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• Windows Ffmpeg - send audio to sound card's output

  30 mars 2021, par halitsafa

  I have a sound card (Behringer UMC202HD) which connected to a Windows 10 computer by usb cable, i am able to recieve audio from input device with the following ffmpeg command :
ffmpeg -f dshow -i audio="IN 1-2 (BEHRINGER UMC 202HD 192k)" -map_channel 0.0.0 -c:a pcm_s24le first_channel.wav -map_channel 0.0.1 -c:a pcm_s24le second_channel.wav

  


  But i can't send audio to sound card's output with the ffmpeg, is there any way to do this ? if there is, how can i do it ?

  


  Linux version (pseudo command) of what i'm trying to do in Windows :

  


  ffmpeg -i my_input.wav -f alsa alsa.behringer_out

  


• Java IO Streaming Large Files Video/Data/Sound [on hold]

  2 mars 2015, par James Relic

  I have a series of questions listed below regarding java.io streaming and sockets.

  1. What is a video streaming server ? How does it differ from a standard web server.

  2. Remember Napster/Morpheus etc ? They’re P2P programs, did they allow users to stream data to each other ? Is there a difference between streaming and downloading (on the clients end) ?

  3. How would you go about writing a generic program in java that streams anything to the client , word docs, mp3 files, videos files ? Would you use serverlets for this purpose ?

  4. If all you are doing is sending files video/sound/docs/text etc from one computer to another would you need to use specialist APIs like FFMPEG-Java, Red5 ?

  5. if you are sending video or sound as a file supposedly you don’t need to worry about encoding or decoding ?

  6. Do I need to worry about RTSP if im streaming videos as a file ? Rather then wanting them to play live on the client end ?

  I understand my questions sound very untechnical and basic, but I’m a little confused on this whole streaming topic and want to know the best way to stream large files of all types using the Java EE/Spring platform.

• I would like to batch-trim mp4 videos in a folder with command line (ffmpeg ?), however the sound is delayed

  28 janvier 2023, par pdeli

  I found the following command line to batch-trim videos in a folder, however it delays the sound of all the videos by a few seconds (sound comes after the video) :

  


  for file in /path/to/folder/*.mp4; do ffmpeg -i "$file" -ss 00:00:08 -c copy -avoid_negative_ts 1 "${file%.*}_trimmed.mp4"; done

  


  These are the alternatives I found, however none of them solve the problem :

  


  for file in /path/to/folder/*.mp4; do ffmpeg -i "$file" -itsoffset -0.5 -ss 8 -c:v copy -c:a copy "${file%.*}_trimmed.mp4"; done

  


  for file in /path/to/folder/*.mp4; do ffmpeg -i "$file" -ss 8 -async 1 -c:v copy -c:a copy "${file%.*}_trimmed.mp4"; done

  


  for file in /path/to/folder/*.mp4; do ffmpeg -i "$file" -ss 8 -map 0:v -map 0:a -c:v copy -c:a copy "${file%.*}_trimmed.mp4"; done

  


  I have a hard time finding by how much time the sound is delayed.

  


  My questions :

  


  

  • what would be the command line to batch-trim the beginning of all the videos in a folder with the sound properly "aligned" to the video ?

  


  • in other words, can't the sound be by default trimmed by as much as the video in the first place ? If yes, how ?

  


  


  ---

  


  System used :

  


  

  • macOS Ventura (13.1, Intel)

  


  • Shell and version : zsh 5.8.1 (x86_64-apple-darwin22.0)

  


  • ffmpeg version 5.0 built with Apple clang version 13.0.0 (clang-1300.0.29.30)