gstreamer - Wadsworth's constant thumbnailer - gstreamer

Question

I'm trying to build a video thumbnailer using gst-python, it looks like this.
from __future__ import division
import sys
import logging
import pdb
_log = logging.getLogger(__name__)
logging.basicConfig()
_log.setLevel(logging.DEBUG)
try:
import gobject
gobject.threads_init()
except:
raise Exception('gobject could not be found')
try:
import pygst
pygst.require('0.10')
import gst
from gst import pbutils
from gst.extend import discoverer
except:
raise Exception('gst/pygst 0.10 could not be found')
class VideoThumbnailer:
'''
Creates a video thumbnail
- Sets up discoverer & transcoding pipeline.
Discoverer finds out information about the media file
- Launches gobject.MainLoop, this triggers the discoverer to start running
- Once the discoverer is done, it calls the __discovered callback function
- The __discovered callback function launches the transcoding process
- The _on_message callback is called from the transcoding process until it
gets a message of type gst.MESSAGE_EOS, then it calls __stop which shuts
down the gobject.MainLoop
'''
def __init__(self, src, dst, **kwargs):
_log.info('Initializing VideoThumbnailer...')
# Set instance variables
self.loop = gobject.MainLoop()
self.source_path = src
self.destination_path = dst
self.destination_dimensions = kwargs.get('dimensions') or (180, 180)
if not type(self.destination_dimensions) == tuple:
raise Exception('dimensions must be tuple: (width, height)')
# Run setup
self._setup()
# Run.
self._run()
def _setup(self):
self._setup_pipeline()
self._setup_discover()
def _run(self):
_log.info('Discovering...')
self.discoverer.discover()
_log.info('Done')
_log.debug('Initializing MainLoop()')
self.loop.run()
def _setup_discover(self):
self.discoverer = discoverer.Discoverer(self.source_path)
# Connect self.__discovered to the 'discovered' event
self.discoverer.connect('discovered', self.__discovered)
def __discovered(self, data, is_media):
'''
Callback for media discoverer.
'''
if not is_media:
self.__stop()
raise Exception('Could not discover {0}'.format(self.source_path))
_log.debug('__discovered, data: {0}'.format(data))
self.data = data
# Run any tasks that depend on the info from the discovery
self._on_discovered()
# Tell the transcoding pipeline to start running
#self.pipeline.set_state(gst.STATE_PLAYING)
_log.info('Transcoding...')
def _on_discovered(self):
self.__setup_capsfilter()
def _setup_pipeline(self):
# Create a new pipeline
self.pipeline = gst.Pipeline('VideoThumbnailerPipeline')
# Create the elements in the pipeline
self.filesrc = gst.element_factory_make('filesrc', 'filesrc')
self.filesrc.set_property('location', self.source_path)
self.pipeline.add(self.filesrc)
self.decoder = gst.element_factory_make('decodebin2', 'decoder')
self.decoder.connect('new-decoded-pad', self._on_dynamic_pad)
self.pipeline.add(self.decoder)
self.ffmpegcolorspace = gst.element_factory_make(
'ffmpegcolorspace', 'ffmpegcolorspace')
self.pipeline.add(self.ffmpegcolorspace)
self.videoscale = gst.element_factory_make('videoscale', 'videoscale')
self.videoscale.set_property('method', 'bilinear')
self.pipeline.add(self.videoscale)
self.capsfilter = gst.element_factory_make('capsfilter', 'capsfilter')
self.pipeline.add(self.capsfilter)
self.jpegenc = gst.element_factory_make('jpegenc', 'jpegenc')
self.pipeline.add(self.jpegenc)
self.filesink = gst.element_factory_make('filesink', 'filesink')
self.filesink.set_property('location', self.destination_path)
self.pipeline.add(self.filesink)
# Link all the elements together
self.filesrc.link(self.decoder)
self.ffmpegcolorspace.link(self.videoscale)
self.videoscale.link(self.capsfilter)
self.capsfilter.link(self.jpegenc)
self.jpegenc.link(self.filesink)
self._setup_bus()
def _on_dynamic_pad(self, dbin, pad, islast):
'''
Callback called when ``decodebin2`` has a pad that we can connect to
'''
# Intersect the capabilities of the video sink and the pad src
# Then check if they have common capabilities.
if not self.ffmpegcolorspace.get_pad_template('sink')\
.get_caps().intersect(pad.get_caps()).is_empty():
# It IS a video src pad.
pad.link(self.ffmpegcolorspace.get_pad('sink'))
def _setup_bus(self):
self.bus = self.pipeline.get_bus()
self.bus.add_signal_watch()
self.bus.connect('message', self._on_message)
def __setup_capsfilter(self):
caps = ['video/x-raw-rgb']
if self.data.videoheight > self.data.videowidth:
# Whoa! We have ourselves a portrait video!
caps.append('height={0}'.format(
self.destination_dimensions[1]))
else:
# It's a landscape, phew, how normal.
caps.append('width={0}'.format(
self.destination_dimensions[0]))
self.capsfilter.set_property(
'caps',
gst.caps_from_string(
', '.join(caps)))
def _on_message(self, bus, message):
_log.debug((bus, message))
t = message.type
if t == gst.MESSAGE_EOS:
self.__stop()
_log.info('Done')
elif t == gst.MESSAGE_ERROR:
_log.error((bus, message))
self.__stop()
def __stop(self):
_log.debug(self.loop)
self.pipeline.set_state(gst.STATE_NULL)
gobject.idle_add(self.loop.quit)
What it does
filesrc loads a video file
decodebin2 demuxes the video file, connects the video src pad to the ffmpegcolorspace sink
ffmpegcolorspace does whatever it does with the color spaces of the video stream
videoscale scales the video
capsfilter tells videoscale to make the video fit in a 180x180 box
jpegenc captures a single frame
filesink saves the jpeg file
What I want it to do
filesrc loads a video file
decodebin2 demuxes the video file, connects the video src pad to the ffmpegcolorspace sink
ffmpegcolorspace does whatever it does with the color spaces of the video stream
videoscale scales the video
capsfilter tells videoscale to make the video fit in a 180x180 box
jpegenc captures a single frame AT 30% INTO THE VIDEO
filesink saves the jpeg file
I've tried with
self.decoder.seek_simple(
gst.FORMAT_PERCENT,
gst.SEEK_FLAG_FLUSH,
self.WADSWORTH_CONSTANT) # int(30)
placed in _on_dynamic_pad, after pad linking, alas to no avail.

Answer 1

This is now implemented in the VideoThumbnailer class in https://github.com/jwandborg/mediagoblin/blob/video_gstreamer-only/mediagoblin/media_types/video/transcoders.py#L53.