如何将FFmpeg枚举的首个摄像头名称存入Python变量？

执行命令 ffmpeg -list_devices true -f dshow -i dummy 后得到以下FFmpeg输出：

ffmpeg version 2023-01-30-git-2d202985b7-full_build-www.gyan.dev Copyright (c) 2000-2023 the FFmpeg developers
  built with gcc 12.2.0 (Rev10, Built by MSYS2 project)
  configuration: --enable-gpl --enable-version3 --enable-static --disable-w32threads --disable-autodetect --enable-fontconfig --enable-iconv --enable-gnutls --enable-libxml2 --enable-gmp --enable-bzlib --enable-lzma --enable-libsnappy --enable-zlib --enable-librist --enable-libsrt --enable-libssh --enable-libzmq --enable-avisynth --enable-libbluray --enable-libcaca --enable-sdl2 --enable-libaribb24 --enable-libdav1d --enable-libdavs2 --enable-libuavs3d --enable-libzvbi --enable-librav1e --enable-libsvtav1 --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxavs2 --enable-libxvid --enable-libaom --enable-libjxl --enable-libopenjpeg --enable-libvpx --enable-mediafoundation --enable-libass --enable-frei0r --enable-libfreetype --enable-libfribidi --enable-liblensfun --enable-libvidstab --enable-libvmaf --enable-libzimg --enable-amf --enable-cuda-llvm --enable-cuvid --enable-ffnvcodec --enable-nvdec --enable-nvenc --enable-d3d11va --enable-dxva2 --enable-libvpl --enable-libshaderc --enable-vulkan --enable-libplacebo --enable-opencl --enable-libcdio --enable-libgme --enable-libmodplug --enable-libopenmpt --enable-libopencore-amrwb --enable-libmp3lame --enable-libshine --enable-libtheora --enable-libtwolame --enable-libvo-amrwbenc --enable-libilbc --enable-libgsm --enable-libopencore-amrnb --enable-libopus --enable-libspeex --enable-libvorbis --enable-ladspa --enable-libbs2b --enable-libflite --enable-libmysofa --enable-librubberband --enable-libsoxr --enable-chromaprint
  libavutil      57. 44.100 / 57. 44.100
  libavcodec     59. 59.100 / 59. 59.100
  libavformat    59. 36.100 / 59. 36.100
  libavdevice    59.  8.101 / 59.  8.101
  libavfilter     8. 56.100 /  8. 56.100
  libswscale      6.  8.112 /  6.  8.112
  libswresample   4.  9.100 /  4.  9.100
  libpostproc    56.  7.100 / 56.  7.100
[dshow @ 00000236357d0480] "HP True Vision HD Camera" (video)
[dshow @ 00000236357d0480]   Alternative name "@device_pnp_\\?\usb#vid_04f2&pid_b6ab&mi_00#6&763f234&2&0000#{65e8773d-8f56-11d0-a3b9-00a0c9223196}\global"
[dshow @ 00000236357d0480] "Microphone Array (Intel® Smart Sound Technology for Digital Microphones)" (audio)
[dshow @ 00000236357d0480]   Alternative name "@device_cm_{33D9A762-90C8-11D0-BD43-00A0C911CE86}\wave_{E8824DE9-F848-47F1-BB2A-EB24E11050FC}"
dummy: Immediate exit requested

需求是将输出中第一个视频设备名称「HP True Vision HD Camera」存入Python变量，请问该需求是否可实现？

用户尝试的Python代码：

import subprocess
ffmpeg_command = ["ffmpeg", "-list_devices", "true","-f", "dshow", "-i", "dummy"]
pipe = subprocess.run(ffmpeg_command,stdout=subprocess.PIPE,stderr=subprocess.PIPE,bufsize=10**8)
output = pipe.stdout
lines = output.splitlines()
for line in lines:
    if line.startswith("[dshow @"):
        if "(video)" in line:
            camera_info = line.split("\"")[1]
            print(camera_info)

这个需求完全可以实现，你当前代码的核心问题是：FFmpeg会把设备列表信息输出到标准错误流（stderr），而不是标准输出流（stdout），所以读取pipe.stdout拿不到目标内容。

修正后的代码如下：

import subprocess

ffmpeg_command = ["ffmpeg", "-list_devices", "true", "-f", "dshow", "-i", "dummy"]
pipe = subprocess.run(ffmpeg_command, stdout=subprocess.PIPE, stderr=subprocess.PIPE, bufsize=10**8)

# 从stderr读取输出并解码为字符串
output = pipe.stderr.decode('utf-8')
lines = output.splitlines()

camera_name = None
for line in lines:
    if line.startswith("[dshow @") and "(video)" in line:
        # 提取双引号包裹的设备名称
        camera_name = line.split('"')[1]
        break  # 找到第一个视频设备后停止遍历

if camera_name:
    print(f"提取到的第一个视频设备：{camera_name}")
    # 此时camera_name变量已存储目标值，可后续使用
else:
    print("未找到视频设备")

关键说明 #

• 切换读取pipe.stderr：FFmpeg的设备列表、版本信息等默认输出到stderr，而非stdout
• 字节流解码：subprocess返回的stderr是字节类型，需要用decode('utf-8')转换为字符串（如果是中文系统出现乱码，可尝试decode('gbk')）
• 提前终止循环：找到第一个符合条件的视频设备后用break跳出循环，提升效率

内容的提问来源于stack exchange，提问作者Chris P