[Qt-interest] jerkiness in video on using phonon on windows

[Jason H]

Some questions/tests

Is the QIODevice sequential? (socket?)
With 2-3 second jerkiness, it sounds like the codec (or i/o) is going back to the last I frame after exhausting P frames. Can you transcode it to be all I frames?
I think it may  be a problem with a partial read (in that you don't have a complete I/P frame) and that the Codec is resuming from the last I-frame. Meanign to me, it could be a buffering problem. Which then begs the question, if the media in a QBuffer? Does it work when it is?





----- Original Message ----
From: Kunal Lagwankar <kunal at novix.in>
To: qt-interest at trolltech.com
Sent: Fri, November 20, 2009 9:55:25 AM
Subject: [Qt-interest] 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

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