用gstreamer实现音视频同步的代码

以下是一个简单的用 GStreamer 实现音视频同步的示例代码：

import gi
gi.require_version('Gst', '1.0')
from gi.repository import Gst, GObject

GObject.threads_init()
Gst.init(None)

player = Gst.ElementFactory.make("playbin", "player")
player.set_property("uri", "file:///path/to/media/file")

audio_sink = Gst.ElementFactory.make("autoaudiosink", "audio_sink")
video_sink = Gst.ElementFactory.make("autovideosink", "video_sink")

player.set_property("audio-sink", audio_sink)
player.set_property("video-sink", video_sink)

bus = player.get_bus()

def on_message(bus, message):
    t = message.type
    if t == Gst.MessageType.EOS:
        player.set_state(Gst.State.NULL)
        loop.quit()
    elif t == Gst.MessageType.ERROR:
        err, debug = message.parse_error()
        print ("Error: %s" % err, debug)
        player.set_state(Gst.State.NULL)
        loop.quit()
    elif t == Gst.MessageType.STATE_CHANGED:
        if message.src == player:
            old_state, new_state, pending_state = message.parse_state_changed()
            if new_state == Gst.State.PLAYING:
                # Get the current time when playing starts
                query = Gst.Query.new_seeking(Gst.Format.TIME)
                if player.query(query):
                    _, start, _ = query.parse_seeking()
                    global start_time
                    start_time = start

    elif t == Gst.MessageType.QOS:
        # Get the running time of the pipeline
        query = Gst.Query.new_position(Gst.Format.TIME)
        if player.query(query):
            _, running_time = query.parse_position()
            running_time += start_time

            # Get the running time of the last buffer
            struct = message.get_structure()
            _, running_time_buffer, _ = struct.get("running-time")
            running_time_buffer += start_time

            # Calculate the difference between the two running times
            diff = running_time - running_time_buffer

            # If the difference is too big, seek to the correct position
            if abs(diff) > Gst.SECOND / 10:
                player.seek_simple(Gst.Format.TIME, Gst.SeekFlags.FLUSH | Gst.SeekFlags.KEY_UNIT, running_time)

bus.add_signal_watch()
bus.connect("message", on_message)

# Start playing
player.set_state(Gst.State.PLAYING)

# Start the main loop
loop = GObject.MainLoop()
loop.run()

此示例中使用了 `autoaudiosink` 和 `autovideosink` 作为音视频的输出，你还可以将其替换为其他的 sink。在收到 QOS 消息时，获取管道的当前时间以及最后一个缓冲区的运行时间，并在两个运行时间之间计算差异，如果差异太大，则使用 `seek_simple()` 函数跳转到正确的位置，以保持音视频同步。