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• Android Live Streaming based on javaCV + FFMpeg crashes by adding red5 link

  1er octobre 2015, par user1914692

  The Android application code is from :
  Android Live Streaming courtesy of JavaCV and FFMPEG

  It streams the live camera video from the device.

  I follow one comment’s instruction (Yoshio Numai), to use Red5 as the stream server.
  By Red5 itself, I can successfully use simpleBroadcaster and simpleSubscriber to stream and display the live camera (from the computer) steam.

  In the MainActivity.java, I change the code as below :

  private String ffmpeg_link = "rtmp://192.168.1.105/oflaDemo/red5StreamDemo"; 

  And I can start the app in my Android device (Nexus 4).
  after click "start", the app crash, pops out a small window, saying :
  "Unfortunately, JavaCV 0.3 Stream Test has stopped. OK."

  Once I click the OK button, I find the app is still live in the task list.

  But the same thing will happen.
  What’s wrong here ?

• Android MediaRecorder setCaptureRate() and video playback speed

  7 novembre 2013, par spitzanator

  I've got a MediaRecorder recording video, and I'm very confused by the effect of setCaptureRate().

  Specifically, I prepare my MediaRecorder as follows :

  mMediaRecorder = new MediaRecorder();
  
  mCamera.stopPreview();
  
  mCamera.unlock();
  
  mMediaRecorder.setCamera(mCamera);
  
  mMediaRecorder.setVideoSource(MediaRecorder.VideoSource.CAMERA);
  
  mMediaRecorder.setProfile(CamcorderProfile.QUALITY_TIME_LAPSE_480P);
  
  mMediaRecorder.setCaptureRate(30f);
  
  mMediaRecorder.setOrientationHint(270);
  
  mMediaRecorder.setOutputFile(...);
  
  mMediaRecorder.setPreviewDisplay(...);
  
  mMediaRecorder.prepare();

  I record for five seconds (with a CountDownTimer, but that's irrelevant), and this is the file that gets generated :

  $ ffmpeg -i ~/CaptureRate30fps.mp4 
  
  ...
  
  Seems stream 0 codec frame rate differs from container frame rate: 180000.00 (180000/1) -> 30.00 (30/1)
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/home/mspitz/CaptureRate30fps.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 0
  
      compatible_brands: isom3gp4
  
      creation_time   : 2013-06-04 00:52:00
  
    Duration: 00:00:02.59, start: 0.000000, bitrate: 5238 kb/s
  
      Stream #0.0(eng): Video: h264 (Baseline), yuv420p, 720x480, 5235 kb/s, PAR 65536:65536 DAR 3:2, 30 fps, 30 tbr, 90k tbn, 180k tbc
  
      Metadata:
  
        creation_time   : 2013-06-04 00:52:00

  Note that the Duration is just about 3 seconds. The video also plays much faster, as if it were 5 seconds of video crammed into 3.

  Now, if I record by preparing my mediaRecorder exactly as above, but subtracting the setCaptureRate(30f) line, I get a file like this :

  $ ffmpeg -i ~/NoSetCaptureRate.mp4 
  
  ...
  
  Seems stream 0 codec frame rate differs from container frame rate: 180000.00 (180000/1) -> 90000.00 (180000/2)
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/home/mspitz/NoSetCaptureRate.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 0
  
      compatible_brands: isom3gp4
  
      creation_time   : 2013-06-04 00:50:41
  
    Duration: 00:00:04.87, start: 0.000000, bitrate: 2803 kb/s
  
      Stream #0.0(eng): Video: h264 (Baseline), yuv420p, 720x480, 2801 kb/s, PAR 65536:65536 DAR 3:2, 16.01 fps, 90k tbr, 90k tbn, 180k tbc
  
      Metadata:
  
        creation_time   : 2013-06-04 00:50:41

  Note that the Duration is as expected, about 5 seconds. The video also plays at a normal speed.

  I'm using setCaptureRate(30f) because 30 frames per second is the value of my CamcorderProfile's videoFrameRate. On my Galaxy Nexus S2 (4.2.1), omitting setCaptureRate() is fine, but when I tested on a Galaxy Nexus S3 (4.1.1), omitting setCaptureRate() results in the ever-helpful "start failed -22" error when I called mMediaRecorder.start().

  So, what am I missing ? I thought that the capture rate and the video frame rate were independent, but it's clear that they're not. Is there a way to determine programmatically what I need to set the capture rate at in order to determine that my video plays back at 1x speed ?

• Input seeking for frame at specified timestamp with Py-AV

  9 décembre 2019, par neonScarecrow

  I have a project already using Py-AV and am trying to replicate a specific ffmpeg command. The goal is to get a frame roughly around the specified timestamp.

  Here’s the ffmpeg commmand :
  https://trac.ffmpeg.org/wiki/Seeking

  ffmpeg -ss 14 -i https://some_url.mp4 -frames:v 1 frame_at_14_seconds.jpg

  Here’s my code :

      #return one frame around 14 seconds into the movie
  
      target_sec = 14 
  
      container = av.open('https://some_url.mp4', 'r')
  
      container.streams.video[0].thread_type = 'AUTO'
  
      video_stream = next(s for s in container.streams if s.type == 'video')
  
      time_base = float(video_stream.time_base)
  
      target_timestamp = int(target_sec / time_base) + video_stream.start_time
  
      video_stream.seek(target_timestamp)
  
      for frame in container.decode(video_stream):
  
          frame.to_image().save('frame_at_14_seconds.jpg')
  
          break

  Additionally, I have found any documentation about this, but does anyone know if either command (ffmpeg/av.open) is downloading the entire file to a tmp file behind the scenes. I’m looking for a less memory-intensive way to read a frame for every second in an up to 60 second video.