[gst-devel] problem when getting the data of a frame

[Vincent Torri]

Hello,

I have this simple pipeline (not a thread)

+---------------------------------------------------+
|                                                   |
|  pipeline                                         |
|                                                   |
|  +---------+  +-----------+  +------------------+ |
|  |         |  |           |  |                  | |
|  | filesrc +--+ decodebin +--+ (video) fakesink | |
|  |         |  |           |  |                  | |
|  +---------+  +-----------+  +------------------+ |
|                                                   |
+---------------------------------------------------+

my aim is to get the frame #n, i don't care about the colorspace. I use
gstreamer 0.8 (with gst-plugins and gst-ffmpeg)

I am able to get the informations (resolution, length, colorspace, etc..)
of the video.

so, on the sink, i've attached a callback on the "handoff" signal.

a) I seek to frame #n (with DEFAULT type, it works as it returns true)
b) I set the pipeline to PLAY state
c) I iterate ( while (iterate) { })
d) the calback is executed
   1) I set the state of the pipeline to PAUSED to stop the iteration
   2) I store the data of the buffer
e) I draw the Y plane in a .ppm file

but, in the ppm file, i only get values between 29 and 32. I've tried
lots of frames of the video, in particular frames with hight luma. I only
get a grey rectangle.

the colorspace of the video is I420, the resolution is 704x400
The size of the buffer is 422400 which is equal to 704*400 + 352*200 +
352*200. So I think that the buffer is filled with data (maybe not the
good ones...)

Does someone see if there is a problem in the pipeline (I think that it's
the only place where the error can be located)

thank you

Vincent Torri