python - FFmpeg 将 .mp3 输出保存到变量中

Question

在我的应用程序中，我想修改各种 mp3，然后将它们混合在一起。我知道我可以在 FFmpeg 中使用单个命令行来完成，但它最终会变得非常困惑，因为我需要在每个样本上使用各种过滤器，而我有五个。我的想法是单独编辑每个样本，将它们保存到一个变量中，最后混合它们。这是我的代码:

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)

我的问题是我必须对 stdout 进行编码。我试过 'utf-8' 但出现此错误:

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

使用“utf-16”:

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

为什么要解决这个问题？我的方法正确吗？

感谢@Rotem，我成功地完成了我想做的事情。但现在我面临另一个问题，因为我想混合多达 5 种声音，所以我尝试以懒惰/简单的方式实现它:

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)

令人惊讶的是它有效，我的两个声音在正确的时间开始，但第二个声音搞砸了。所以这不是正确的做法。

然后我按照建议尝试了命名管道:

"pipe1:"

但是我得到这个错误:

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

阅读命名管道 wiki 时指出我必须使用 mkfifo() 创建它们。

所以我尝试了:

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:?

Answer 1

您的方法是正确的，但需要修正。

修复 create_samp():

• 您不需要 "-codec:v", "copy" 参数，因为没有视频流。

修复 record(samp):

• 不能使用"-i" "samp.stdout"，因为samp.stdout是字节数组(Python子进程模块将其用作字符串)。
• 使用 "-i", "pipe:" 从标准输入管道接收第二个音频。
• 因为你想混合两个音频流，你必须使用 "-filter_complex" 参数，和 amix 音频过滤器或 amerge 音频过滤器，如所述here .
• 将samp写入stdin管道，并关闭stdin管道。

---

代码如下:

import subprocess

def create_samp():
    # Read audio stream from https://freesound.org/data/previews/186/186942_2594536-hq.mp3
    # Apply adelay audio filter.
    # Encode the audio in mp3 format.
    # FFmpeg output is passed to stdout pipe, and stored in sample bytes array.
    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 record(samp):
    # Open FFmpeg as sub-process
    # Use two audio input streams:
    # 1. WEB address
    # 2. PIPE (the input is going to be written stdin pipe).
    # Merge the two audio streams using amix audio filter.
    # Store the result to output file: output.mp3
    process = subprocess.Popen(["ffmpeg", "-y", '-f', 'mp3', \
                                "-i", "https://cdns-preview-b.dzcdn.net/stream/c-b0b684fe962f93dc43f1f7ea493683a1-3.mp3", \
                                "-i", "pipe:", \
                                "-filter_complex", "amix=inputs=2:duration=longest", "output.mp3"], stdin=subprocess.PIPE)

    process.stdin.write(samp)  # Write samp (bytes array containing mp3 data).
    process.stdin.close()  # Close stdin pipe.
    process.wait()  # Wait for FFmpeg sub-process to finish

samp = create_samp()
record(samp)

听起来不错...

---

更新:

命名管道实现移至 following发布。