or a separate .wav file too? In case of the latter, which file is listed first in Edit-Linked Files?
(This to rule out that there are actually two players involved, instead of only one video player.)

-Han

April 17, 2019 at 20:22 #12910

moolie_loo

Hi Han, Yes, I think it is a video file linked to audio. I can’t find a separate .wav file.

Millie

April 18, 2019 at 10:08 #12911

Han

Hi Millie,
I’m sorry I missed a detail in your first message: it says that in Windows Media Player the video and audio are also out of sync? That is in fact important, because the MP4 player in ELAN is based on the same framework as WMP. VLC is not a good predictor in this case, because ELAN cannot use that player.
Maybe there is something in the encoding which prevents smooth playback. Would re-encoding be an option? Or maybe you can compare the encoding of your mp4 with the recommended settings in this encoding guide?

April 23, 2019 at 21:51 #12917

moolie_loo

Hi Han,

My colleague is looking into re-encoding the video. The process right now is that the video file is given to me, I personally don’t have a way of encoding it. In the meantime, I did compare the settings. Based on the pdf and the encoded video I have on file, the audio is not set at the recommended settings, eg.: 1) bitrate is 128 instead of 320kb/s; 2) sampling rate is 44.1 instead of 48kHz; 3) framerate is 15 frames/second… not sure how framerate compares to the GOP size which is recommended at 25.

Any other solutions I can try other than re-encoding video?

Thanks,

Millie

April 24, 2019 at 11:20 #12920

Han

The GOP value is independent of the frame rate. A frame rate of 15 fps is maybe unusual but I wouldn’t immediately expect it to be a problem. I wouldn’t expect the audio settings to be problematic either.

If you have the “FX” version installed (e.g. ELAN 5.5-FX for Windows), you can try the JavaFX based media player, via Edit Preferences and then the Platform/OS tab. You will have to reopen the file after changing this setting. If that player doesn’t play audio and video in sync, there is no alternative to re-encoding.

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