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• Get frame from live video stream

  10 avril 2013, par rickster

  I am streaming live video from my camera on my android phone to my computer using the MediaRecorder class.

  recorder.setCamera(mCamera);
  
  recorder.setVideoSource(MediaRecorder.VideoSource.CAMERA);
  
  recorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);          
  
  recorder.setOutputFile(uav_UDP_Client.pfd.getFileDescriptor());                     
  
  recorder.setVideoEncoder(MediaRecorder.VideoEncoder.H264);

  That's the basic idea. So I would like to show this stream in real time. My plan is to use FFMpeg to turn the latest frame into a .bmp and show the .bmp on my C# program every time there is a new frame.

  The problem is there is no header until I stop the recording. So I can not use FFMpeg unless there is a header. I've looked at spydroid and using RTP but I do not want to use this method for various reasons.

  Any ideas on how I can do this easily ?

• Why frame->pts increases by 20, rather than by 1 ?

  19 mars 2013, par user1914692

  Following the exmaples of ffmpeg : decoding_encoding.c and filtering_video.c, I process one video file taken by iPhone. The video file : .mov, video dimensions ; 480x272, video Codec : H.264/AVC, 30 frames per second, bitrate : 605 kbps.

  I first extract each frame, which is YUV.
  I convert YUV to RGB24, and process the RGB24, then write the RGB24 to a .ppm file. It shows the .ppm file is correct.

  Then I plan to encode processed RGB24 frames to a video file.
  Since MPEG does not support RGB24 picture format, I used AV_CODEC_ID_HUFFYUV.
  But the output video file (showing 18.5 MB) does not play. Movie Player on Ubuntu claims an error : Could not determine type of stream.
  I also tried it on VCL. It simply does not work, without any error information.

  My second questions is :
  For each extracted fram from the input video file, I get its pts as follows according to filtering_video.c :

  frame->pts = av_frame_get_best_effort_timestamp(frame);

  I print out each frame's pts, and find that it increases by 20, like below :

  pFrameRGB_count: 0,  frame->pts: 0
  
  pFrameRGB_count: 1,  frame->pts: 20
  
  pFrameRGB_count: 2,  frame->pts: 40
  
  pFrameRGB_count: 3,  frame->pts: 60

  Where frame is the extracted frame from the input video, and pFrameRGB_count is the count for processed frame in RGB24 form.

  Why are they wrong ?

• ffmpeg Live Input MP4 Error [migrated]

  3 mars 2013, par Brianjs

  Currently I have a mic and a webcam connected to my computer. I am running ffmpeg on CentOS 6.3.

  When I try to record a video without audio by :

  ffmpeg -y -f video4linux2 -t 15 -s 640x480 -r 25 -i /dev/video0 /home/irdb/Desktop/out2.mp4

  it runs perfectly and I get a nice video. However when I try to run with audio included by :

  ffmpeg -y -f video4linux2 -t 15 -s 640x480 -r 25 -i /dev/video0 -f alsa -ar 22050 -ab 64k -ac 2 -i default /home/irdb/Desktop/out2.mp4

  It errors out and prints :

  [NULL @ 0x1e33fc0] Codec is experimental but experimental codecs are not enabled,      see -strict -2
  
  Output #0, mp4, to '/home/irdb/Desktop/out2.mp4':
  
  Stream #0:0: Video: h264, yuv420p, 640x480, q=-1--1, 90k tbn, 25 tbc
  
  Stream #0:1: Audio: none, 22050 Hz, 2 channels, flt, 128 kb/s
  
  Stream mapping:
  
  Stream #0:0 -> #0:0 (rawvideo -> libx264)
  
  Stream #1:0 -> #0:1 (pcm_s16le -> aac)
  
  Error while opening encoder for output stream #0:1 - maybe incorrect parameters such    as bit_rate, rate, width or height

  I assume this has to do with the first error as when I use something like mpg it works just fine. However I plan on streaming this live and want mp4 format as that is pretty much supported by all browsers (Firefox with flash fallback).

  Does anyone know how to get the audio to work without additional processing (as I want to stream live and not write to a file eventually).