ffmpeg 中的多个命名管道 [英] Multiple named pipes in ffmpeg
问题描述
这个问题是这个问题的后续
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，但它最终可能会非常混乱，因为我需要对每个样本使用各种过滤器，而且我有五个.我的想法是单独编辑每个样本，将它们保存到管道中，最后将它们混合.
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 pipe and finally mix them.
import subprocess
import os
def create_pipes():
os.mkfifo("pipe1")
os.mkfifo("pipe2")
def create_samp():
sample= subprocess.run(["ffmpeg", "-i", "https://freesound.org/data/previews/186/186942_2594536-hq.mp3", \
"-af", "adelay=15000|15000", "-f", "mp3", "pipe:pipe1"], stdout=subprocess.PIPE).stdout
return(sample)
def create_samp_2():
sample= subprocess.run(["ffmpeg", "-i", "https://freesound.org/data/previews/370/370934_6399962-lq.ogg", \
"-af", "adelay=1000|1000", "-f", "mp3", "pipe:pipe2"], 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", "pipe1", \
"-i", "pipe2", \
"-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()
create_pipes()
samp = create_samp()
samp_2 = create_samp_2()
record(samp, samp_2)
当我运行脚本时，create_samp() 和 create_samp2() 运行良好.但是我运行 record()，程序卡住了，没有错误消息，所以我无法弄清楚问题是什么.
When I run the script, create_samp() and create_samp2() are running fine. But I run record(), the program get stuck with no error message so I can't figure out what the issue is.
推荐答案
使用命名管道(仅限 Linux):
Using named pipes (Linux only):
当有两个或更多输入流(需要从内存缓冲区通过管道传输)时，需要命名管道.
使用命名管道一点也不简单...
Named pipes are required when there are two ore more input streams (that need to be piped from memory buffers).
Using named pipes is not trivial at all...
从 FFmpeg 的角度来看，命名管道就像(不可搜索的)输入文件.
From FFmpeg point of view named pipes are like (non-seekable) input files.
在 Python 中使用命名管道(在 Linux 中):
假设 pipe1 是命名管道"的名称.(例如 pipe1 = audio_pipe1").
Using named pipes in Python (in Linux):
Assume pipe1 is the name of the "named pipe" (e.g. pipe1 = "audio_pipe1").
创建一个命名管道":
Create a "named pipe":
os.mkfifo(pipe1)
以只写"方式打开管道文件:
Open the pipe as "write only" file:
fd_pipe = os.open(pipe_name, os.O_WRONLY) # fd_pipe1 is a file descriptor (an integer).
将数据以小块的形式写入管道.
根据这篇帖子，大多数管道的默认缓冲区大小Linux 系统为 64KBytes.
由于数据大于65536字节，我们需要将数据以小块的形式写入管道.
我决定使用 1024 字节的任意块大小.
管道写操作是一种阻塞"操作.操作.
我通过使用作家"解决了它线程:
Write the data to the pipe in small chunks.
According to this post, the default buffer size of the pipe in most Linux systems is 64KBytes.
Because the data is larger than 65536 bytes, we need to write the data to the pipe in small chunks.
I decided to use an arbitrary chunk size of 1024 bytes.
Pipe writing operation is a "blocking" operation.
I solved it by using a "writer" thread:
def writer(data, pipe_name, chunk_size):
# Open the pipes as opening "low level IO" files (open for "open for writing only").
fd_pipe = os.open(pipe_name, os.O_WRONLY) # fd_pipe1 is a file descriptor (an integer)
for i in range(0, len(data), chunk_size):
# Write to named pipe as writing to a "low level IO" file (but write the data in small chunks).
os.write(fd_pipe, data[i:chunk_size+i]) # Write 1024 bytes of data to fd_pipe
关闭管道:
Close the pipe:
os.close(fd_pipe)
移除(取消链接)命名管道:
Remove (unlink) the named pipe:
os.unlink(pipe1)
这是上一篇文章的示例，使用了两个命名管道:
Here is the sample from the previous post, using two named pipes:
import subprocess
import os
from threading import Thread
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.
sample1 = 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
# Read second audio sample from https://cdns-preview-b.dzcdn.net/stream/c-b0b684fe962f93dc43f1f7ea493683a1-3.mp3
sample2 = subprocess.run(["ffmpeg", "-i", "https://cdns-preview-b.dzcdn.net/stream/c-b0b684fe962f93dc43f1f7ea493683a1-3.mp3",
"-f", "mp3", "pipe:"], stdout=subprocess.PIPE).stdout
return sample1, sample2
def writer(data, pipe_name, chunk_size):
# Open the pipes as opening files (open for "open for writing only").
fd_pipe = os.open(pipe_name, os.O_WRONLY) # fd_pipe1 is a file descriptor (an integer)
for i in range(0, len(data), chunk_size):
