Question

（关于ffmpeg我是新手）。我有一个图像源，该图像源以30 fps的速率将文件保存到给定的文件夹中。我想等待（假设）每30帧的数据块，将其编码为h264并通过RDP将其流式传输到其他应用程序。

我考虑过编写一个python应用程序，该应用程序仅等待图像，然后执行ffmpeg命令。为此，我编写了以下代码：

main.py：

import os
import Helpers
import argparse
import IniParser
import subprocess
from functools import partial

from Queue import Queue
from threading import Semaphore, Thread


def Run(config):

    os.chdir(config.Workdir)
    iteration = 1

    q = Queue()
    Thread(target=RunProcesses, args=(q, config.AllowedParallelRuns)).start()

    while True:

        Helpers.FileCount(config.FramesPathPattern, config.ChunkSize * iteration)

        command = config.FfmpegCommand.format(startNumber = (iteration-1)*config.ChunkSize, vFrames=config.ChunkSize)

        runFunction = partial(subprocess.Popen, command)
        q.put(runFunction)

        iteration += 1

def RunProcesses(queue, semaphoreSize):

    semaphore = Semaphore(semaphoreSize)

    while True:

        runFunction = queue.get()

        Thread(target=HandleProcess, args=(runFunction, semaphore)).start()

def HandleProcess(runFunction, semaphore):

    semaphore.acquire()

    p = runFunction()
    p.wait()

    semaphore.release()

if __name__ == '__main__':

    argparser = argparse.ArgumentParser()
    argparser.add_argument("config", type=str, help="Path for the config file")
    args = argparser.parse_args()

    iniFilePath = args.config

    config = IniParser.Parse(iniFilePath)

    Run(config)

Helpers.py（无关紧要）：

import os
import time
from glob import glob

def FileCount(pattern, count):

    count = int(count)

    lastCount = 0
    while True:

        currentCount = glob(pattern)

        if lastCount != currentCount:
            lastCount = currentCount

        if len(currentCount) >= count and all([CheckIfClosed(f) for f in currentCount]):

            break

        time.sleep(0.05)

def CheckIfClosed(filePath):

    try:
        os.rename(filePath, filePath)
        return True
    except:
        return False

我使用了以下配置文件：

Workdir = "C:\Developer\MyProjects\Streaming\OutputStream\PPM"
; Workdir is the directory of reference from which all paths are relative to.
; You may still use full paths if you wish.

FramesPathPattern = "F*.ppm"
; The path pattern (wildcards allowed) where the rendered images are stored to.
; We use this pattern to detect how many rendered images are available for streaming.
; When a chunk of frames is ready - we stream it (or store to disk).

ChunkSize = 30 ; Number of frames for bulk.
; ChunkSize sets the number of frames we need to wait for, in order to execute the ffmpeg command.
; If the folder already contains several chunks, it will first process the first chunk, then second, and so on...

AllowedParallelRuns = 1 ; Number of parallel allowed processes of ffmpeg.
; This sets how many parallel ffmpeg processes are allowed.
; If more than one chunk is available in the folder for processing, we will execute several ffmpeg processes in parallel.
; Only when on of the processes will finish, we will allow another process execution.

FfmpegCommand = "ffmpeg -re -r 30 -start_number {startNumber} -i F%08d.ppm -vframes {vFrames} -vf vflip -f rtp rtp://127.0.0.1:1234" ; Command to execute when a bulk is ready for streaming.
; Once a chunk is ready for processing, this is the command that will be executed (same as running it from the terminal).
; There is however a minor difference. Since every chunk starts with a different frame number, you can use the
; expression of "{startNumber}" which will automatically takes the value of the matching start frame number.
; You can also use "{vFrames}" as an expression for the ChunkSize which was set above in the "ChunkSize" entry.

请注意，如果我设置“ AllowedParallelRuns = 2”，那么它将允许多个ffmpeg进程同时运行。

然后我尝试用ffplay播放它，看看我是否做得对。第一块数据流很好。以下代码块不是很好。我收到很多[sdp @ 0000006de33c9180] RTP: dropping old packet received too late消息。

我应该怎么做才能使ffplay按传入图像的顺序播放？运行并行ffmpeg进程是否正确？我的问题有更好的解决方案吗？

谢谢！

Answer 1

正如我在评论中所述，由于您每次都重新运行ffmpeg，因此会重置pts值，但是客户端将其视为单个连续的ffmpeg流，因此期望增加PTS值。

正如我说过的，您可以使用ffmpeg python包装器自己控制流式传输，但是，是的，这是相当多的代码。但是，实际上有一个肮脏的解决方法。

因此，显然有一个num_layers参数，您可以使用它来抵消输入时间戳（请参阅FFmpeg documentation）。由于您知道并控制速率，因此可以通过此参数传递一个递增的值，以便每个下一个流都以适当的持续时间进行偏移。例如。如果您每次流式传输30帧，并且您知道fps为30，则这30帧将创建一秒的时间间隔。因此，在每次调用ffmepg时，您都会将model { ssd { anchor_generator { ssd_anchor_generator { num_layers: <num_of_feature_maps> ... } } } }的值增加一秒钟，因此应将其添加到输出的PTS值中。但是我不能保证这行得通。

由于关于-itsoffset的想法行不通，因此您也可以尝试通过stdin将jpeg图像馈送到ffmpeg-请参见this链接。

ffmpeg-文件的轮询文件夹，并使用rtp作为视频流

1 个答案: