Phonon: Move disk access off the main thread



  • Hi,

    I am writing a "digital signage" application that needs to run on Windows, Mac OS X and (maybe/later) Linux. The app displays various kinds of media in multiple zones on the screen. For example; A slideshow of images on the left side, videos on the right side and a text ticker on the bottom. The tricky part is, as one would expect ;), the ticker. I'm using QPropertyAnimation to animate the "pos" of a QLabel.

    This works fine until a new file gets loaded for the slide show or the video. AFAIK the QPropertyAnimation uses a QTimeLine or some other kind of timer that fires every 40 ms to achieve a decent framerate. Accessing the disk usually takes longer than 40 ms, which results in the ticker pausing.

    Since I can't put the ticker on another thread, I need to move the disk access off the main thread. To easily try different approaches, I've created a small test app that only contains the relevant parts. The code is available here: "http://bitbucket.org/haikoschol/tickertest":http://bitbucket.org/haikoschol/tickertest

    For images I've found a solution that works without taking up too much memory (as did simply caching all images); "http://bitbucket.org/haikoschol/tickertest/src/eb800a2c7474/imagecache.cpp":http://bitbucket.org/haikoschol/tickertest/src/eb800a2c7474/imagecache.cpp

    I'm sure this could be improved, but it works. Since videos can get really large, I can't do the same thing there. So I tried to at least create a MediaSource object in advance, in the hope of saving the disk seek time. This doesn't seem to make a difference, though. I considered subclassing QIODevice to buffer parts of the file on a thread, but then I found this in the docs: "Warning: On Windows, we only support QIODevices containing the avi, mp3, or mpg formats."

    Any ideas what else I could try?

    edit: fixed links



  • Would QtMultimedia in 4.7 be any good? From my experience, Phonon is more or less now only suitable for dummy playback, and nothing else.



  • I haven't looked into 4.7, yet. Will do that now. Thanks for the hint.


Log in to reply
 

Looks like your connection to Qt Forum was lost, please wait while we try to reconnect.