Page 1 of 2 12 LastLast
Results 1 to 10 of 11

Thread: help with avconv and libx264

  1. #1
    Join Date
    Jan 2009
    Beans
    199

    help with avconv and libx264

    Dear all,
    I have to make some videos out of certain simulations I have run.
    The videos are really simple, contain few colors, a lot of the images is
    still, and last only 30sec (at 25fps). I guess I should be able to get a good quality video and a decent filesize.

    I've tried a lot, but I can't get the right settings to get good quality
    videos using avconv.

    There are two kind of conversion that I need to do: one is to crop certain videos that I already have (not made by me)

    Code:
     avconv -y -f avi -c:v h264 -i input_file.avi -f avi -me_method full -c:v libx264 -c:a n -b 512k -qcomp 0.5  -r 50 -vf crop=395:395:135:35 output_file.avi
    The other is to produce movies from a sequence of images:

    Code:
     avconv -y -f avi -c:v h264 -i img%04d.png -f avi -me_method full -c:v libx264 -c:a n -b 512k -qcomp 0.5  -r 50 -s 480x320 output_file.avi
    The size would be also ok, (about 5mb, even though I'd prefer a smaller file), but the quality is not that good.. there are pixels around the contours, the resolution is not that good...

    Could you please give me some good advice on how to set the parameters right? (and can you explain me also what they do, and why mine are wrong???)

    Thanks a lot in advance for the help,
    Cheers, -Luca

  2. #2
    Join Date
    Jan 2010
    Beans
    10

    Re: help with avconv and libx264

    For the second one:

    avconv -y -f avi -c:v h264 -i img%04d.png -f avi -me_method full -c:v libx264 -c:a n -b 512k -qcomp 0.5 -r 50 -s 480x320 output_file.avi
    First of all, don't use AVI, ever, unless you really need to. Use MP4 instead.

    Secondly, that bitrate is really low, which is why they look poor.

    Try something much simpler, and then go from there:

    avconv -y -c:v h264 -i img%04d.png -c:v libx264 -c:a n -r 50 -s 480x320 output_file.mp4

  3. #3
    Join Date
    Jan 2009
    Beans
    199

    Re: help with avconv and libx264

    Hi Beandog,
    first of all thanks for the help.
    Unfortunately I am forced to use .avi, as it is a requirement of the journal.
    Using higher bitrates I get too big files, though.
    In any case I'll try your command, but then I don't know which are the possible parameters that determine a good compromise between the quality
    of the video and its size.
    Any suggestions?
    Thanks a lot for the help,
    Luca

  4. #4
    Join Date
    Jan 2010
    Beans
    10

    Re: help with avconv and libx264

    Quote Originally Posted by lucacerone View Post
    Hi Beandog,
    first of all thanks for the help.
    Unfortunately I am forced to use .avi, as it is a requirement of the journal.
    Using higher bitrates I get too big files, though.
    In any case I'll try your command, but then I don't know which are the possible parameters that determine a good compromise between the quality
    of the video and its size.
    Any suggestions?
    Thanks a lot for the help,
    Luca
    Using x264, it'll default to a quality level of 23, which is pretty good. It goes from 0 to 51, with the smaller numbers being bigger quality (and much bigger size). I wouldn't go above 20. You can change the value with -crf

    So, "ffmpeg -i input -crf 20 output.avi" would change it to 20

    Other than that, I'd try a better x264 preset, which you can pass with -vpre

    For example,

    ffmpeg -i input -crf 20 -vpre slow output.avi

    There's some good ffmpeg x264 encoding guides out there, just look around.

