jerkiness in video on using phonon on windows

Hi,


We are subclassing QIODevice to pass audio-video data to a custom parser (a Directshow filter implementation) using Phonon. Phonon creates a graph that includes the custom parser and corresponding audio-video decoders and rendering filters. The custom parser internally separates audio and video, which is then decoded and rendered.
When this sequence is played, jerkiness is observed periodically (spaced every 2-3 seconds). By video jerkiness, I mean that previous frame is again rendered causing a break in continuous viewing. It is important to note that there is no break in audio.

When the same file with the custom format is drag-n-dropped in to Graphedit, it automatically creates a pipeline and renders audio-video data satisfactorily (meaning no jerkiness and in audio-video synchronization). From this, we have concluded that the directshow filters by themselves do not have any bug and perform correctly.

We are unable to figure out why this behaviour is observed on using phonon in windows. Any help/suggestions in this matter will be appreciated.

Thanks.

Kunal