What is Gstreamer?
GStreamer is a pipeline-based multimedia framework written in C language based on GObject.
By applying GStreamer, the multimedia framework, you can write any kind of streaming applications such as: meidaplayer, audio and video editor, VOIP, streaming media server, audio and video encoding, etc.
Summary of knowledge about fast forward/fast rewind/loop playback of videos:
1. Obtain the local video duration:
Introduction to the official function of .query_duration:
def .query_duration (self, format): #python wrapper for 'gst_pad_query_duration' Queries a pad for the total stream duration. Parameters: pad ( ) –a to invoke the duration query on. format ( ) –the 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.
Use as follows:
pipeline.query_duration()[1]
Where pipeline is the pipeline for playing local videos, the query_duration() function returns a tuple, the form of the tuple is [Ture,duration:******], and ******* is the video duration in units of ns.
2. Get the current location of the video playback:
Introduction to the official function of .query_position:
def .query_position (self, format): #python wrapper for 'gst_pad_query_position' Queries a pad for the stream position. Parameters: pad ( ) –a to invoke the position query on. format ( ) –the 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.
Use method and duration to get functionquery_duration()same.
3. Play the jump function:
.seek_simple official function introduction:
def .seek_simple (self, format, seek_flags, seek_pos): #python wrapper for 'gst_element_seek_simple' Parameters: element ( ) –a to seek on format ( ) –a to execute the seek in, such as seek_flags ( ) –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 this value is in nanoseconds - multiply with to convert seconds to nanoseconds or with to convert milliseconds to nanoseconds. Returns ( gboolean ) : TRUE (not introspectable) if the seek operation succeeded. Flushing seeks will trigger a preroll, which will emit .ASYNC_DONE.
Function usage example:
pipeline.seek_simple(, , time)
The unit of time is nanoseconds.
A small player with video fast forward/fast backward/loop playback functions.
import os, _thread, time
import gi
gi.require_version("Gst", "1.0")
gi.require_version('Gtk', '3.0')
from import Gst, GObject, Gtk, Gdk
class GTK_Main:
def __init__(self):
window = ()
window.set_title("Vorbis-Player")
window.set_default_size(500, -1)
("destroy", Gtk.main_quit, "WM destroy")
vbox = ()
(vbox)
= ()
vbox.pack_start(, False, False, 0)
hbox = ()
(hbox)
buttonbox = ()
hbox.pack_start(buttonbox, False, False, 0)
rewind_button = ("Rewind")
rewind_button.connect("clicked", self.rewind_callback)
(rewind_button)
= ("Start")
("clicked", self.start_stop)
()
forward_button = ("Forward")
forward_button.connect("clicked", self.forward_callback)
(forward_button)
self.time_label = ()
self.time_label.set_text("00:00 / 00:00")
(self.time_label)
window.show_all()
= ("player")
source = ("filesrc", "file-source")
demuxer = ("decodebin", "demuxer")
videoconv = ("videoconvert", "converter")
videosink = ("xvimagesink", "video-output")
("pad-added", self.demuxer_callback, videoconv)
for ele in [source, demuxer, videoconv, videosink]:
(ele)
(demuxer)
(videosink)
bus = .get_bus()
bus.add_signal_watch()
("message", self.on_message)
def start_stop(self, w):
if .get_label() == "Start":
filepath = .get_text().strip()
if (filepath):
filepath = (filepath)
.set_label("Stop")
.get_by_name("file-source").set_property("location", filepath)
.set_state()
self.play_thread_id = _thread.start_new_thread(self.play_thread, ())
else:
self.play_thread_id = None
.set_state()
.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:
(0.2)
dur_int = .query_duration()[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
(0.2)
while play_thread_id == self.play_thread_id:
pos_int = .query_position()[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()
(1)
def on_message(self, bus, message):
t =
if t == :
.seek_simple(, , 0000000000)
elif t == :
err, debug = message.parse_error()
print ("Error: %s" % err, debug)
self.play_thread_id = None
.set_state()
.set_label("Start")
self.time_label.set_text("00:00 / 00:00")
def demuxer_callback(self, demuxer, pad, dst):
caps = .get_current_caps(pad)
structure_name = caps.to_string()
if structure_name.startswith("video"):
videorate_pad = dst.get_static_pad("sink")
(videorate_pad)
def rewind_callback(self, w):
rc, pos_int = .query_position()
seek_ns = pos_int - 10 * 1000000000
if seek_ns < 0:
seek_ns = 0
print ('Backward: %d ns -> %d ns' % (pos_int, seek_ns))
.seek_simple(, , seek_ns)
def forward_callback(self, w):
rc, pos_int = .query_position()
seek_ns = pos_int + 10 * 1000000000
print ('Forward: %d ns -> %d ns' % (pos_int, seek_ns))
.seek_simple(, , 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()
(None)
GTK_Main()
()
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