python Gstreamer编写mp4视频播放器
对使用Gstreamer编写播放器的理解
使用Gstreamer编写播放器有几个重点：
1.元件的挑选：
根据视频的封装格式和封装内的视频、音频编码格式挑选所需要的解封装和解码元件。视频、音频编码的格式可以从视频的属性中获得：
如图中视频的编码格式为H.264,音频的编码格式为AAC。而相关元件可以使用gst-inspect命令来搜索。
2.元件的连接
元件连接部分重点在设置回调函数在demuxer产生新衬垫时与队列衬垫连接。使用gst-inspect命令可以获得元件衬垫的template，以此区分视频和音频流来完成产生衬垫时的连接。
命令：gst-inspect-1.0 qtdemux
mp4简易播放器：
import gi
gi.require_version('Gst', '1.0')
from gi.repository import Gst, GObject, GLib
Gst.init(None)
#设置回调函数在demuxer产生新衬垫时与队列衬垫连接
def cb_demuxer_newpad(src, pad, dst,dst2):
if pad.get_property("template").name_template == "video_%u":
vdec_pad = dst.get_static_pad("sink")
pad.link(vdec_pad)
elif pad.get_property("template").name_template == "audio_%u":
adec_pad = dst2.get_static_pad("sink")
pad.link(adec_pad)
#创建elements
pipe = Gst.Pipeline.new("test")
src = Gst.ElementFactory.make("filesrc", "src")
demuxer = Gst.ElementFactory.make("qtdemux", "demux")
#创建视频队列元件
decodebin = Gst.ElementFactory.make("avdec_h264", "decode")
queuev = Gst.ElementFactory.make("queue", "queue")
conv = Gst.ElementFactory.make("videoconvert", "conv")
sink = Gst.ElementFactory.make("xvimagesink", "sink")
#创建音频队列元件
decodebina = Gst.ElementFactory.make("faad", "decodea")
queuea = Gst.ElementFactory.make("queue", "queuea")
conva = Gst.ElementFactory.make("audioconvert", "conva")
sinka = Gst.ElementFactory.make("autoaudiosink", "sinka")
#获取播放地址（这里location表示视频和代码在同一个项目下）
src.set_property("location", "a.mp4")
demuxer.connect("pad-added", cb_demuxer_newpad, queuev,queuea)
#向管道中添加元件
pipe.add(src)
pipe.add(demuxer)
pipe.add(queuev)
pipe.add(decodebin)
pipe.add(conv)
pipe.add(sink)
pipe.add(queuea)
pipe.add(decodebina)
pipe.add(conva)
pipe.add(sinka)
#连接元件
src.link(demuxer)
queuev.link(decodebin)
decodebin.link(conv)
conv.link(sink)
queuea.link(decodebina)
decodebina.link(conva)
conva.link(sinka)
#修改状态为播放
pipe.set_state(Gst.State.PLAYING)
mainloop = GLib.MainLoop()
mainloop.run()
带有gtk界面的mp4播放器
import os
import gi
gi.require_version('Gst', '1.0')
gi.require_version('Gtk', '3.0')
from gi.repository import Gst, GObject, Gtk
class GTK_Main(object):
def __init__(self):
window = Gtk.Window(Gtk.WindowType.TOPLEVEL)
window.set_title("Mpeg2-Player")
window.set_default_size(500, 400)
window.connect("destroy", Gtk.main_quit, "WM destroy")
vbox = Gtk.VBox()
window.add(vbox)
hbox = Gtk.HBox()
vbox.pack_start(hbox, False, False, 0)
self.entry = Gtk.Entry()
hbox.add(self.entry)
self.button = Gtk.Button("Start")
hbox.pack_start(self.button, False, False, 0)
self.button.connect("clicked", self.start_stop)
self.movie_window = Gtk.DrawingArea()
vbox.add(self.movie_window)
window.show_all()
self.player = Gst.Pipeline.new("player")
source = Gst.ElementFactory.make("filesrc", "file-source")
demuxer = Gst.ElementFactory.make("qtdemux", "demuxer")
demuxer.connect("pad-added", self.demuxer_callback)
self.video_decoder = Gst.ElementFactory.make("avdec_h264", "video-decoder")
self.audio_decoder = Gst.ElementFactory.make("faad", "audio-decoder")
audioconv = Gst.ElementFactory.make("audioconvert", "converter")
audiosink = Gst.ElementFactory.make("autoaudiosink", "audio-output")
videosink = Gst.ElementFactory.make("xvimagesink", "video-output")
self.queuea = Gst.ElementFactory.make("queue", "queuea")
self.queuev = Gst.ElementFactory.make("queue", "queuev")
colorspace = Gst.ElementFactory.make("videoconvert", "colorspace")
#colorspace = Gst.ElementFactory.make("ffmpegcolorspace", "colorspace")
self.player.add(source)
self.player.add(demuxer)
self.player.add(self.video_decoder)
self.player.add(self.audio_decoder)
self.player.add(audioconv)
self.player.add(audiosink)
self.player.add(videosink)
self.player.add(self.queuea)
self.player.add(self.queuev)
self.player.add(colorspace)
source.link(demuxer)
self.queuev.link(self.video_decoder)
self.video_decoder.link(colorspace)
colorspace.link(videosink)
self.queuea.link(self.audio_decoder)
self.audio_decoder.link(audioconv)
audioconv.link(audiosink)
bus = self.player.get_bus()
bus.add_signal_watch()
bus.enable_sync_message_emission()
bus.connect("message", self.on_message)
bus.connect("sync-message::element", self.on_sync_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)
else:
self.player.set_state(Gst.State.NULL)
self.button.set_label("Start")
def on_message(self, bus, message):
t = message.type
if t == Gst.MessageType.EOS:
self.player.set_state(Gst.State.NULL)
self.button.set_label("Start")
elif t == Gst.MessageType.ERROR:
err, debug = message.parse_error()
print ("Error: %s" % err, debug)
self.player.set_state(Gst.State.NULL)
self.button.set_label("Start")
def on_sync_message(self, bus, message):
if message.get_structure().get_name() == 'prepare-window-handle':
imagesink = message.src
imagesink.set_property("force-aspect-ratio", True)
xid = self.movie_window.get_property('window').get_xid()
imagesink.set_window_handle(xid)
def demuxer_callback(self, demuxer, pad):
if pad.get_property("template").name_template == "video_%u":
qv_pad = self.queuev.get_static_pad("sink")
pad.link(qv_pad)
elif pad.get_property("template").name_template == "audio_%u":
qa_pad = self.queuea.get_static_pad("sink")
pad.link(qa_pad)
Gst.init(None)
GTK_Main()
GObject.threads_init()
Gtk.main()