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• Stream Recorder Using FFmpeg Fails on AWS Lambda

  9 mai, par user30495567

  I am trying to stream audio from URLs and save them to a file in S3 using AWS Lambda with FFmpeg. Here is an example FFmpeg command I'm using :

  


  ffmpeg -hide_banner -loglevel error -t 10 -i http://playerservices.streamtheworld.com/api/livestream-redirect/KTOOFMAAC_SC -ar 16000 -b:a 64k -ac 2 output.mp3


  


  

  • The FFmpeg command is getting called in a python script using subprocess.Popen()

  


  • The command works as expected on local, but does not work in an AWS Lambda python environment using a custom FFMPEG layer configured with these instructions.

  


  • When run on Lambda, I get the following error : FileNotFoundError : [Errno 2] No such file or directory : '/tmp/output.mp3'

  


  


  Note : I've also tried a version where I use python requests to stream chunks and pipe them into ffmpeg. This works for some stream URLs, but for others, such as the streamtheworld URL above, it only saves 5 seconds of audio from the stream or results in a Broken Pipe error.

  


• Architecture of video-based service for mobile phones

  27 juin 2015, par David Azar

  I guess this is more of a conceptual question than a technical one.

  I’m trying to figure out the best way to upload short videos to a server and also be able to download them and watch them on both Android and iOS.

  Lets focus on Android for the moment.

  I’ve done some experiments, and my results have been :

  • I’m able to compress 12-14MB video down to 500KB using FFMPEG lib with pretty good results in quality, but it takes about 12 seconds.

  • Next, im uploading those videos to my Parse backend as ParseFile to store them.

  • Finally, i can download them and watch them with no problem using a VideoView widget.

  Now, for the tests i’ve been running, these are great results. But i want to see if there is a better way to manage and scale all of this.

  My questions are :

  • Is there a better, lighter way to compress video ?

  • Is Parse the right way to go ?

  • How can i stream videos instead of downloading them and storing the on local storage before playing them ? i know this will cause my app to use significant space on disk and i dont want that.

  • How do big companies do this kind of tasks ?

  I’ve heard Amazon S3 is a cool thing for projects like this one, also Google Cloud Platform. I want to understand the best approach before building everything so i can do it the right way and also, provide the absolute best user experience for watching these videos.

• How would I assign multiple MMAP's from single file descriptor ?

  9 juin 2011, par Alex Stevens

  So, for my final year project, I'm using Video4Linux2 to pull YUV420 images from a camera, parse them through to x264 (which uses these images natively), and then send the encoded stream via Live555 to an RTP/RTCP compliant video player on a client over a wireless network. All of this I'm trying to do in real-time, so there'll be a control algorithm, but that's not the scope of this question. All of this - except Live555 - is being written in C. Currently, I'm near the end of encoding the video, but want to improve performance.

  To say the least, I've hit a snag... I'm trying to avoid User Space Pointers for V4L2 and use mmap(). I'm encoding video, but since it's YUV420, I've been malloc'ing new memory to hold the Y', U and V planes in three different variables for x264 to read upon. I would like to keep these variables as pointers to an mmap'ed piece of memory.

  However, the V4L2 device has one single file descriptor for the buffered stream, and I need to split the stream into three mmap'ed variables adhering to the YUV420 standard, like so...

  buffers[n_buffers].y_plane = mmap(NULL, (2 * width * height) / 3,
  
                                      PROT_READ | PROT_WRITE, MAP_SHARED,
  
                                      fd, buf.m.offset);
  
  buffers[n_buffers].u_plane = mmap(NULL, width * height / 6,
  
                                      PROT_READ | PROT_WRITE, MAP_SHARED,
  
                                      fd, buf.m.offset +
  
                                      ((2 * width * height) / 3 + 1) /
  
                                      sysconf(_SC_PAGE_SIZE));
  
  buffers[n_buffers].v_plane = mmap(NULL, width * height / 6,
  
                                      PROT_READ | PROT_WRITE, MAP_SHARED,
  
                                      fd, buf.m.offset +
  
                                      ((2 * width * height) / 3 + 
  
                                      width * height / 6 + 1) / 
  
                                      sysconf(_SC_PAGE_SIZE));

  Where "width" and "height" is the resolution of the video (eg. 640x480).

  From what I understand... MMAP seeks through a file, kind of like this (pseudoish-code) :

  fd = v4l2_open(...);
  
  lseek(fd, buf.m.offset + (2 * width * height) / 3);
  
  read(fd, buffers[n_buffers].u_plane, width * height / 6);

  My code is located in a Launchpad Repo here (for more background) :
  http://bazaar.launchpad.net/ alex-stevens/+junk/spyPanda/files (Revision 11)

  And the YUV420 format can be seen clearly from this Wiki illustration : http://en.wikipedia.org/wiki/File:Yuv420.svg (I essentially want to split up the Y, U, and V bytes into each mmap'ed memory)

  Anyone care to explain a way to mmap three variables to memory from the one file descriptor, or why I went wrong ? Or even hint at a better idea to parse the YUV420 buffer to x264 ? :P

  Cheers ! ^^