What GStreamer pipelining is used in QtMultimedia for video playback?

[nickaein]

Hi,

I have some trouble in playing video inside my Qt application (discussion: https://forum.qt.io/topic/52676).

AFAIK, Qt 5.4.1 still use GStreamer 0.10 for playing videos. While I can successfully play videos using the following command:

gst-launch-0.10 playbin2 uri=file:///home/isaac/Desktop/sample_videos/480p.mp4

the video cannot be played by the example player program provided by Qt (located at Qt5.4.1/Examples/Qt-5.4/multimediawidgets/player).

The example program gives the following output with GST_DEBUG=2:

0:00:00.136079088  4038  0x82a5630 WARN                 qtdemux qtdemux_types.c:191:qtdemux_type_get: unknown QuickTime node type avc1
0:00:00.136191505  4038  0x82a5630 WARN                 qtdemux qtdemux_types.c:191:qtdemux_type_get: unknown QuickTime node type avcC
0:00:00.136228217  4038  0x82a5630 WARN                 qtdemux qtdemux_types.c:191:qtdemux_type_get: unknown QuickTime node type hmhd
0:00:00.136252646  4038  0x82a5630 WARN                 qtdemux qtdemux_types.c:191:qtdemux_type_get: unknown QuickTime node type name
0:00:00.136279442  4038  0x82a5630 WARN                 qtdemux qtdemux_types.c:191:qtdemux_type_get: unknown QuickTime node type hinf
0:00:00.136296196  4038  0x82a5630 WARN                 qtdemux qtdemux_types.c:191:qtdemux_type_get: unknown QuickTime node type hmhd
0:00:00.136310724  4038  0x82a5630 WARN                 qtdemux qtdemux_types.c:191:qtdemux_type_get: unknown QuickTime node type name
0:00:00.136331758  4038  0x82a5630 WARN                 qtdemux qtdemux_types.c:191:qtdemux_type_get: unknown QuickTime node type hinf
0:00:00.136357702  4038  0x82a5630 WARN                 qtdemux qtdemux_types.c:191:qtdemux_type_get: unknown QuickTime node type hinv
0:00:00.136496204  4038  0x82a5630 WARN                 qtdemux qtdemux.c:7044:qtdemux_parse_trak:<qtdemux0> unknown version 00000000
0:00:00.191816714  4038  0x856e030 WARN      playsinkconvertbin gstplaysinkconvertbin.c:481:gst_play_sink_convert_bin_cache_converter_caps:<GstPlaySinkAudioConvert@0xb1b4e028> No conversion elements
0:00:00.260514955  4038  0x856e030 WARN                  ffmpeg gstffmpegdec.c:2299:gst_ffmpegdec_frame:<ffdec_h2640> ffdec_h264: decoding error (len: -1, have_data: 0)
0:00:00.260632491  4038  0x82a5630 WARN                 qtdemux qtdemux.c:3891:gst_qtdemux_loop:<qtdemux0> error: streaming stopped, reason not-negotiated
Error: "GStreamer encountered a general stream error."

I wonder if the Qt is using some pipelining and plugins that are missing or not configured properly.

Here is list of installed packages (output of dpkg -l): http://pastebin.com/uKRXivFu