python gstreamer实现视频快进/快退/循环播放功能
Gstreamer到底是个啥？
GStreamer是一个基于pipeline的多媒体框架，基于GObject，以C语言写成。
应用GStreamer这个这个多媒体框架，你可以写出任意一种流媒体的应用来如：meidaplayer、音视频编辑器、VOIP、流媒体服务器、音视频编码等等。
关于视频快进/快退/循环播放的知识总结:
1.本地视频时长获取:
Gst.Pad.query_duration官方函数介绍:
defGst.Pad.query_duration(self,format): #pythonwrapperfor'gst_pad_query_duration' Queriesapadforthetotalstreamduration. Parameters: pad(Gst.Pad)–aGst.Padtoinvokethedurationqueryon. format(Gst.Format)–theGst.Formatrequested Returnsatuplemadeof: (gboolean)–TRUE(notintrospectable)ifthequerycouldbeperformed. duration(gint64)–TRUE(notintrospectable)ifthequerycouldbeperformed.
使用如下:
pipeline.query_duration(Gst.Format.TIME)[1]
其中pipeline为播放本地视频的管道,query_duration()函数返回一个元组,元组的形式为[Ture,duration:******]，******为以ns为单位的视频时长。
2.视频播放当前位置获取：
Gst.Pad.query_position官方函数介绍：
defGst.Pad.query_position(self,format): #pythonwrapperfor'gst_pad_query_position' Queriesapadforthestreamposition. Parameters: pad(Gst.Pad)–aGst.Padtoinvokethepositionqueryon. format(Gst.Format)–theGst.Formatrequested Returnsatuplemadeof: (gboolean)–TRUE(notintrospectable)ifthequerycouldbeperformed. cur(gint64)–TRUE(notintrospectable)ifthequerycouldbeperformed.
使用方法与时长获取函数query_duration()相同。
3.播放跳转函数：
Gst.Element.seek_simple官方函数介绍：
defGst.Element.seek_simple(self,format,seek_flags,seek_pos): #pythonwrapperfor'gst_element_seek_simple' Parameters: element(Gst.Element)–aGst.Elementtoseekon format(Gst.Format)–aGst.Formattoexecutetheseekin,suchasGst.Format.TIME seek_flags(Gst.SeekFlags)–seekoptions;playbackapplicationswillusuallywanttouseGST_SEEK_FLAG_FLUSH|GST_SEEK_FLAG_KEY_UNIThere seek_pos(gint64)–positiontoseekto(relativetothestart);ifyouaredoingaseekinGst.Format.TIMEthisvalueisinnanoseconds-multiplywithGst.SECONDtoconvertsecondstonanosecondsorwithGst.MSECONDtoconvertmillisecondstonanoseconds. Returns(gboolean): TRUE(notintrospectable)iftheseekoperationsucceeded.Flushingseekswilltriggerapreroll,whichwillemitGst.MessageType.ASYNC_DONE.
函数使用样例：
pipeline.seek_simple(Gst.Format.TIME,Gst.SeekFlags.FLUSH,time)
其中time的单位为nanoseconds。
有视频快进/快退/循环播放功能的小播放器.
