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  1. #1
    Nokia Developer Expert
    Join Date
    Jan 2006

    QMediaPlayer video playback issue

    I'm currently investigating an odd problem whereby an application that uses QMediaPlayer to playback video files is experiencing intermittent playback problems.

    When the problem occurs, no video frames are rendered, but the video's audio track is played correctly.

    At no time is an error reported and all player state and media status changes are valid and sensible, suggesting the media is opened, buffered and played correctly.

    I've checked system RAM, application heap and used GOOM to verify that no low memory events are being generated by the GPU. So this doesn't seem to be an OOM or GOOM issue.

    I'm trying to build a debug version of Qt Mobility (or QtMultimediaKit) to allow me to investigate what is happening within QMediaPlayer, but so far I am unable to build the code. (If I build QtMobility, there are missing directories and headers, if I just build QtMultimediaKit there are problems with symbols missing from the Elf file!)

    Currently building with Qt SDK 1.1.1 / Qt 4.7.3 for Symbian^3 / Qt Mobility 1.1.3.

    The problem is completely intermittent and only affects some individual C7 and N8 handsets (not whole phone models).

    Has anyone else experienced this sort of difficulty with QMediaPlayer? Any hints as to what I should look at next?

    Thanks in advance!

  2. #2
    Nokia Developer Expert
    Join Date
    Jan 2006

    Re: QMediaPlayer video playback issue

    Further investigation seems to suggest that setting Media and VideoOutput on QMediaPlayer and then calling play, as shown in the documentation and all sample code is not sufficient.
    Having prepared the QMediaPlayer instance, I now defer calling play until I've received a signal to tell me the media has been loaded. Calling play prior to confirmation the media has loaded seems quite unreliable.

    However, even that isn't sufficient. I still have a problem whereby the first attempted play of a video clip in my application still only plays the audio track. Subsequent plays of the same or other video clips from that point on work, playing both video and audio.

    My assumption is that there is some plugin that needs to be loaded, which isn't being loaded before my application calls play, but that is available the next time I try to play a video.
    Is that correct? If so, how do I guarantee that my QMediaPlayer object is fully ready to play my video clip? How can I force all necessary components / plugins to be loaded?

    Thanks in advance!

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