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• ffplay won't with with more than 6 audio channels

  13 juin 2020, par Hiko Haieto

  I am trying to stream (raw) video and audio from a capture device as part of my home media setup (with my pc acting similarly to a receiver in a typical home theatre setup), but the biggest problem I haven't been able to get past is that I haven't been able to get ffplay to work with all 8 channels in 7.1 streams - two simply get dropped, despite it recognising 8 channel input or me specifying a 7.1 layout.

  



  I have been able to confirm that all 8 channels are present in the source by first using ffmpeg to save the output of a speaker test to a file and playing that back with both mplayer (which works) and ffplay (which doesn't). I might simply use mplayer if it weren't for the fact that piping output from ffmpeg adds too much latency for real-time use. I am using libSDL version 2.0.12 and ffplay 4.2.3, both of which are the latest at the time of writing and are ostensibly supposed to support 7.1 audio.

  



  Using output recorded from speaker-test -c 8, I am using the following to play it back in mplayer :

  



  mplayer -channels 8 -rawaudio channels=8 -format s16le -demuxer rawaudio speaker-test.pcm


  



  and the following to play it back in ffplay :

  



  ffplay -f s16le -ac 8 -af 'channelmap=channel_layout=7.1' speaker-test.pcm


  



  No matter what I try, ffplay is dropping the two side channels. Why might ffplay not be producing output for all 8 channels, and how might I fix it ?

  


• Ffmpeg gentle stop sending [closed]

  31 mars 2023, par Ли Шеньшунь

  Good day. I'm trying to do a simple video sending and receiving on two computers that are on the same network. Video simulates streaming (video conference for example). I want to use ffmpeg but have run into a number of difficulties.
I start with two simple scripts :
Sender machine

  


  ffmpeg -re -i input_file.mp4 -c copy -f mpegts udp://192.168.2.10:1234


  


  recipient machine :

  


  ffmpeg -i udp://192.168.2.10:1234 -c copy save_video.mp4


  


  I got 2 questions :

  


  

  1. Is there a way to correctly end video reception when the sender does not send anything else ?

  


  


  The receive command works by waiting indefinitely. If the sender is still sending video and at this moment interrupt the receiver with ctrl+c, then the video is saved correctly. If the sender is finished, then after that, to stop, you need to use ctrl + c twice and the video is "broken", because. does not open apparently due to damage to the meta-data or codecs.

  


  I'm aware of options like using timeout, or saving to mkv format, they really work. But setting a specific number of seconds is problematic, and simply killing a process does not look very nice.

  


  

  2. Is the -re switch enough to simulate a "webcam" from a video file ? I heard that ffmpeg buffers packets in case of loss and can send them later later. I need to send it as it is, if there are any problems, then we lose the package forever. The -flush_packets key, as I understand it, is for writing to a file, but not when sending over the network.

  


  


• ffmpeg : remove misleading and incorrect warning messages

  15 juin 2017, par wm4

  ffmpeg : remove misleading and incorrect warning messages
  It is wrong/incorrect in two aspects :
  
  1. The pixel format is not enough to guarantee that the resulting file
  
     will be any more compatible with media players.
  
  2. Media players not supporting higher profiles are not necessarily
  
     outdated (in fact this is simply an arrogant statement that
  
     libavcodec can handle these particular features).
  You could add that there are plenty of other ways to produce widely
  
  incompatible files with ffmpeg, and these don't show any warnings.
  What we really want to do here is defaulting to codec profiles that
  
  have wide compatibility, such as main/high for h264. Also, if an
  
  encoder does not accept certain pixfmts, we should automatically
  
  convert them to a pixfmt the encoder can accept. But the existing
  
  message certainly is not appropriate.
  It also works for 2 specific encoders only. Extending it for other
  
  cases would result in a lot of special cases, so this is not the
  
  right place.
  

  • [DH] ffmpeg.c