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• Convert wmv to mp4 with ffmpeg failing

  10 janvier 2012, par Morph

  I've seen quite a few posts on this, but I can't piece together whether I am doing things right, wrong, or need to download more stuff. I am converting from wmv to mp4 without complaints, but then when I go to play it on the browser window (HTML5) the player just turns grey and blanks out the controls.

  Installing ffmpeg I do

  ./configure --disable-yasm ; make ; make install

  Unless I include the disable yasm it wont go any further. Then I do

  ffmpeg -i myvideo.wmv myvideo.mp4

  All good so far. In my html source I have :

    <video width="320" height="240" controls="controls">
  
    <source src="myvideo.mp4" type="&#39;video/mp4;" codecs="avc1.42E01E, mp4a.40.2"></source>
  
    Your browser does not support the video tag.
  
    </video>

  I am playing this in Chrome 15 and ffmpeg -v is

  ffmpeg version 0.8.6, Copyright (c) 2000-2011 the FFmpeg developers
  
  built on Dec  1 2011 15:42:06 with gcc 4.1.2 20080704 (Red Hat 4.1.2-51)
  
  configuration: --disable-yasm
  
  libavutil    51.  9. 1 / 51.  9. 1
  
  libavcodec   53.  7. 0 / 53.  7. 0
  
  libavformat  53.  4. 0 / 53.  4. 0
  
  libavdevice  53.  1. 1 / 53.  1. 1
  
  libavfilter   2. 23. 0 /  2. 23. 0
  
  libswscale    2.  0. 0 /  2.  0. 0

  So I get the HTML5, click on it to play the movie but then the control bar greys out, leaving the play button, but then the play button cannot be clicked and nothing plays.

  Is there something wrong with what I have done above ? Do I need to download some separate mp4 driver and compile it ? I see people referring to h.264 but I thoughts ffmpeg had that already included...

• Using GDIgrab in FFmpeg with dshow Audio produces black screen

  16 mars 2016, par Spreadys

  here is my command :

  ffmpeg -f gdigrab -framerate 25 -offset_x 10 -offset_y 10 -show_region 1 -draw_mouse 1 -video_size 1280x720 -i desktop -f dshow -i audio="Microphone (2- ATR USB microphone)" -r 25 -threads 4 -c:v libx264 -pix_fmt yuv422p -preset superfast -tune fastdecode -x264opts keyint=25:min-keyint=1 -crf 4 -c:a aac -profile:a aac_low -async 25 "C:\Users\david\Desktop\%output%.mp4"

  The gdigrab video works great when it is on its own (no audio). The audio works fine when it is on its own (no video). When I join the two commands to capture both together, as soon as I move a window within my capture area, the area goes black.

  In Windows 7, I used to get around this by stopping the desktop composition service prior to capture, (SC stop uxsms), but this is now not possible in Win10.

  I thought it may be something graphics card related.
  My main monitor is on an Nvidia card, with my second running from the onboard Intel. This is setup for Quicksync H264 playback and encoding with my NLE.

  I know that I could use a dshow screen capture driver such as UScreen but am trying to avoid that as I need the capture area to be specified each time from a simple batch.

  Any help appreciated to solve this black area problem- its driving me crazy !
  David

• How do I play back video on Android with custom playback speed ?

  13 novembre 2015, par guidow

  I want to play back a video in Android, rendering it to a SurfaceTexture or something else that is usable as an OpenGL ES texture, but I need very precise control over the playback speed of the video to synchronize it to a stream of external events. These events will happen at a roughly predictable speed, but the exact speed will depend on many small mechanical details, influenced by many small factors, including the weather (and possibly even the phase of the moon...).

  The android.media.MediaPlayer class provided by android allows rendering to a SurfaceTexture (and the 360Videos app from the Oculus Mobile SDK successfully uses that feature), but unfortunately does not seem to allow altering the playback speed, at least not as far as I could tell from the documentation here.

  I have tried pausing and resuming the playback using pause() and start() respectively, to influence the playback speed, but that leads to extremely choppy and slow playback. My idea here was to make the video have a higher framerate than would ever be needed, and to then manually retard every frame until it actually needs to be shown. From the messages in the log, it looks to me like the MediaPlayer class will release various needed resources on pause and rerequest them on resume, which obviously kills performance if you do that once per frame.

  Another option I am looking at is ffmpeg. This one seems like it will do what i want, it doesn’t do any timings itself, it just decodes frames whenever I tell it to to a buffer, leaving me to use it however I want, whenever I want. The obvious drawback is that ffmpeg, at least on android, doesn’t do hardware decoding and probably won’t be able to decode 4K media in realtime.

  Yet another thing I was looking at was OpenMAX AL. Unfortunately, OpenMax AL is pretty hard to get into. I haven’t found any good beginner’s documentation yet, only some old, maybe outdated, READMEs as well as the interface specification from Khronos. The latter is a very long and cumbersome read, though, and I couldn’t yet even figure out if OpenMAX AL will even allow me to do my own timings...