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• slowing down a video with ffmpeg

  20 août 2014, par jeet

  I’m making a video using ffmpeg & multiple images with this command :

  ffmpeg -f image2 -i img%d.png v.mpg

  The video is made, but plays very fast. Can I slow it down a bit ? (double duration nearly)
  If possible set the speed while creation itself please.

  I also need to add an audio "a.wav" to the video being made, possibly in the same command. Is that possible ?

  Please give me the commands
  Thanks

  When I use this command, below is the error I get :

  ffmpeg -r 12 -i pic\s%d.png -i rmt.wav -shortest -r 25 v.mpg
  
  
  
  
  
  
  
  FFmpeg version SVN-r16573, Copyright (c) 2000-2009 Fabrice Bellard, et al.
  
  configuration: --extra-cflags=-fno-common --enable-memalign-hack --enable-pthreads --enable-libmp3lame --enable-libxvid --enable-libvorbis --enable-libtheora --enable-libspeex --enable-libfaac --enable-libgsm --enable-libx264 --enable-libschroedinger --enable-avisynth --enable-swscale --enable-gpl
  
  libavutil     49.12. 0 / 49.12. 0
  
  libavcodec    52.10. 0 / 52.10. 0
  
  libavformat   52.23. 1 / 52.23. 1
  
  libavdevice   52. 1. 0 / 52. 1. 0
  
  libswscale     0. 6. 1 /  0. 6. 1
  
  built on Jan 13 2009 02:57:09, gcc: 4.2.4
  
  Input #0, image2, from 'pic\s%d.png':
  
  Duration: 00:03:53.00, start: 0.000000, bitrate: N/A
  
  Stream #0.0: Video: png, rgb24, 1366x768, 12.00 tb(r)
  
  Input #1, wav, from 'rmt.wav':
  
  Duration: 00:12:16.19, bitrate: 64 kb/s
  
  Stream #1.0: Audio: pcm_u8, 8000 Hz, mono, s16, 64 kb/s
  
  Stream #0.0: Video: mpeg1video, yuv420p, 1366x768, q=2-31, 200 kb/s, 25.00 tb(c)
  
  Stream #0.1: Audio: mp2, 8000 Hz, mono, s16, 64 kb/s
  
  Stream mapping:
  
  Stream #0.0 -> #0.0
  
  Stream #1.0 -> #0.1
  
  [mp2 @ 0x1738390]Sampling rate 8000 is not allowed in mp2
  
  Error while opening codec for output stream #0.1 - maybe incorrect parameters such as bit_rate, rate, width or height

• Video length missing in FLV converted by ffmpeg-php

  19 janvier 2013, par Andrew

  I'm converting MP4 videos to FLV using ffmpeg-php on my CentOS server (without intervention from flvtool2 because it's not installed).

  The FLV videos are created, but no player is capable of retrieving the video duration, this creates serious issues when trying to seek the video. I'm using the player created by Moyea's Flash Video MX Pro, but the problem also happens with other FLV players as well, so I'm sure that ffmpeg-php is not createing the FLV with the proper length data.

  My MP4 videos are compatible because ffmpeg-php CAN get the video length properly from then, yet it does not apply that length information into the FLV file. I assume flvtool2 is ONLY to retrieve meta-data and has nothing to do with the output FLV video length, let me know if this is correct.

  This command I use for conversion :

  $command = "ffmpeg -i myvideo.mp4 -ar 22050 -ab 64k -f flv -s 320x240 -y myvideo.flv";
  
  $result = @shell_exec($command);

  This is my ffmpeg-php version :

  FFmpeg version 0.5, Copyright (c) 2000-2009 Fabrice Bellard, et al.
  
    configuration: --prefix=/usr --libdir=/usr/lib64 --shlibdir=/usr/lib64 --mandir=/usr/share/man --incdir=/usr/include --extra-cflags=-fPIC --enable-libamr-nb --enable-libamr-wb --enable-libdirac --enable-libfaac --enable-libfaad --enable-libmp3lame --enable-libtheora --enable-libx264 --enable-gpl --enable-nonfree --enable-postproc --enable-pthreads --enable-shared --enable-swscale --enable-x11grab
  
    libavutil     49.15. 0 / 49.15. 0
  
    libavcodec    52.20. 0 / 52.20. 0
  
    libavformat   52.31. 0 / 52.31. 0
  
    libavdevice   52. 1. 0 / 52. 1. 0
  
    libswscale     0. 7. 1 /  0. 7. 1
  
    libpostproc   51. 2. 0 / 51. 2. 0
  
    built on Jul 24 2009 01:40:27, gcc: 4.1.2 20080704 (Red Hat 4.1.2-44)

  Any help on this issue will be greatly appreciated.

• What Every Programmer Should Know

  24 décembre 2012, par Multimedia Mike — General

  During my recent effort to force myself to understand Unicode and modern text encoding/processing, I was reminded that this is something that “every programmer should just know”, an idea that comes up every so often, usually in relation to a subject in which the speaker is already an expert. One of the most absurd examples I ever witnessed was a blog post along the lines of “What every working programmer ought to know about [some very specific niche of enterprise-level Java programming]“. I remember reading through the article and recognizing that I had almost no knowledge of the material. Disturbing, since I am demonstrably a “working programmer”.

  For fun, I queried the googles on the matter of what ever programmer ought to know.

  Specific Topics
  Here is what every programmer should know about : Unicode, time, memory (simple), memory (extremely in-depth), regular expressions, search engine optimization, floating point, security, basic number theory, race conditions, managed C++, VIM commands, distributed systems, object-oriented design, latency numbers, rate monotonic algorithm, merging branches in Mercurial, classes of algorithms, and human names.

  Broader Topics
  20 subjects every programmer should know, 97 things every programmer should know, 12 things every programmer should know, things every programmer should know (27 items), 10 papers every programmer should read at least twice, 10 things every programmer should know for their first job.

  Meanwhile, I remain fond of this xkcd comic whose mouseover text describes all that a person genuinely needs to know. Still, the new year is upon us, a time when people often make commitments to bettering themselves, and it couldn’t hurt (much) to at least skim some of the lists and find out what you never knew that you never knew.

  What About Multimedia ?
  Reading the foregoing (or the titles of the foregoing pieces), I naturally wonder if I should write something about what every programmer should know about multimedia. I think it would look something like a multimedia programming FAQ. These are some items that I can think of :

  1. YUV : The other colorspace (since most programmers are only familiar with RGB and have no idea what to make of the YUV that comes out of most video decoding APIs)
  2. Why you can’t easily seek randomly to any specific frame in a video file (keyframe/interframe discussion and their implications)
  3. Understand your platform before endeavoring to implement multimedia software (modern platforms, particularly mobile platforms, probably provide everything you need in the native APIs and there is likely little reason to compile libavcodec for the platform)
  4. Difference between containers and codecs (longstanding item, but I would argue it’s less relevant these days due to standardization on the MPEG — MP4/H.264/AAC — stack)
  5. What counts as a multimedia standard in this day and age (comparing the foregoing MPEG stack with the WebM/VP8/Vorbis stack)
  6. Trade-offs to consider when engineering a multimedia solution
  7. Optimization doesn’t always work the way you think it does (not everything touted as a massive speed-up in the world of computing — whether it be multithreaded CPUs, GPGPUs, new SIMD instruction sets — will necessarily be applicable to multimedia processing)
  8. A practical guide to legal issues would not be amiss
  9.  ???

  What other items count as “something multimedia-related that every programmer should know” ?