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• H264 decompression/decomposition into JPG - quality issues

  5 juin 2013, par Respectech

  I'm trying to decode a 1920x1080 30fps h264 stream. Individual frames look outstanding in VLC media player (pausing the playback), but when I decode using avconv (ffmpeg has been deprecated and replaced by avconv), the frame quality is really poor by comparison (my primary complaint is blockiness).

  Here's how I am calling avconv :

  avconv -i video.h264 -s 1920x1080 -f image2 temp/images/video-%03d.jpg

  Is there a jpg output setting for avconv ? I read what I suspected were the salient parts of the avconv documentation (namely, http://libav.org/avconv.html#image2-1), and couldn't find any way to specify the output jpg quality.

  In addition, it appears avconv reads the entire stream before it starts decoding it, so if the stream is in progress, it only decodes to where the stream was when avconv started the decoding process. Is there any way around this ? In other words, if a 10-second-long stream is started at t seconds and avconv is started at t+1 seconds, avconv will only decode 1 second of the stream.

• Split a movie so that each GIF is under a certain file size

  9 novembre 2014, par Terence Eden

  Problem

  I want to convert a long movie into a series on animated GIFs.

  Each GIF needs to be <5MB.

  Is there any way to determine how large a GIF will be while it is being encoded ?

  Progress So Far

  I can split the movie into individual frames :

  ffmpeg -i movie.ogv -r 25 frameTemp.%05d.gif

  I can then use convert from ImageMagick to create GIFs. However, I can’t find a way to determine the likely file size before running the command.

  Alternatively, I can split the movie into chunks :

  ffmpeg -i movie.ogv -vcodec copy -ss 00:00:00 -t 00:20:00 output1.ogv

  But I’ve no way of knowing if, when I convert the file to a GIF it will be under 5MB.

  A 10 second scene with a lot of action may be over 5MB (bad !) and a static scene could be under 5MB (not a problem, but not very efficient).

  Ideas

  I think that what I want to do is convert the entire movie into a GIF, then find a way to split it by file size.

  Looking at ImageMagick, I can split a GIF into frames, but I don’t see a way to split it into animated GIFs of a certain size / length.

  So, is this possible ?

• Converting mkv files to mp4 with ffmpeg-python [closed]

  22 août, par myth0s

  I have a lot of .mkv files that I'm trying to convert to .mp4, so I decided to try and program a solution in python. After a few hours, trying to figure out how to copy the subfolders too, I gave up on it and decided to stick with converting individual subfolders, and then copying them over to another directory.

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  I've made a simple script, that should convert .mkv files that are in the same folder as the script. However, I keep getting this error :

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  FileNotFoundError : [WinError 2] The system cannot find the file specified

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  Here's my code :

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  import os
import ffmpeg

start_dir = os.getcwd()

def convert_to_mp4(mkv_file):
    no_extension = str(os.path.splitext(mkv_file))
    with_mp4 = no_extension + ".mp4"
    ffmpeg.input(mkv_file).output(with_mp4).run()
    print("Finished converting {}".format(no_extension))

for path, folder, files in os.walk(start_dir):
    for file in files:
        if file.endswith('.mkv'):
            print("Found file: %s" % file)
            convert_to_mp4(file)
        else:
            pass



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