检查视频是否有声音，即使它有音频编解码器？

Question

我是中级 python 的新手，我正在尝试查找下载的视频是否有声音，我下载的每个视频都有一个音频编解码器，但我想获得该特定视频中音频的声音分贝。

例如，这个“FFmpeg”命令行脚本允许我获取完整信息：

ffmpeg -hide_banner -i testvideo.mp4 -af volumedetect -vn -f null - 2>&1

这会在我的命令提示符中产生以下结果（这里的 Windows 用户使用 win 11）

Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'testvideo.mp4':

Metadata:

major_brand : mp42

minor_version : 0

compatible_brands: mp42mp41isomavc1

creation_time : 2022-04-12T23:21:45.000000Z

Duration: 00:00:40.58, start: 0.000000, bitrate: 4104 kb/s

Stream #0:0[0x1](und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709, progressive), 1920x1080, 3846 kb/s, 29.97 fps, 29.97 tbr, 30k tbn (default)

Metadata:

creation_time : 2022-04-12T23:21:45.000000Z

handler_name : L-SMASH Video Handler

vendor_id : [0][0][0][0]

encoder : AVC Coding

Stream #0:1[0x2](und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 253 kb/s (default)

Metadata:

creation_time : 2022-04-12T23:21:45.000000Z

handler_name : L-SMASH Audio Handler

vendor_id : [0][0][0][0]

Stream mapping:

Stream #0:1 -> #0:0 (aac (native) -> pcm_s16le (native))

Press [q] to stop, [?] for help

Output #0, null, to 'pipe:':

Metadata:

major_brand : mp42

minor_version : 0

compatible_brands: mp42mp41isomavc1

encoder : Lavf59.35.100

Stream #0:0(und): Audio: pcm_s16le, 48000 Hz, stereo, s16, 1536 kb/s (default)

Metadata:

creation_time : 2022-04-12T23:21:45.000000Z

handler_name : L-SMASH Audio Handler

vendor_id : [0][0][0][0]

encoder : Lavc59.56.100 pcm_s16le

size=N/A time=00:00:40.55 bitrate=N/A speed=1.22e+03x

video:0kB audio:7608kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown

[Parsed_volumedetect_0 @ 0000026609be08c0] n_samples: 3895296

[Parsed_volumedetect_0 @ 0000026609be08c0] mean_volume: -91.0 dB

[Parsed_volumedetect_0 @ 0000026609be08c0] max_volume: -91.0 dB

[Parsed_volumedetect_0 @ 0000026609be08c0] histogram_91db: 3895296

如您所见，“parsed_volumedetect”值为 dB，其平均值为 -91 dB，这意味着音频没有声音，即视频有音频但没有声音。

现在我想在 python 中做同样的事情，我只想将平均音量值存储在一个变量中，这样我就可以检查视频中是否有声音。

到目前为止，我已经看到了子进程代码，但是当我尝试在 VS-Code 中运行我的代码时 - python 3.11：

import subprocess    
result = subprocess.run(["ffmpeg", "-hide_banner", "-af", "volumedetect", "-vn", "-f", "null", "testvideo1.mp4"],
    stdout=subprocess.PIPE,
    stderr=subprocess.STDOUT,
    shell=True)
    print(result.stdout)

它说：

PS C:\Users\balaj\OneDrive\Documents\Programming language\python files> c:; cd 'c:\Users\balaj\OneDrive\Documents\Programming language\python files'; & 'C:\Python311\python.exe' 'c:\Users\balaj\.vscode\extensions\ms-python.python-2022.20.2\pythonFiles\lib\python\debugpy\adapter/../..\debugpy\launcher' '51760' '--' 'c:\Users\balaj\OneDrive\Documents\Programming language\python files\devproject\sample.py'

b"Output #0, null, to 'testvideo1.mp4':\r\nOutput file #0 does not contain any stream\r\n"

任何帮助深表感谢。 抱歉发了这么长的帖子……TIA！！！

只是一个快速更新：对于有声音（我在 VLC 中测试过）和没有声音的视频文件，结果是一样的。

另一个更新：我已将subprocess.run代码更改为与我在 cmd windows 中调用的代码完全相同：

result = subprocess.run(["ffmpeg", "-hide_banner","-i","testvideo-sound.mp4", "-af", "volumedetect", "-vn", "-f", "null", "-2>&1"]

现在结果是这样的：

b'The handle could not be duplicated\r\nduring redirection of handle 1.\r\n'

Answer 1

这似乎对我有用。 我用我身边的几个不同的视频文件 (mp4) 进行了尝试。

import subprocess
import re

files = [
    # list of file paths
]

def find_volume(s):
    # regex to find volume in a string
    m = re.search("(?:max_volume: )(?P<volume>.+ dB)", s, flags=re.IGNORECASE)
    
    if not m:
        return None

    return m.groupdict()["volume"]

    

for filepath in files:
    r = subprocess.run(f'ffmpeg -i "{filepath}" -filter:a volumedetect -f null /dev/null',
            stdout=subprocess.PIPE,
            stderr=subprocess.STDOUT,
            shell=True
    )
    # "volume" will be either None or a string;
    # if it is none, we go to do to the "else" body
    # instead, because None if 'falsy'.
    if volume := find_volume(r.stdout.decode("utf-8")):
        print(f'Video file "{filepath}" has a max volume of {volume}')
    else:
        print(f'Video file "{filepath}" has no audio')