python - 不使用 shell-True 提取帧数

Question

我有以下代码从视频中提取帧数:

filename = "test.mp4"
video_path = os.path.join(os.getcwd(), filename)
with open(video_path, "rb") as file:
    cmd = f'ffmpeg -i {video_path} -r 10 -q:v 3 -s 1x1 -f image2 -update 1 - >/dev/null'
    proc = sp.Popen(cmd, stdout=sp.PIPE, stderr=sp.PIPE, shell=True)
    (stdout, stderr) = proc.communicate()

    # i.e: 'frame= 2062 fps=966 q=3.0 Lsize=N/A time=00:10:34.46 bitrate=N/A dup=1049 drop=3563 speed= 297x'
    decoded = stderr.decode('utf-8')
    frame_count_line = decoded.splitlines()[-2]
    m = FRAME_COUNT_REGEX.search(frame_count_line)
    if m:
        print(int(m.groups()[0]))

但出于安全原因，我想删除 shell=True范围。
不幸的是，之后上面的代码抛出:

FileNotFoundError: [Errno 2] No such file or directory

请帮忙修复

Answer 1

将您的命令放入列表中，例如

import subprocess
media = 'some media.mp4'
try:
    comm = subprocess.Popen(['ffmpeg', '-hide_banner', '-i', media, '-f', 'null', '-'],
                              stdout=subprocess.PIPE, stderr=subprocess.STDOUT, universal_newlines=True)
except Exception as e:
    print("Error: ", str(e))

try:
    with comm.stdout:
        for i in iter(comm.stdout.readline, b''):
            if i != '':
                print(i.strip())
            else:
                break
except Exception as e:
    print("Error: ", str(e))

您也可以使用 ffprobe而不是 ffmpeg因为ffprobe允许您选择 -count_frames 之类的内容和 -show_frames .
计数帧只会输出最终的数字，所以如果你需要显示发生了什么，你可能会更好 -show_frames .
例如

ffprobe -show_frames -count_frames -v error -select_streams v:0 -show_entries stream=nb_read_frames -show_entries frame=coded_picture_number -of default=nokey=1:noprint_wrappers=1 -i media

或者

ffprobe -count_frames -v error -select_streams v:0 -show_entries stream=nb_read_frames -of default=nokey=1:noprint_wrappers=1 -i media

或者

ffprobe -show_frames -v error -select_streams v:0 -show_entries frame=coded_picture_number -of default=nokey=1:noprint_wrappers=1 -i media