importos,_thread,time
importgi
gi.require_version("Gst","1.0")
gi.require_version('Gtk','3.0')
fromgi.repositoryimportGst,GObject,Gtk,Gdk
classGTK_Main:
def__init__(self):
window=Gtk.Window(Gtk.WindowType.TOPLEVEL)
window.set_title("Vorbis-Player")
window.set_default_size(500,-1)
window.connect("destroy",Gtk.main_quit,"WMdestroy")
vbox=Gtk.VBox()
window.add(vbox)
self.entry=Gtk.Entry()
vbox.pack_start(self.entry,False,False,0)
hbox=Gtk.HBox()
vbox.add(hbox)
buttonbox=Gtk.HButtonBox()
hbox.pack_start(buttonbox,False,False,0)
rewind_button=Gtk.Button("Rewind")
rewind_button.connect("clicked",self.rewind_callback)
buttonbox.add(rewind_button)
self.button=Gtk.Button("Start")
self.button.connect("clicked",self.start_stop)
buttonbox.add(self.button)
forward_button=Gtk.Button("Forward")
forward_button.connect("clicked",self.forward_callback)
buttonbox.add(forward_button)
self.time_label=Gtk.Label()
self.time_label.set_text("00:00/00:00")
hbox.add(self.time_label)
window.show_all()
self.player=Gst.Pipeline.new("player")
source=Gst.ElementFactory.make("filesrc","file-source")
demuxer=Gst.ElementFactory.make("decodebin","demuxer")
videoconv=Gst.ElementFactory.make("videoconvert","converter")
videosink=Gst.ElementFactory.make("xvimagesink","video-output")
demuxer.connect("pad-added",self.demuxer_callback,videoconv)
forelein[source,demuxer,videoconv,videosink]:
self.player.add(ele)
source.link(demuxer)
videoconv.link(videosink)
bus=self.player.get_bus()
bus.add_signal_watch()
bus.connect("message",self.on_message)
defstart_stop(self,w):
ifself.button.get_label()=="Start":
filepath=self.entry.get_text().strip()
ifos.path.isfile(filepath):
filepath=os.path.realpath(filepath)
self.button.set_label("Stop")
self.player.get_by_name("file-source").set_property("location",filepath)
self.player.set_state(Gst.State.PLAYING)
self.play_thread_id=_thread.start_new_thread(self.play_thread,())
else:
self.play_thread_id=None
self.player.set_state(Gst.State.NULL)
self.button.set_label("Start")
self.time_label.set_text("00:00/00:00")
defplay_thread(self):
play_thread_id=self.play_thread_id
Gdk.threads_enter()
self.time_label.set_text("00:00/00:00")
Gdk.threads_leave()
print(play_thread_id)
print(self.play_thread_id)
whileplay_thread_id==self.play_thread_id:
time.sleep(0.2)
dur_int=self.player.query_duration(Gst.Format.TIME)[1]
ifdur_int==-1:
continue
dur_str=self.convert_ns(dur_int)
Gdk.threads_enter()
self.time_label.set_text("00:00/"+dur_str)
Gdk.threads_leave()
break
time.sleep(0.2)
whileplay_thread_id==self.play_thread_id:
pos_int=self.player.query_position(Gst.Format.TIME)[1]
pos_str=self.convert_ns(pos_int)
ifplay_thread_id==self.play_thread_id:
Gdk.threads_enter()
self.time_label.set_text(pos_str+"/"+dur_str)
Gdk.threads_leave()
time.sleep(1)
defon_message(self,bus,message):
t=message.type
ift==Gst.MessageType.EOS:
self.player.seek_simple(Gst.Format.TIME,Gst.SeekFlags.FLUSH,0000000000)
elift==Gst.MessageType.ERROR:
err,debug=message.parse_error()
print("Error:%s"%err,debug)
self.play_thread_id=None
self.player.set_state(Gst.State.NULL)
self.button.set_label("Start")
self.time_label.set_text("00:00/00:00")
defdemuxer_callback(self,demuxer,pad,dst):
caps=Gst.Pad.get_current_caps(pad)
structure_name=caps.to_string()
ifstructure_name.startswith("video"):
videorate_pad=dst.get_static_pad("sink")
pad.link(videorate_pad)
defrewind_callback(self,w):
rc,pos_int=self.player.query_position(Gst.Format.TIME)
seek_ns=pos_int-10*1000000000
ifseek_ns<0:
seek_ns=0
print('Backward:%dns->%dns'%(pos_int,seek_ns))
self.player.seek_simple(Gst.Format.TIME,Gst.SeekFlags.FLUSH,seek_ns)
defforward_callback(self,w):
rc,pos_int=self.player.query_position(Gst.Format.TIME)
seek_ns=pos_int+10*1000000000
print('Forward:%dns->%dns'%(pos_int,seek_ns))
self.player.seek_simple(Gst.Format.TIME,Gst.SeekFlags.FLUSH,seek_ns)
defconvert_ns(self,t):
s,ns=divmod(t,1000000000)
m,s=divmod(s,60)
ifm<60:
return"%02i:%02i"%(m,s)
else:
h,m=divmod(m,60)
return"%i:%02i:%02i"%(h,m,s)
GObject.threads_init()
Gst.init(None)
GTK_Main()
Gtk.main()
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