# Write to named pipe as writing to a file (but write the data in small chunks).
os.write(fd_pipe, data[i:chunk_size+i]) # Write 1024 bytes of data to fd_pipe
# Closing the pipes as closing files.
os.close(fd_pipe)
def record(samp1, samp2):
# Names of the "Named pipes"
pipe1 = "audio_pipe1"
pipe2 = "audio_pipe2"
# Create "named pipes".
os.mkfifo(pipe1)
os.mkfifo(pipe2)
# Open FFmpeg as sub-process
# Use two audio input streams:
# 1. Named pipe: "audio_pipe1"
# 2. Named pipe: "audio_pipe2"
# 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", pipe1,
"-i", pipe2,
"-filter_complex", "amix=inputs=2:duration=longest", "output.mp3"],
stdin=subprocess.PIPE)
# Initialize two "writer" threads (each writer writes data to named pipe in chunks of 1024 bytes).
thread1 = Thread(target=writer, args=(samp1, pipe1, 1024)) # thread1 writes samp1 to pipe1
thread2 = Thread(target=writer, args=(samp2, pipe2, 1024)) # thread2 writes samp2 to pipe2
# Start the two threads
thread1.start()
thread2.start()
# Wait for the two writer threads to finish
thread1.join()
thread2.join()
process.wait() # Wait for FFmpeg sub-process to finish
# Remove the "named pipes".
os.unlink(pipe1)
os.unlink(pipe2)
sampl1, sampl2 = create_samp()
record(sampl1, sampl2)
更新:
使用类的相同解决方案:
使用类(NamedPipeWriter"类)实现解决方案更优雅一些.
该类继承了Thread类，并覆盖了run方法.
Update:
Same solution using a class:
Implementing the solution using a class ("NamedPipeWriter" class) is a bit more elegant.
The class inherits Thread class, and overrides run method.
您可以创建一个包含多个对象的列表，并在循环中迭代它们(而不是为每个新的输入流复制代码).
You may create a list of multiple objects, and iterate them in a loop, (instead of duplicating the code for each new input stream).
这是使用类的相同解决方案:
Here is the same solution using a class:
import subprocess
import os
import stat
from threading import Thread
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.
sample1 = 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
# Read second audio sample from https://cdns-preview-b.dzcdn.net/stream/c-b0b684fe962f93dc43f1f7ea493683a1-3.mp3
sample2 = subprocess.run(["ffmpeg", "-i", "https://cdns-preview-b.dzcdn.net/stream/c-b0b684fe962f93dc43f1f7ea493683a1-3.mp3",
"-f", "mp3", "pipe:"], stdout=subprocess.PIPE).stdout
return sample1, sample2
class NamedPipeWriter(Thread):
""" Write data (in small chunks) to a named pipe using a thread """
def __init__(self, pipe_name, data):
""" Initialization - get pipe name and data to be written """
super().__init__()
self._pipe_name = pipe_name
self._chunk_size = 1024
self._data = data
def run(self):
""" Open the pipe, write data in small chunks and close the pipe """
chunk_size = self._chunk_size
data = self._data
# Open the pipes as opening files (open for "open for writing only").
fd_pipe = os.open(self._pipe_name, os.O_WRONLY) # fd_pipe1 is a file descriptor (an integer)
for i in range(0, len(data), chunk_size):
# Write to named pipe as writing to a file (but write the data in small chunks).
os.write(fd_pipe, data[i:chunk_size+i]) # Write 1024 bytes of data to fd_pipe
# Closing the pipes as closing files.
os.close(fd_pipe)
def record(samp1, samp2):
# Names of the "Named pipes"
pipe1 = "audio_pipe1"
pipe2 = "audio_pipe2"
# Create "named pipes".
if not stat.S_ISFIFO(os.stat(pipe1).st_mode):
os.mkfifo(pipe1) # Create the pipe only if not exist.
if not stat.S_ISFIFO(os.stat(pipe2).st_mode):
os.mkfifo(pipe2)
# Open FFmpeg as sub-process
# Use two audio input streams:
# 1. Named pipe: "audio_pipe1"
# 2. Named pipe: "audio_pipe2"
# 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", pipe1,
"-i", pipe2,
"-filter_complex", "amix=inputs=2:duration=longest", "output.mp3"],
stdin=subprocess.PIPE)
# Initialize two "writer" threads (each writer writes data to named pipe in chunks of 1024 bytes).
named_pipe_writer1 = NamedPipeWriter(pipe1, samp1)
named_pipe_writer2 = NamedPipeWriter(pipe2, samp2)
# Start the two threads
named_pipe_writer1.start()
named_pipe_writer2.start()
# Wait for the two writer threads to finish
named_pipe_writer1.join()
named_pipe_writer1.join()
process.wait() # Wait for FFmpeg sub-process to finish
# Remove the "named pipes".
os.unlink(pipe1)
os.unlink(pipe2)
sampl1, sampl2 = create_samp()
record(sampl1, sampl2)
注意事项:
Notes:
- 代码已在 Ubuntu 18.04(在虚拟机中)测试.
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