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• Android, How to convert video into slow motion and play it in slow motion using FFmpeg

  1er février 2016, par Kishor Ramani

  In Android, How to convert video into slow motion and play it in slow motion using FFmpeg.

  I am using FFmpeg command :

  ffmpeg -i input.mkv -filter:v "setpts=2.0*PTS" output.mkv
  
  
  
  Link : https://trac.ffmpeg.org/wiki/How%20to%20speed%20up%20/%20slow%20down%20a%20video

  but i can’t pass "setpts=2.0*PTS" command with Double Quote in String

      String cmd1 = "-i " + inputpath.mp4 + " " + "-filter:v" + " " 
  
  + "setpts=0.5*PTS"  
  
  + " " +
  
  Environment.getExternalStorageDirectory().getAbsolutePath() + "/hij.mp4";

  if you have any better solution for converting video into slow motion or fast motion then it will be appreciated.

  Thanks.

• FFMpeg Concatenation Filters : Stream specifier ':0' in filtergraph matches no streams

  7 février 2017, par Anthony Eden

  I am developing an application that relies heavily on FFMpeg to perform various transformations on audio files. I am currently testing my FFMpeg configuration on the command line.

  I am trying to concatenate multiple audio files which are in different formats (Primarily MP3, MP2 & WAV). I have been using the official TRAC documentation (https://trac.ffmpeg.org/wiki/How%20to%20concatenate%20(join%2C%20merge)%20media%20files#differentcodec) to help me with this and have created the following command :

  ffmpeg -i OHIn.wav -i OHOut.wav -filter_complex '[0:0] [1:0] concat=n=2:a=1 [a]' -map '[a]' output.wav

  However, when I run this on Mac OS X using version 2.0.1 of FFMpeg, I get the following error message :

  Stream specifier ':0' in filtergraph description [0:0] [1:0] concat=n=2:a=1 [a] matches no streams.

  Here is my full output from the terminal :

  ~/ffmpeg -i OHIn.wav -i OHOut.wav -filter_complex '[0:0] [1:0] concat=n=2:a=1 [a]' -map '[a]' output.wav
  
  
  
  ffmpeg version 2.0.1 Copyright (c) 2000-2013 the FFmpeg developers
  
    built on Aug 15 2013 10:56:46 with llvm-gcc 4.2.1 (LLVM build 2336.11.00)
  
    configuration: --prefix=/Volumes/Ramdisk/sw --enable-gpl --enable-pthreads --enable-version3 --enable-libspeex --enable-libvpx --disable-decoder=libvpx --enable-libmp3lame --enable-libtheora --enable-libvorbis --enable-libx264 --enable-avfilter --enable-libopencore_amrwb --enable-libopencore_amrnb --enable-filters --enable-libgsm --arch=x86_64 --enable-runtime-cpudetect
  
    libavutil      52. 38.100 / 52. 38.100
  
    libavcodec     55. 18.102 / 55. 18.102
  
    libavformat    55. 12.100 / 55. 12.100
  
    libavdevice    55.  3.100 / 55.  3.100
  
    libavfilter     3. 79.101 /  3. 79.101
  
    libswscale      2.  3.100 /  2.  3.100
  
    libswresample   0. 17.102 /  0. 17.102
  
    libpostproc    52.  3.100 / 52.  3.100
  
  Guessed Channel Layout for  Input Stream #0.0 : stereo
  
  Input #0, wav, from 'OHIn.wav':
  
    Duration: 00:00:06.71, bitrate: 1411 kb/s
  
      Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, stereo, s16, 1411 kb/s
  
  Guessed Channel Layout for  Input Stream #1.0 : stereo
  
  Input #1, wav, from 'OHOut.wav':
  
    Duration: 00:00:07.19, bitrate: 1411 kb/s
  
      Stream #1:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, stereo, s16, 1411 kb/s
  
  Stream specifier ':0' in filtergraph description [0:0] [1:0] concat=n=2:a=1 [a] matches no streams.

  I do not understand why this does not work. FFMpeg shows that the streams 0:0 and 1:0 exist in the source files. The only other similar problems online have surrounded the use of the single quote in Windows, however testing of this confirm it does not apply to my Mac command line.

  Any help would be much appreciated.

• Are their technical reasons is MP4 more popular than Webm ?

  1er juin 2019, par dprogramz

  Not looking for opinions. I’m searching for data.

  As it is now, I want to become a webM evangelist. However, I assume there are some actual technical reasons why mp4 is preferred over webm in the bigger picture. I want to know them so I can be accurate in my assessments.

  I’m working on developing a broadcast video messaging graphics engine (think chyron) and using the Chromium engine like OBS does for messaging. So far the results have been excellent.

  One of the best features I’ve found is using webm for video. I should note I am using small (640x480 max) videos as graphics that are on top off a larger full HD video.

  Not only does it seem to have a better compresion:quality ratio than mp4 for my use case, the most important thing is that it has full alpha support, which allows for excellent layering of video objects on top of each other in the HTML DOM, in real time, with no noticable performance hits.

  Aside from it’s predecessor, FLV, I can’t think of another high quality, high compression codec that also supports alpha. I feel like you are stuck using pro-res 4444 or the ancient animation codec to reliable distribute video with an alpha.

  So, that said, are there technical reasons why webM isn’t more adopted than mp4 ?

  I already know the obvious, that there is dedicated hardware to decode mp4. But, is there any technicality that would prevent a hardware webM decoder ? I really want to understand more what the benefits of mp4 are over webM, which i assume is why it is more widely used than webM.

  Thanks !