decodebin3: Race with caps changing in stream

Submitted by Arun Raghavan @arun

Link to original bug (#607471)

Description

While playing the following file, I do not see the video, only a still image:

http://samples.mplayerhq.hu/archive/container/mov/mov+svq3+aac++animatrix_2_program_640-sample.mov

gst-launch then quits with the following error:

$ gst-launch playbin2 uri=file:///$PWD/mov+svq3+aac++animatrix_2_program_640-sample.mov
Setting pipeline to PAUSED ...
Pipeline is PREROLLING ...
Pipeline is PREROLLED ...
Setting pipeline to PLAYING ...
New clock: GstPulseSinkClock
ERROR: from element /GstPlayBin2:playbin20/GstURIDecodeBin:uridecodebin0/GstDecodeBin2:decodebin20/GstJpegDec:jpegdec0: Failed to decode JPEG image
Additional debug info:
gstjpegdec.c(1261): gst_jpeg_dec_chain (): /GstPlayBin2:playbin20/GstURIDecodeBin:uridecodebin0/GstDecodeBin2:decodebin20/GstJpegDec:jpegdec0:
Error #70: Unsupported marker type 0x%02x
Execution ended after 3505994408 ns.
Setting pipeline to PAUSED ...
Setting pipeline to READY ...
Setting pipeline to NULL ...
Freeing pipeline ...

---

FWIW, I noticed that the stream topology that gets posted looks like this:

CONTAINER: video/quicktime
AUDIO: audio/mpeg, mpegversion=(int)4, framed=(boolean)true, codec_data=(buffer)1210, rate=(int)44100, channels=(int)2
AUDIO: audio/x-raw-int, endianness=(int)1234, signed=(boolean)true, width=(int)16, depth=(int)16, rate=(int)44100, channels=(int)2
UNKNOWN: image/jpeg, width=(int)640, height=(int)272, framerate=(fraction)15/1
VIDEO: video/x-raw-yuv, format=(fourcc)I420, width=(int)640, height=(int)272, framerate=(fraction)15/1