QMediaPlayer: setPosition jumps to key frames



  • I want to jump to arbitrary position in a video (while the video don't play). When using a compressed format (H264), setPosition() jumps to the closest key frame (it seems to). How can I do to access images between key frames?
    Here is the code
    @
    fMediaPlayer.play ();
    fMediaPlayer.setPosition( pos );
    fMediaPlayer.pause ();
    @

    fMediaPlayer is a QMediaPlayer. Note that it works when the video is compressed as jpeg.
    Any idea of what's wrong ?

    Dominique



  • I think it may depend on OS multimedia backend.

    But in H.264 you have to start to decode from key-frame.
    Because all other frames are just the differences between two key-frames, so nobody will be able to show it.

    If video is decoded as jpeg then all frames are full jpeg images.

    I guess you have to have running decoder to jump between each frame in H.264.



  • bq. I guess you have to have running decoder to jump between each frame in H.264.

    That's what I think too. Thus the question is how can I force decoding without playing.



  • If a decoder is running but the frames are not shown then you need to store or to drop the frames.

    "Here":http://qt-project.org/doc/qt-5/videooverview.html#working-with-low-level-video-frames is a short info about how to work with the frames.

    What is your use case, why do you need to setPosition() to all frames in a stream?



  • Thanks for the link. I'll give it a try.
    I'm using video in a musical context. Arbitrary jump to any time location must be supported (while playing or not) and with accurate time synchronization with other medias. This is why I need setPosition().


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