this is really rather the crux of my software
from what i can tell about Qt6, the removed functionality will make it
impossible to have my software work?
please tell me how i'm wrong?
thanks
> On Jul 7, 2021, at 6:59 PM, David M. Cotter <d...@kjams.com> wrote:
>
> in qt5 i could call mediaPlayerP->setVideoOutput(const QList<QVideoSink *>
> &sinks)
> this is no longer available, unless enough of us complain, i guess. well here
> i am.
>
> my media player app can output to 3 different scenes in 3 different windows.
> with qt6 it can no longer do that.
>
> i thought i might be able to derive QVideoSink, and just make a
> "CMultiplexVideoSink" out of it, which is an accepted trick to get a
> QCameraDevice to be capable of sending its output to multiple destinations,
> but you can't derive from QVideoSink because there are no virtual methods :(
>
> so that method won't work for media player (also won't work for camera, see
> my other post on that.
>
> how am i supposed to do this now?
>
> next question:
> if one has a requirement to have a video's dimensions and duration BEFORE
> playing the video (eg: to create a buffer, resize a window, or to set up a
> timeline GUI that shows the proper end time), an acceptable method in the
> past was to "preroll" the video by starting to play it with no visible or
> audible interface, start it (secretly) playing, spin an event loop waiting
> for the messages "QAbstractVideoSurface::surfaceFormatChanged" and
> "QMediaPlayer::durationChanged", and when received, store the data, tear it
> all down, and THEN present the interface and start playing the video.
>
> but... there is no surfaceFormatChanged signal in QVideoSink.
>
> does metadata actually work now to the point where i can grab the dimensions
> and duration without prerolling the movie?
>
> also, and this seems to be something rather important, there used to be a "
> QMediaPlayer::error" signal that one could listen for. it's gone. how do we
> know when an error occurs now?
>
> similar to above, when constructing a QGraphicsScene with a
> QVideoGraphicsItem that was mapped from a QImage (not from a video), then, at
> the first presentation, one could ask the surface if it were active, and if
> not, one would have to call surfaceP->start() (do we need to do this any
> more?) then one would spin a bit on an event loop waiting for
> handleNativeSizeChanged, so the graphicsItem could know the proper
> dimensions, so it would not first present with wrong dimensions..
>
> like this:
> void CG_Overlay::present(
> QtAbstractVideoSurface *surfaceP,
> const QVideoFrame& frame)
> {
> #if _QT6_
> {
> QSize vidSize(surfaceP->videoSize());
>
> CF_ASSERT(!vidSize.isEmpty());
> }
> #else
> if (!surfaceP->isActive()) {
> bool
> startedB(surfaceP->start(surfaceFormat(frame)));
> CTimerSince timer;
>
> CF_ASSERT(startedB);
>
> // wait for dimensions to get got
> // so the first presentation has
> // correct aspect ratio
> setHasDimensions(false);
>
> while (!hasDimensions() && !QtFireTimersUntilExpire(timer)) {}
> }
> #endif
>
> // if you can't get the CDG image to appear for
> // presentation, see comment in CPixels::hqx_blit()
> #if _QT6_
> surfaceP->newVideoFrame(frame);
> #else
> surfaceP->present(frame);
> #endif
> }
>
> in the above, QtAbstractVideoSurface is a QVideoSink., and the first assert
> fires (vidSize is in fact empty)
>
> in qt6 there isn't a way to do this :(
>
> what am i missing?
>
> -dave
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