Old python code for transcoding images

image_transcoding.py

"""
Helpers to transcode images.

DEPENDENCIES
------------
imagemagick     (for converting, already installed)
avconv          (for transcoding)           sudo apt-get install libav-tools
libx264         (higher encoding quality)   sudo apt-get install libavcodec-extra-53

http://askubuntu.com/questions/266663/ffmpeg-resize-could-not-find-codec-parameters
"""

from __future__ import absolute_import

import os
import time
import logging
import subprocess
from glob import glob
from tempfile import NamedTemporaryFile
from apps.services.aws.s3 import s3_bucket

from django.conf import settings


log = logging.getLogger(__name__)

STORAGE_DIR = '/percolate/hotlanta/apps/ugc/transcode/image/transcoded/'


def start_job(keyname, filename):  # creator?
    """
    Start a transcoding job using the given image file keyname

    Args:
        keyname (str) - key name of the image file to transcode
        filename (str) - the name of the image file

    """
    timestamp = str(time.time())
    log.debug("native transcode job started for: " + keyname)

    with s3_bucket(settings.S3_CLIENT_UPLOAD_BUCKET) as image_bucket, NamedTemporaryFile() as fp:
        key = image_bucket.get_key(keyname)
        key.get_contents_to_filename(fp.name)

        f = os.path.splitext(os.path.basename(filename))[0]

        if filename.endswith(".gif"):
            # handle gif:
            _convert_gif_to_mp4(fp.name, f)
            _update_find_a_better_name()  # store video on db + s3
        else:
            # handle img:
            _convert_img_to_jpg(fp.name, f)
            # replace img with jpg (db)


def _convert_gif_to_mp4(gif_path, mp4_name, quality=23):
    """
    Converts a GIF to an MP4 and stores the result

    Args:
        gif_path (str) - the path to the gif file to convert
        mp4_name (str) - the desired name of the resultant mpeg4 file
        quality (int) - the desired quality of the resultant mpeg4 file

    PLEASE NOTE:
    Once Percolate updates to a more recent Ubuntu release, FFmpeg (the real one) can be used
    and ALL of the code contained in this function can be substituted with one line, as follows:
    subprocess.call('ffmpeg -i {0} -pix_fmt yuv420p -vf scale=trunc(iw/2)*2:trunc(ih/2)*2 \
    {1}.mp4'.format(gif_path, mp4_name).split())
    """

    ticks_per_frame = subprocess.check_output('identify -verbose -format %T_ {0}'.format(gif_path).split()).split('_')[:-1]
    ticks_per_frame = [int(i) for i in ticks_per_frame]
    num_frames = len(ticks_per_frame)
    min_ticks = min(ticks_per_frame)

    subprocess.call('convert -coalesce {0} tmp%d.png'.format(gif_path).split())

    if len(set(ticks_per_frame)) > 1:
        num_dup = 0
        num_dup_total = 0
        for frame, ticks in enumerate(ticks_per_frame):
            num_dup_total += num_dup
            frame += num_dup_total
            num_dup = 0
            if ticks > min_ticks:
                num_dup = (ticks / min_ticks) - 1
                for i in range(num_frames + num_dup_total - 1, frame, -1):
                    orig = 'tmp%d.png' % i
                    new = 'tmp%d.png' % (i + num_dup)
                    subprocess.call(['mv', orig, new])
                for i in range(1, num_dup + 1):
                    curr = 'tmp%d.png' % frame
                    dup = 'tmp%d.png' % (i + frame)
                    subprocess.call(['cp', curr, dup])

    framerate = (100 / min_ticks) if min_ticks else 10

    subprocess.call('avconv -r {0} -i tmp%d.png -c:v libx264 -crf {1} -pix_fmt yuv420p \
    -vf scale=trunc(iw/2)*2:trunc(ih/2)*2 -y {2}.mp4'.format(framerate, quality, STORAGE_DIR + mp4_name).split())

    subprocess.call(['rm'] + glob('tmp*.png'))


def _convert_img_to_jpg(img_path, jpg_name):
    """
    Converts an img file to a JPG and stores the result

    Args:
        img_file (str) - the path to the image file to convert
        jpg_name (str) - the desired name of the resultant jpeg file

    """
    # If this is going to remain a single line, might as well stick it in start_job
    subprocess.call('convert {0} {1}.jpg'.format(img_path, STORAGE_DIR + jpg_name).split())