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• Real time compression/encoding using ffmpeg in objective c

  20 février 2014, par halfwaythru

  I have a small application written in Objective-c that looks for the video devices on the machine and allows the user to record video. I need to be able to compress this video stream in real time. I do not want to save the whole video, I want to compress it as much as possible and only write out the compressed version.

  I also don't want to use the AVFoundation's build in compression methods and need to use a third party library like ffmpeg.

  So far, I have been able to record the video and get individual frames using 'AVCaptureVideoDataOutputSampleBufferDelegate' in this method :

  - (void)captureOutput:(AVCaptureOutput *)captureOutput
  
     didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer
  
     fromConnection:(AVCaptureConnection *)connection

  So I have a stream of images basically, and I want to throw them into ffmpeg (which is all set up on my machine). Do I need to call a terminal command to do this ? And if I do, how do I use the image stack as my input to the ffmpeg command, instead of the video. Also, how do I combine all the little videos in the end ?

  Any help is appreciated. Thanks !

• FFmpeg : Pipe segments to s3

  24 septembre 2024, par Brendan Kennedy

  I'd like to pipe ffmpeg segments to s3 without writing them to disk.

  


  ffmpeg -i t2.mp4 -map 0 -c copy -f segment -segment_time 20 output_%04d.mkv


  


  Is it possible to modify this command so that ffmpeg writes segments to an s3 bucket ? Something like this perhaps ?

  


  ffmpeg -i t2.mp4 -map 0 -c copy -f segment -segment_time 20 pipe:1 \
  | aws s3 cp - s3://bucket/output_%04d.mkv


  


  When I run the command above I receive this error

  


  Could not write header for output file #0
(incorrect codec parameters ?): Muxer not found


  


  This command works except the entire video is uploaded and not the individual segments

  


  ffmpeg -i t2.mp4 -map 0 -c copy -f segment -segment_time 20 pipe:output_%04d.mkv \
| aws s3 cp - s3://bucket/test.mkv


  


• speeding up x264 encoding (C++ code with libavcodec)

  20 décembre 2012, par Hrishikesh_Pardeshi

  I am trying to capture windows screen (continuous screen shots) and encode them into x264. For that I am using avcodec_encode_video2 function available with libavcodec. However, it takes a huge amount of time. The time fluctuates between 25 – 1800 milliseconds for encoding individual frames.

  I tried tried both 1080p and 720p with video recording on screen.

  These are the settings I am using. This was tested on Windows 7, win32 release build with 4 GB of RAM.

  bit_rate = 2000, width = 1920, height = 1080
  qmin = 0, qmax = 0, max_b_frames = 0, frame_rate = 25, pixel_format = YUV 4:4:4.
  The remaining settings are default which are fetched using avcodec_get_context_defaults3().

  Sample data(in milliseconds) for 20 frames (consecutive and chosen randomly) in a set of 250 frames.
  121, 106, 289, 126, 211, 30, 181, 58, 213, 34, 245, 50, 56, 364, 247, 171, 254, 83, 82, 229

  For the application it is a must that it captures at least at 15 fps. Can someone help out to tell whether any options can be used to improve the frame rate. I need to encode lossless, but I am open to some file size increase.

  Thanks in advance.