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• How can I synchronize a method call with alsa playback ?

  23 novembre 2015, par modwizcode

  I’m trying to write a program that will synchronize lights to playback of a basic wav file. I’ve struggled through all the alsa docs, the source for ffplay.c and searched around on the internet, but it’s difficult to figure out how to do what seems like a common and simple task.

  Basically I want to do two things, the first is to read keypress events while the audio is playing and store the offsets in a file. The second is take those queue files and load them later, this time on a different audio device like a raspberry pi.

  I’m struggling with how to first account for the latency in the initial capture of the offset positions and then how to handle that latency when I playback on a completely different hardware device.

  I know snd_pcm_delay() is used by the ffmpeg suite to deal with some of this, but I’m really struggling with even the basic technique. It’s not a complicated playback mechanism, just a blocking write in a loop.

  I’d post some code, but I don’t have it with me at the moment and it’s just a mess of the current hacks that aren’t working.

• Why is FFMPEG not using hardware decoding on Android when using the h264_mediacodec decoder ?

  28 avril 2021, par helloman

  I'm trying to use FFMPEG in C++ using the h264_mediacodec decoder to decode a video on Android. The frame I receive is AV_PIX_FMT_NV12 instead of AV_PIX_FMT_MEDIACODEC, which implies that the hardware decoding isn't working.

  


  I followed this example to set up the decoder. I tried it on Windows with h264_cuvid and it works as expected, but on Android using mediacodec, I can't get the frame in the expected format.

  


• Trying to use the arcade library on Python3 with Debian 10 errors with pyglet_ffmpeg

  30 mars 2020, par Colin

  I’ve been trying to use the arcade library this morning with python3 but keep getting nothing but errors.

  My environment is Debian 10 (buster)

  I checked first to ensure I have python 3 installed, this confirmed as Python 3.7.3

  I double checked (according to the arcade library website arcade linux installation instructions and ran the install for python3 to make sure that pip and the required libraries were installed.

  I then ran the command to install the library

  sudo pip3 install arcade

  And to test it, copied and pasted the happy_face.py example. However when I tried to run it I got a slew of errors. This seems to be directly related to the arcade installation and if I just run a python script (test.py) with just one line

  import arcade

  At the terminal with

  python3 test.py

  I get the following errors

  Unable to find match for ffmpeg sound library at expected location :
  /usr/local/lib64/python3.7/dist-packages/pyglet_ffmpeg2/linux_x86_64/libavcodec.so.58.*

  Unable to find match for ffmpeg sound library at expected location :
  /usr/local/lib64/python3.7/dist-packages/pyglet_ffmpeg2/linux_x86_64/libavformat.so.58.*

  Unable to find match for ffmpeg sound library at expected location :
  /usr/local/lib64/python3.7/dist-packages/pyglet_ffmpeg2/linux_x86_64/libswresample.so.3.*

  Unable to find match for ffmpeg sound library at expected location :
  /usr/local/lib64/python3.7/dist-packages/pyglet_ffmpeg2/linux_x86_64/libavfilter.so.7.*

  Unable to find match for ffmpeg sound library at expected location :
  /usr/local/lib64/python3.7/dist-packages/pyglet_ffmpeg2/linux_x86_64/libavutil.so.56.*

  Unable to find match for ffmpeg sound library at expected location :
  /usr/local/lib64/python3.7/dist-packages/pyglet_ffmpeg2/linux_x86_64/libswscale.so.5.*

  Unable to find match for ffmpeg sound library at expected location :
  /usr/local/lib64/python3.7/dist-packages/pyglet_ffmpeg2/linux_x86_64/libavcodec.so.58.*

  Unable to find match for ffmpeg sound library at expected location :
  /usr/local/lib64/python3.7/dist-packages/pyglet_ffmpeg2/linux_x86_64/libavformat.so.58.*

  Unable to find match for ffmpeg sound library at expected location :
  /usr/local/lib64/python3.7/dist-packages/pyglet_ffmpeg2/linux_x86_64/libswresample.so.3.*

  Unable to find match for ffmpeg sound library at expected location :
  /usr/local/lib64/python3.7/dist-packages/pyglet_ffmpeg2/linux_x86_64/libavfilter.so.7.*

  Unable to find match for ffmpeg sound library at expected location :
  /usr/local/lib64/python3.7/dist-packages/pyglet_ffmpeg2/linux_x86_64/libavutil.so.56.*

  Unable to find match for ffmpeg sound library at expected location :
  /usr/local/lib64/python3.7/dist-packages/pyglet_ffmpeg2/linux_x86_64/libswscale.so.5.*

  I have used the following terminal command to identify the version of OpenGL installed

  glxinfo | grep "OpenGL version"

  Which returned

  OpenGL version string : 3.3 (Compatibility Profile) Mesa 18.3.6

  I have also tried the terminal command

  sudo pip3 install pyglet-ffmpeg

  Which returns

  Requirement already satisfied : pyglet-ffmpeg in
  /usr/local/lib/python3.7/dist-packages (0.1.4)

  Requirement already satisfied : pyglet>=1.4.0a1 in
  /usr/local/lib/python3.7/dist-packages (from pyglet-ffmpeg) (1.5.0)

  Requirement already satisfied : future in
  /usr/local/lib/python3.7/dist-packages (from
  pyglet>=1.4.0a1->pyglet-ffmpeg) (0.18.2)

  Any assistance would be appreciated. I’ve tried to be as concise as I can, but if more information is required, I’ll gladly supply it.