[Interest] [qt-Android] MediaPlayer freeze UI when playing a remote video

[Liang Jian]

    After some debugging I finally found the root cause of the freeze:
     When we set source to the Audio or MediaPlayer element,
QAndroidMediaPlayerControl::setMedia() will be called to set the media
source to the underlying android MediaPlayer, then mediaChanged signal will
be emitted, which lead to --->
QAndroidMetaDataReaderControl::onMediaChanged() --->
QAndroidMetaDataReaderControl::updateData() --->
AndroidMediaMetadataRetriever::extractMetadata() --->
android.media.MediaMetadataRetriever.extractMetadata() get called which
will retrieve the meta data of the media file.
     android.media.MediaMetadataRetriever.extractMetadata() is apparently a
synchronous API, when network is bad, it will wait until it fetched the
meta-data (or failed) and please note that this is called under Qt's UI
thread and it will freeze the UI for a potentially very long time.

On Wed, Nov 18, 2015 at 9:39 AM, Liang Jian <jianliang79 at gmail.com> wrote:

>     When network is not good, MediaPlayer will freeze UI when playing a
> remote video under android. After I set a video url to MediaPlayer, it
> seems that it will fetch meta-data of the video first, and if the network
> is not good, it will freeze UI for a very long time.
>     A very similar problem which is related to Audio quick element has
> been reported in https://bugreports.qt.io/browse/QTBUG-46491.
>     This has become a very common issue for our app, since once our app
> published a video to the internet, we will use CDN to speed up video
> playback
> from network, suppose at the first time a person in a area (I mean a CDN
> node)
> watch a video, CDN will fetch the whole content of the video from the
> original
> website to the current CDN node, this usually takes 10-20s (or even more),
> that to say our android app will freeze the UI for 10-20s or even more
> time!
> A bug report has been submitted long time ago:
>     This issue only happen under android, it will not happen under Windows
> or iOS.
>     Any suggestion to workaround this issue? thanks.
>
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