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• convert WAV to TETRA format

  14 juin 2020, par Ashish Arora

  I am trying to convert a wav file into TETRA encoded file (https://en.wikipedia.org/wiki/Terrestrial_Trunked_Radio). Tetra is used by fire-fighters, it provides a radio-like voice.

  



  I am trying to use the official tetra codec codes available at (https://www.etsi.org/deliver/etsi_en/300300_300399/30039502/01.03.01_60/) and we can easily compile it using the scripts available at https://github.com/sq5bpf/install-tetra-codec.

  



  However, I am not able to figure out how to convert a wav file into tetra codec files using these files. I tried going through the documentation of the compiled files (ccoder, cdecoder, scoder, sdecoder).

  



  I tried the following command -

  



  


  tetra/bin/scoder input.wav serial_file synth_file

  


  



  here serial_file and synth_file are the output files and have following documentation in the scoder.c file :

  



      INPUT   :   - Description : speech file to be analyzed
                - Format : binary file 16 bit-samples
                  240 samples per frame

serial_file :   - Description : serial stream output file 
            - Format : binary file 16 bit-samples
              each 16 bit-sample represents one encoded bit
              138 (= 1 + 137) bits per frame

synth_file  :   - Description : local synthesis output file 
            - Format : binary file 16 bit-samples


  



  For an input file of size 13M, I obtained serial_file and synth_file of size 8.0M and 16M. However, I thought since the wav file is getting converted into a walkie-talkie type signal the output file size will be alot smaller.

  



  I want to clarify if :

  



  

  • I used the correct code to convert an input wav file into a tetra format output file.

  


  • can you please help me understand, what is serial_file and synth_file.

  


  



  Thanks,
Ashish

  


• mencoder. Encoding from multiple input image files compatible with web browser (No video support and MIME type) [duplicate]

  23 juin 2020, par iblasi

  I have multiple JPG files that I want to use to make a TimeLapse video compatible with the web browser to upload it on my web page.
Create a video with mencoder from multiple images is explained in some webpages such us here, that shows how to create a video.

  


  ls -Ltr my_Pics/*.jpg >files.txt
mencoder -nosound -ovc lavc -lavcopts vcodec=mpeg4 -o video.avi -mf type=jpeg:fps=4 mf://@files.txt


  


  The video is set with no sound and to have one picture every 250ms (4 fps).
These command lines create an AVI video that I can see correctly with the VLC video tool. However, if I try to open it in a web browser it shows an error :

  


  


  No Video with Supported Format and MIME type found

  


  


  So, based on other similar comments (as here), I tryed to use ffmpeg renaming all my files as ffmpeg requires a number serial format. But it happens the same, that I can see it in VLC but not in the browser.

  


  ffmpeg -r 4 -i ./output/%04d.jpg -vcodec libx264 video.mp4


  


  Based on research made on internet I am quite sure that it is due the the encoding and/or container. I tryed multiple options of codecs nd containers existing on documentation (here) but still not able to find a way to work.

  


  If, once I create the video, I use the VLC tool to manually convert the video to ".m4v" I was able to create a video that the web browser recognizes. But I would like to do it with command lines to automate it.

  


• How to access builtin webcam from a docker container using ffmpeg ?

  1er novembre 2020, par philippos

  I have wrote my code that captures videos by my builtin webcam of my MAC using ffmpeg.

  On local machine, the code works fine. However, I built a docker container of my code, and tried to run it, but I got the following error :

  


  error: Command failed: ffmpeg -f avfoundation -framerate 30 -i "0" -target pal-vcd -vf scale=640x480 -flags +global_header -f segment -segment_time 10 -segment_list ../out.csv -segment_format_options movflags=+faststart -reset_timestamps 1 -strftime 1 %Y%m%d-%H%M%S.mp4
ffmpeg version git-2016-05-25-9591ca7 Copyright (c) 2000-2016 the FFmpeg developers
  built with gcc 4.8 (Ubuntu 4.8.4-2ubuntu1~14.04.3)
  configuration: --extra-libs=-ldl --enable-gpl --enable-libass --enable-libfdk-aac --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libmp3lame --enable-libopus --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-nonfree --enable-openssl
  libavutil      55. 24.100 / 55. 24.100
  libavcodec     57. 43.100 / 57. 43.100
  libavformat    57. 37.100 / 57. 37.100
  libavdevice    57.  0.101 / 57.  0.101
  libavfilter     6. 46.100 /  6. 46.100
  libswscale      4.  1.100 /  4.  1.100
  libswresample   2.  0.101 /  2.  0.101
  libpostproc    54.  0.100 / 54.  0.100
Unknown input format: 'avfoundation'


  


  

  1. as far as what I understood from this log, is that the docker
container doesn't have access to local devices.
     According to
this discussion Docker - a way to give access to a host USB or
serial device ? , I need to use the --device flag to pass my
device's location.
     However, according to this answer,
that is not possible ?

  


  2. In addition to what I've mentioned
above, I couldn't get my webcam's path at the first place. what is
a correct path for macbook webcam

  


  


  My question is : How to access my MAC's builtin camera to record from a docker container ?