  5. #5
    Join Date
    Jan 2009
    Beans
    199

    Re: help with avconv and libx264

    Thanks again!
    The things that bothers me about the presets is that they seem to be changed at every new version, that is not ideal! (at least the name have changed since my first encoded video).
    Also, I'd rather use avcon than ffmpeg (ubuntu says it is deprecated) would your advices still hold?
    Cheers, -Luca

  6. #6
    Join Date
    Jan 2010
    Beans
    10

    Re: help with avconv and libx264

    Quote Originally Posted by lucacerone View Post
    Thanks again!
    The things that bothers me about the presets is that they seem to be changed at every new version, that is not ideal! (at least the name have changed since my first encoded video).
    Also, I'd rather use avcon than ffmpeg (ubuntu says it is deprecated) would your advices still hold?
    Cheers, -Luca
    Eh, the presets don't really change.

    avconv (libav) is fine, they use the same syntax for the most part

  7. #7
    Join Date
    Jan 2009
    Beans
    199

    Re: help with avconv and libx264

    Thanks for the advices,
    actually I've found your page on the Gentoo website,
    so at least now I know which presets are in use and what values they use
    As I have found some presets to encode to tablets etc etc, where should I put
    these presets to have them both only for me, both system-wide?

    Thanks a lot, again!

  8. #8
    Join Date
    Sep 2006
    Beans
    3,710

    Re: help with avconv and libx264

    Quote Originally Posted by lucacerone View Post
    The things that bothers me about the presets is that they seem to be changed at every new version
    The preset system has gone through some changes, and although it can be frusutrating to users in the long run the changes have been good. The old x264 preset files were depreciated and removed because presets are now accessed directly via libx264.

    Quote Originally Posted by lucacerone View Post
    As I have found some presets to encode to tablets etc etc, where should I put
    these presets to have them both only for me, both system-wide?
    You should not simply copy preset files and expect them to work with ffmpeg. This is a common misconception. The presets are very specific to the version of ffmpeg that they come with. You should only use the presets that come with your version of ffmpeg. Kind of a moot point now since recent ffmpeg now uses the actual x264 presets instead of emulating them with a text file.

    General usage is to:
    1. Choose your crf value as beandog explained. A lower value is a higher quality. A sane range is 18-28. Use the highest value that still looks good to you.
    2. Use the slowest preset you have patience for. A preset is a collection of options that gives a certain encoding speed/compression ratio. See "x264 --help" for a list of available presets and ignore the "placebo" preset as it is a waste of time.
    3. Use these settings for the rest of your set of videos.


    Example:
    Code:
    ffmpeg -i img%04d.png -c:v libx264 -preset slow -crf 24 output
    You don't need -me_method or -qcomp. The preset will take care of the details. Also remove the "-f avi -c:v h264" before your -i. Options before -i are intended as input options and in this case you're telling ffmpeg to decode the png images as H.264.

  9. #9
    Join Date
    May 2012
    Beans
    2

    Re: help with avconv and libx264

    Thanks but if the image sequence file numbering doesn't start with 0 or 1 this command doesn't work.

    I have lots of sequence files that I'd like to convert to high quality MP4. Unfortunately the numbering of the files don't always start with 0 or 1. For example

    sc_101a1050.png
    ...
    ...
    sc_101a1100.png

    How to correctly use the %04d as parameter for the avconv command?
    When I try the command gave me this error:
    ---------------------
    $ avconv -f image2 -i sc_101a%04d.png -r 30 -crf 20 -c:v libx264 output.mp4
    avconv version 0.8.3-4:0.8.3-0ubuntu0.12.04.1, Copyright (c) 2000-2012 the Libav developers
    built on Jun 12 2012 16:37:58 with gcc 4.6.3
    sc_101a%04d.png: No such file or directory
    --------------------

    Any chance to change and fix the command so that it'll work on any file numbering?

    Thanks in advance:
    Last edited by rabit1; October 3rd, 2012 at 06:06 AM.

  10. #10
    Join Date
    Feb 2008
    Beans
    11

    Re: help with avconv and libx264

    beandog.....your an idiot. everyone in the linux world firstly gives an answer to my question -how to convert mkv to avi, to use this that but only a few mention avconv. secondly everyone wants to ignore the avi for this mkv crap. HELLO...some of us have dvd players that play avi....NOT sh&*^)(, F(*&(&*king MKV. I have three divx players and avi's look and play nicely....I'm not going to spend another 300-500 bucks buying new players. AVI's are excellent....freaking idiots

Page 1 of 2 12 LastLast

Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •