RetroAND transcoder... Brillaint

retroand_trans.py

import os
import time
from multiprocessing import Event, Process, Pipe
from Queue import Queue

from retroand.config import cfg
from retroand.log import logger


def transcode_process(connection, path, stop, format='mp3', bitrate=False):
    import pygst
    pygst.require('0.10')
    import gst

    # Check to make sure the bitrate is actually a number
    try:
        bitrate = int(bitrate)
    except:
        bitrate = False
    log_message = "Transcoding %s to %s" % (path.encode(cfg['ENCODING']), format)
    # Make the trans pipeline using these strings
    transcoder = gst.parse_launch(pipeline[format])
    # Bitrate needs to be given and set. Don't worry about the low quality sets
    if bitrate in [40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320]:
        log_message += " at %d kbps" % bitrate
        encoder = transcoder.get_by_name('encoder')
        muxer = transcoder.get_by_name('muxer')
        if format is 'mp3':
            encoder.set_property("target", "bitrate")
            encoder.set_property("bitrate", bitrate)
        elif format is 'ogg':
            encoder.set_property("max-bitrate", bitrate * 1024)
        elif format is 'm4a':
            encoder.set_property("bitrate", bitrate * 1000)

    # Put the file into the transcoder
    log_message += "."
    logger.info(log_message)
    source = transcoder.get_by_name('source')
    try:
        source.set_property("location", path.encode('utf-8'))
        # Make the output asynchronous so that everything fires up fast
        # instead of in real time.
        output = transcoder.get_by_name('output')
        output.set_property("sync", False)
        # Get data from pipe start
        transcoder.set_state(gst.STATE_PLAYING)
        transcoder.get_state()
        try:
            # Send chunks to the client that are encoded
            while True:
                output_buffer = output.emit('pull-buffer')
                if output_buffer and not stop.is_set():
                    connection.send(output_buffer.data)
                else:
                    break
        except:
            logger.warn("Transcoding Error.")
    except:
        logger.error("Failed to open file for transcoding. Check for non-ascii characters?")
    finally:
        try:
            # Try this so it can free the memory used by the transcoder
            transcoder.set_state(gst.STATE_NULL)
        except:
            pass
        if not stop.is_set():
            connection.send(False)
            connection.close()

class Transcoder:
    def __init__(self):
        self.stopping = Event()
    
    def stop(self):
        logger.debug("Preventing new transcoding processes.")
        self.stopping.set()
        
    def transcode(self, path, format='mp3', bitrate=False):
        if self.stopping.is_set():
            return
        try:
            stop = Event()
            start_time = time.time()
            parent_connection, child_connection = Pipe()
            process = Process(target=transcode_process,
                    args=(child_connection, path, stop, format, bitrate))
            process.start()
            while not (self.stopping.is_set() or stop.is_set()):
                data = parent_connection.recv()
                if not data:
                    break
                yield data
            logger.debug("Transcoded %s in %0.2f seconds." % (path.encode(cfg['ENCODING']), time.time() - start_time))
        except GeneratorExit:
            stop.set()
            logger.debug("User canceled the request during transcoding.")
        except:
            stop.set()
            logger.warn("Some type of error occured during transcoding.")
        finally:
            parent_connection.close()
            process.join()

pipeline = {
    'mp3': "filesrc name=source ! decodebin ! audioconvert ! lamemp3enc name=encoder ! id3mux name=muxer ! appsink name=out",
    'ogg': "filesrc name=source ! decodebin ! audioconvert ! vorbisenc name=encoder ! oggmux name=muxer ! appsink name=out",
    'm4a': "filesrc name=source ! decodebin ! audioconvert ! ffenc_aac name=encoder ! ffmux_mp4 name=muxer ! appsink name=out"
}

# Windows port of gstreamer is missing id3mux and id3v2mux. Lets try and use ffmux_mp3.
if os.name == "nt":
    pipeline['mp3'] = "filesrc name=source ! decodebin ! audioconvert ! lamemp3enc name=encoder ! ffmux_mp3 name=muxer ! appsink name=out"