[digikam] [Bug 374355] New: Video preview lags in the beginning

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https://bugs.kde.org/show_bug.cgi?id=374355

            Bug ID: 374355
           Summary: Video preview lags in the beginning
           Product: digikam
           Version: 5.4.0
          Platform: Other
                OS: MS Windows
            Status: UNCONFIRMED
          Severity: normal
          Priority: NOR
         Component: AlbumsView
          Assignee: [hidden email]
          Reporter: [hidden email]
  Target Milestone: ---

Hello, I am really enjoying that digikam can now play video files but mine
usually lags for 2-3 seconds in the beginning of each video. Every mp4 file
starts in slow motion for me.

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--- Comment #1 from [hidden email] ---
Can you download QtAV for windows and look if problem is the same.

QtAV framework is used inside digiKam to play video.

http://www.qtav.org/

Gilles Caulier

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Bill Goodman <[hidden email]> changed:

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--- Comment #2 from Bill Goodman <[hidden email]> ---
I see the same 2-3 second lag at the beginning of videos on Win7 but I do not
see it on Win10. Both using digiKam 5.4.0

Also, in Win7, the video repeatedly plays the last 0.25 second of audio when it
hits the end of the video. No way to stop the sound repeating. The same
repeating sound happens if the video is paused in the middle.

In Win10, the current time indicator at the bottom of the preview window keeps
counting when the video reaches the end. This does not happen in Win7.

I will try to install the QtAV framework and see if it has the same behavior.

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--- Comment #3 from Bill Goodman <[hidden email]> ---
I installed QtAV1.11.0-VS2013x86.exe on Win7 and do not see the initial lag
problem using QtAV.Player.

I also do not see the issue with audio repeating endlessly when the video is
stopped in Win7.

No testing done on Win10.

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--- Comment #4 from [hidden email] ---
I think the big difference between digiKam fopr Window and QtAV player is the
way to compile source code. digiKam use MXE crosss compiler, QtAV M$ Visual C++
(i think).

So the optimizations can be very different, about DirectX for ex.

Note : under MacOS and Linux, DK do not have this kind of latency problem.

Gilles Caulier

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--- Comment #5 from wildcowboy <[hidden email]> ---
I just installed QtAV on my Windows 10 but it did not change much. I am okay
with the latency issue but the fact that QtAV does not see the rotation flag is
annoying. I guess I will be pressing F4 instead of double clicking on mp4 files
for now.

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--- Comment #6 from [hidden email] ---
Note : about rotation, Video digiKam preview permit to rotate media with left
mouse button over canvas.

Gilles Caulier

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--- Comment #7 from wildcowboy <[hidden email]> ---
I get a slideshow instead of a video preview on digiKam 5.4.0 on linux Mint
18.1 KDE. There is no sound either.

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--- Comment #8 from wildcowboy <[hidden email]> ---
Looks like the output depends on the codec. Videos straight out of phone just
lag in the beginning, videos compressed using ffmpeg are slideshows (very very
slow)

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--- Comment #9 from wildcowboy <[hidden email]> ---
(In reply to wildcowboy from comment #8)
> Looks like the output depends on the codec. Videos straight out of phone
> just lag in the beginning, videos compressed using ffmpeg are slideshows
> (very very slow)

Replying to my own comment.
Now it looks like I have no lags with videos created by ffmpeg but there is a
lag with videos created by phone/camera

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--- Comment #10 from [hidden email] ---
I updated all DK 5.5.0 Bundle as pre-version release using last implementation
from QtAV. Files are here :

https://drive.google.com/drive/folders/0BzeiVr-byqt5Y0tIRWVWelRJenM

Can you test to see if problem still there ? Thanks in advance...

Gilles Caulier

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--- Comment #11 from [hidden email] ---
The lag can be also due to non OpenGL video widget used in digiKam. I used a
simple widget, not based on OpenGL to not depend on it with video support.

This is of course not optimum.

The question is : the QtAV open GL widget will have low performnce if OpenGL is
not available on client computer ? AppImage bundle do not know the target
computer feature. OpenGL can be not available. If it's the case, the whish is
to see QtAv video widget switching in decrease mode, typically in simple widget
rendering.

So QtAv openGL widget is adaptive with hardware ?

Gilles Caulier

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--- Comment #12 from wildcowboy <[hidden email]> ---
(In reply to caulier.gilles from comment #10)
> I updated all DK 5.5.0 Bundle as pre-version release using last
> implementation from QtAV. Files are here :
>
> https://drive.google.com/drive/folders/0BzeiVr-byqt5Y0tIRWVWelRJenM
>
> Can you test to see if problem still there ? Thanks in advance...
>
> Gilles Caulier

Nothing changed on Linux Mint.
Here is a screen cast:
https://youtu.be/nqG9KZt8f9k

This record actually looks worse than it is but that 1-2-3 latency in the
beginning of the video looks realistic.

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--- Comment #13 from Bill Goodman <[hidden email]> ---
The lag seems to be gone on my Windows 7 system. There is a 1-2 second delay
the first time I play a video, but then the video plays correctly from the
beginning. I think that previously it was advancing through the movie during
that time without correctly showing video. And it seems that after the first
play, on subsequent plays the video shows with no initial delay at all, like
something is being cached somewhere. This seems to be true even if I exit
digiKam and restart it.

More good news: the extremely annoying repeat of audio at the end of playing a
movie also seems to be fixed.

Bad news: In preview, switching from one video to another while the first video
is playing causes the media player to report an error and no video is shown.

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--- Comment #14 from [hidden email] ---
I posted an UPSTREAM report to QtAV team :

https://github.com/wang-bin/QtAV/issues/835

Gilles Caulier

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--- Comment #15 from [hidden email] ---
We need debug statements printed on the console when a video is played in
digiKam. For Linux, just run digiKam from a terminal.

For Windows, you need to install debugview program and run digiKam. debugview
will capture all debug statements from digiKam. See this page for details :

https://www.digikam.org/contrib

Gilles Caulier

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--- Comment #16 from Bill Goodman <[hidden email]> ---
Created attachment 104518
  --> https://bugs.kde.org/attachment.cgi?id=104518&action=edit
Screenshot of video switch failure

Screenshot of DebugView log during video switch failure.

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--- Comment #17 from [hidden email] ---
There is nothing about video player.

Can you share the full debug trace from the beginning of digiKam ?

Gilles Caulier

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--- Comment #18 from Bill Goodman <[hidden email]> ---
Created attachment 104519
  --> https://bugs.kde.org/attachment.cgi?id=104519&action=edit
DebugView log of video switch failure

1: Launch digiKam
276: Open preview of first video
283: Switch to second video

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