Gstreamer+python:在管道运行时添加和删除音频源

Question

我正在编写一个示例python脚本，最初可以在这里找到：Adding and removing audio sources to/from GStreamer pipeline on-the-go。 其目的是制作一个像上面这样的脚本，能够在管道运行时插入和删除音频源，但是在源和加法器之间有一个audioconvert元素。这是因为在更一般的情况下，加法器希望传入的流具有相同的格式。在

代码是这样的，我们创建了两个发电机（蜂鸣器）。第一个发出1000赫兹的音调并等待返回键。第二个是500Hz的音调，在按键之后，它被加在第一个音调上。再次按下返回键，只听到第二个发电机的声音。在

#!/usr/bin/python

import gobject;
gobject.threads_init()
import gst

# THE FOLLOWING FUNCTION IS A REWORK OF THE ORIGINAL, STILL DOING THE JOB

def create_raw_audiotest_signal(pipe, freq, adder):
  # create buzzer of a given freq
  buzzer = gst.element_factory_make("audiotestsrc","buzzer%d" % freq)
  buzzer.set_property("freq",freq)
  pipe.add(buzzer)
  buzzersrc=buzzer.get_pad("src")
  # Gather a request sink pad on the mixer
  sinkpad=adder.get_request_pad("sink%d")
  # .. and connect it to the buzzer
  buzzersrc.link(sinkpad)
  return buzzer, buzzersrc, sinkpad

# THIS IS A MODIFIED VERSION, NOT WORKING, THAT JUST PUTS AN AUDIOCONVERT
# ELEMENT BETWEEN THE GENERATOR AND THE ADDER.

def create_audiotest_signal_with_converter(pipe, freq, adder):
    # create buzzer of a given freq
    buzzer = gst.element_factory_make("audiotestsrc","buzzer%d" % freq)
    buzzer.set_property("freq",freq)
    # add a converter because adder wants inputs with the same format.
    ac = gst.element_factory_make("audioconvert", "ac%d" % freq)
    pipe.add(buzzer, ac)
    # link the buzzer with the converter ...
    buzzer.link(ac)
    buzzersrc=buzzer.get_pad("src")
    # Gather a request sink pad on the mixer
    sinkpad=adder.get_request_pad("sink%d")
    # and then the converter to the adder
    ac.get_pad('src').link(sinkpad)
    return buzzer, buzzersrc, sinkpad

if __name__ == "__main__":
  # First create our pipeline
  pipe = gst.Pipeline("mypipe")

  # Create a software mixer with "Adder"
  adder = gst.element_factory_make("adder","audiomixer")
  pipe.add(adder)

  # Create the first buzzer..
  #buzzer1, buzzersrc1, sinkpad1 = create_raw_audiotest_signal(pipe, 1000, adder)
  buzzer1, buzzersrc1, sinkpad1 = create_audiotest_signal_with_converter(pipe, 1000, adder)

  # Add some output
  output = gst.element_factory_make("autoaudiosink", "audio_out")
  pipe.add(output)
  adder.link(output)

  # Start the playback
  pipe.set_state(gst.STATE_PLAYING)

  raw_input("1kHz test sound. Press <ENTER> to continue.")

  # Get another generator
  #buzzer2, buzzersrc2, sinkpad2 = create_raw_audiotest_signal(pipe, 500, adder)
  buzzer2, buzzersrc2, sinkpad2 = create_audiotest_signal_with_converter(pipe, 500, adder)

  # Start the second buzzer (other ways streaming stops because of starvation)
  buzzer2.set_state(gst.STATE_PLAYING)

  raw_input("1kHz + 500Hz test sound playing simoultenously. Press <ENTER> to continue.")

  # Before removing a source, we must use pad blocking to prevent state changes
  buzzersrc1.set_blocked(True)
  # Stop the first buzzer
  buzzer1.set_state(gst.STATE_NULL)
  # Unlink from the mixer
  buzzersrc1.unlink(sinkpad2)
  # Release the mixers first sink pad
  adder.release_request_pad(sinkpad1)
  # Because here none of the Adder's sink pads block, streaming continues

  raw_input("Only 500Hz test sound. Press <ENTER> to stop.")

如果您在两个调用中使用create_raw audiotest_signal来代替使用_converter创建_audiotest_signal_，当然可以工作。如果你使用两者的混合，它是有效的，但中间有一个不必要的额外延迟。最有趣的情况是在两个调用中都使用audioconvert，但是gtk在第一个return键处阻塞。在

有人有什么建议吗？我做错什么了？ 提前谢谢你。在

Answer 1

我自己找到了答案，其实很简单。。。 我添加了其他组件，但它们仍在管道中，并保持独立的播放状态。因此，解决方案是将所有管道设置为playing，然后将状态设置为所有子级。在

管道设置状态(国税局游戏)

而不是：

蜂鸣器2.设置状态(国税局游戏)

它又起作用了。在