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:
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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 requestedReturns 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：
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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 requestedReturns 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：
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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 onformat ( Gst.Format ) –a Gst.Format to execute the seek in, such as Gst.Format.TIMEseek_flags ( Gst.SeekFlags ) –seek options; playback applications will usually want to use GST_SEEK_FLAG_FLUSH | GST_SEEK_FLAG_KEY_UNIT hereseek_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.
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import os, _thread, timeimport gigi.require_version("Gst", "1.0")gi.require_version('Gtk', '3.0')from gi.repository import Gst, GObject, Gtk, Gdkclass 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, 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) 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, Gst.SeekFlags.FLUSH, 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, demuxer, 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, Gst.SeekFlags.FLUSH, seek_ns) def forward_callback(self, w): rc, 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)) self.player.seek_simple(Gst.Format.TIME, Gst.SeekFlags.FLUSH, 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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原文链接：https://blog.csdn.net/qq_32188669/article/details/105197310
