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• FFmpeg save .mp3 output into a variable

  6 mai 2021, par Toto Briac

  In my application I want to modify various mp3 and then mix them together. I know I could do it with a single command line in FFmpeg but It can end up very messy since I need to use various filter on each sample and I have five of them.
My idea is to edit each sample individually, save them into a variable and finally mix them. This is my code :

  


  import subprocess    

def create_samp():
    sample= subprocess.run(["ffmpeg", "-y", "-i", "https://freesound.org/data/previews/186/186942_2594536-hq.mp3", \
                           "-filter_complex", "adelay=15000|15000", "-codec:v", "copy", "-f", "mp3","-"], stdout=subprocess.PIPE)         
    return(sample)    

def record(samp):
    subprocess.run(["ffmpeg", "-y", "-i", "https://cdns-preview-b.dzcdn.net/stream/c-b0b684fe962f93dc43f1f7ea493683a1-3.mp3", \
                    "-i", samp.stdout, "-f", "-mp3", "copy", "output.mp3"])

samp = create_samp()
record(samp)


  


  My issue is that I have to encode the stdout. I've tried 'utf-8' but got this error :

  


  UnicodeDecodeError: 'utf-8' codec can't decode byte 0xff in position 45: invalid start byte


  


  With `'utf-16' :

  


  UnicodeDecodeError: 'utf-16-le' codec can't decode bytes in position 239454-239455: illegal encoding


  


  Why is the way to fix this issue ? Is my approach the right one ?

  


  Thanks to @Rotem I succeed to do what I wanted to. But now I am facing an other issue, since I want to mix up to 5 sounds, I tried to implement it the lazy/easy way :

  


  import subprocess

def create_samp_2():
    sample= subprocess.run(["ffmpeg", "-i", "https://freesound.org/data/previews/186/186942_2594536-hq.mp3", \
                            "-af", "adelay=15000|15000", "-f", "mp3", "pipe:"], stdout=subprocess.PIPE).stdout
    return(sample)

def create_samp():

    sample= subprocess.run(["ffmpeg", "-i", "https://freesound.org/data/previews/370/370934_6399962-lq.ogg", \
                            "-af", "adelay=1000|1000", "-f", "mp3", "pipe:"], stdout=subprocess.PIPE).stdout
    return(sample)


def record(samp, samp_2):        
    process = subprocess.Popen(["ffmpeg", "-y", '-f', 'mp3', \
                                "-i", "https://cdns-preview-b.dzcdn.net/stream/c-b0b684fe962f93dc43f1f7ea493683a1-3.mp3", \
                                "-i", "pipe:", \
                                "-i", "pipe:", \
                                "-filter_complex", "amix=inputs=3:duration=longest", "output.mp3"], stdin=subprocess.PIPE)

    process.stdin.write(samp) 
    process.stdin.write(samp_2)        
    process.stdin.close()  
    process.wait()

samp = create_samp()
samp_2 = create_samp_2()
record(samp, samp_2)


  


  Surprisingly it works, my two sounds start at the right time, but the second sound is messed up. So it's not the right way to do it.

  


  Then I tried named pipes as suggested this way :

  


  "pipe1:"


  


  But I get this error :

  


  pipe1:: Protocol not found
Did you mean file:pipe1:?


  


  Reading named pipe wiki it is stated that I have to create them with mkfifo().

  


  So I tried :

  


  import os
pipe1 = "pipe1"

def create_pipe1():
    os.mkfifo(pipe1)

But now I have this error: pipe1:: Protocol not found
Did you mean file:pipe1:?


  


• How to translate bgr data to CVPixelBufferRef ?or how to play just bgr data in iOS

  4 décembre 2016, par warlock

  I have got some RGB data used live555 & FFmpeg, but how can I play it as a video ?

  I Google a lot and found that avplayer maybe help. Others I searched link me to UIImage translate to rgb...or your search returned no matches.

  This is one I searched, but it is "Create ", not "Play ".

  possible to create a video file from RGB frames using AV Foundation

  I try to use AVsampleBufferDisplayLayer, but I don’t know how to translate.

  Anyone can help ?

• vp9/x86 : save one register on 32bit idct32x32.

  16 décembre 2014, par Ronald S. Bultje

  vp9/x86 : save one register on 32bit idct32x32.
  Fixes build on win32.
  Signed-off-by : Michael Niedermayer <michaelni@gmx.at>
  

  • [DH] libavcodec/x86/vp9itxfm.asm