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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