python gstreamer實現視訊快進/快退/迴圈播放功能
阿新 • • 發佈:2020-04-01
Gstreamer到底是個啥?
GStreamer 是一個 基於pipeline的多媒體框架,基於GObject,以C語言寫成。
應用GStreamer這個這個多媒體框架,你可以寫出任意一種流媒體的應用來如:meidaplayer、音視訊編輯器、VOIP、流媒體伺服器、音視訊編碼等等。
關於視訊快進/快退/迴圈播放的知識總結:
1.本地視訊時長獲取:
Gst.Pad.query_duration官方函式介紹:
def Gst.Pad.query_duration (self,format): #python wrapper for 'gst_pad_query_duration' Queries a pad for the total stream duration. Parameters: pad ( Gst.Pad ) –a Gst.Pad to invoke the duration query on. format ( Gst.Format ) –the Gst.Format requested Returns a tuple made of: ( gboolean ) –TRUE (not introspectable) if the query could be performed. duration ( gint64 ) –TRUE (not introspectable) if the query could be performed.
使用如下:
pipeline.query_duration(Gst.Format.TIME)[1]
其中pipeline為播放本地視訊的管道,query_duration()函式返回一個元組,元組的形式為[Ture,duration:******],******為以ns為單位的視訊時長。
2.視訊播放當前位置獲取:
Gst.Pad.query_position官方函式介紹:
def Gst.Pad.query_position (self,format): #python wrapper for 'gst_pad_query_position' Queries a pad for the stream position. Parameters: pad ( Gst.Pad ) –a Gst.Pad to invoke the position query on. format ( Gst.Format ) –the Gst.Format requested Returns a tuple made of: ( gboolean ) –TRUE (not introspectable) if the query could be performed. cur ( gint64 ) –TRUE (not introspectable) if the query could be performed.
使用方法與時長獲取函式query_duration()
相同。
3.播放跳轉函式:
Gst.Element.seek_simple官方函式介紹:
def Gst.Element.seek_simple (self,format,seek_flags,seek_pos): #python wrapper for 'gst_element_seek_simple' Parameters: element ( Gst.Element ) –a Gst.Element to seek on format ( Gst.Format ) –a Gst.Format to execute the seek in,such as Gst.Format.TIME seek_flags ( Gst.SeekFlags ) –seek options; playback applications will usually want to use GST_SEEK_FLAG_FLUSH | GST_SEEK_FLAG_KEY_UNIT here seek_pos ( gint64 ) –position to seek to (relative to the start); if you are doing a seek in Gst.Format.TIME this value is in nanoseconds - multiply with Gst.SECOND to convert seconds to nanoseconds or with Gst.MSECOND to convert milliseconds to nanoseconds. Returns ( gboolean ) : TRUE (not introspectable) if the seek operation succeeded. Flushing seeks will trigger a preroll,which will emit Gst.MessageType.ASYNC_DONE.
函式使用樣例:
pipeline.seek_simple(Gst.Format.TIME,Gst.SeekFlags.FLUSH,time)
其中time的單位為nanoseconds。
有視訊快進/快退/迴圈播放功能的小播放器.
import os,_thread,time import gi gi.require_version("Gst","1.0") gi.require_version('Gtk','3.0') from gi.repository import Gst,GObject,Gtk,Gdk class GTK_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,"WM destroy") vbox = Gtk.VBox() window.add(vbox) self.entry = Gtk.Entry() vbox.pack_start(self.entry,False,0) hbox = Gtk.HBox() vbox.add(hbox) buttonbox = Gtk.HButtonBox() hbox.pack_start(buttonbox,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) for ele in [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) def start_stop(self,w): if self.button.get_label() == "Start": filepath = self.entry.get_text().strip() if os.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") def play_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) while play_thread_id == self.play_thread_id: time.sleep(0.2) dur_int = self.player.query_duration(Gst.Format.TIME)[1] if dur_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) while play_thread_id == self.play_thread_id: pos_int = self.player.query_position(Gst.Format.TIME)[1] pos_str = self.convert_ns(pos_int) if play_thread_id == self.play_thread_id: Gdk.threads_enter() self.time_label.set_text(pos_str + " / " + dur_str) Gdk.threads_leave() time.sleep(1) def on_message(self,bus,message): t = message.type if t == Gst.MessageType.EOS: self.player.seek_simple(Gst.Format.TIME,0000000000) elif t == 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") def demuxer_callback(self,pad,dst): caps = Gst.Pad.get_current_caps(pad) structure_name = caps.to_string() if structure_name.startswith("video"): videorate_pad = dst.get_static_pad("sink") pad.link(videorate_pad) def rewind_callback(self,w): rc,pos_int = self.player.query_position(Gst.Format.TIME) seek_ns = pos_int - 10 * 1000000000 if seek_ns < 0: seek_ns = 0 print ('Backward: %d ns -> %d ns' % (pos_int,seek_ns)) self.player.seek_simple(Gst.Format.TIME,seek_ns) def forward_callback(self,pos_int = self.player.query_position(Gst.Format.TIME) seek_ns = pos_int + 10 * 1000000000 print ('Forward: %d ns -> %d ns' % (pos_int,seek_ns) def convert_ns(self,t): s,ns = divmod(t,1000000000) m,s = divmod(s,60) if m < 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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