qml: keep paybackState values the same as qtmm
fix log crash. issue 310

QDebug* was deleted at ~QtAVDebug() after
QtAVDebug::debug() returns a
copy of QtAVDebug
add decoder dynamic properties used by UI
orientation range is [0, 360)
misc
qmL: add hasAudio hasVideo. wrong result if auto load
better error handling about format, resource and codec error.
orientation support for opengl based renderers
orientation support for qpainter based renderers
fix crash when a packet has null data
add subtitle in Video.qml for conveience
qml: set metaData.Size to file size

QtMultimedia use the value from meta data and only works on
windows. Not sure why
bgra format. issue 254
opengl display rgb with alpha correctly. qml can't
add a convenience class to extract frame at a given time
async frame extract support

TODO: why do event and slots not works?
qml: add Preview item
avoid preview seeking too frequent etc.
Merge branch 'preview'
preview: fix error decoding key frame after seek