Java 調用 FFMPEG 的坑人之處

昨天用 ubuntu 20.04 安裝的 ffmpeg 進行視頻轉碼時，出現了一個奇葩的問題，用命令行能過的指令，經過 Java 調用死活不行。原來Java 調用的默認容許協議與命令行的居然不同（至於爲何不同，尚未找到答案...）。

Java 調用 FFMPEG 命令時用 url 做爲輸入源，Linux 下出現 「no such file or directory」 問題的解決

ffmpeg version 4.2.2-1ubuntu1 Copyright (c) 2000-2019 the FFmpeg developers
  built with gcc 9 (Ubuntu 9.3.0-3ubuntu1)
  configuration: --prefix=/usr --extra-version=1ubuntu1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --arch=amd64
 --enable-gpl --disable-stripping --enable-avresample --disable-filter=resample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libaom --enable-libass -
-enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libf
ribidi --enable-libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-l
ibpulse --enable-librsvg --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable
-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable
-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opencl --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-libdrm --enable-libiec
61883 --enable-nvenc --enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared
  libavutil      56. 31.100 / 56. 31.100
  libavcodec     58. 54.100 / 58. 54.100
  libavformat    58. 29.100 / 58. 29.100
  libavdevice    58.  8.100 / 58.  8.100
  libavfilter     7. 57.100 /  7. 57.100
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  5.100 /  5.  5.100
  libswresample   3.  5.100 /  3.  5.100
  libpostproc    55.  5.100 / 55.  5.100
"https://video.example.com/video/ece851398dba2dc26df0e9ccba7fbe00/MULTI-ece851398dba2dc26df0e9ccba7fbe00-130961929/videos_200.mp4": No such file or directory

這個No such file or directory 根本不是文件不存在，下載到本地也會報一樣的錯

經過'ffmpeg -loglevel debug' 首先增長調試參數。
你會看到錯誤輸出：

ffmpeg version 4.2.2-1ubuntu1 Copyright (c) 2000-2019 the ...
Reading option '-loglevel' ... matched as option 'loglevel' (set logging level) with argument 'debug'.
0-130961929/videos_200.mp4"'.
Reading option '-vcodec' ... matched as option 'vcodec' (force video codec ('copy' to copy stream)) with argument 'libwebp'.
Reading option '-lossless' ... matched as AVOption 'lossless' with argument '0'.
Reading option '-qscale' ... matched as option 'qscale' (use fixed quality scale (VBR)) with argument '75'.
Reading option '-preset' ... matched as AVOption 'preset' with argument 'default'.
Reading option '-loop' ... matched as AVOption 'loop' with argument '0'.
Reading option '-an' ... matched as option 'an' (disable audio) with argument '1'.
Reading option '-vsync' ... matched as option 'vsync' (video sync method) with argument '0'.
Reading option '/tmp/output.webp' ... matched as output url.
Finished splitting the commandline.
Parsing a group of options: global .
Applying option loglevel (set logging level) with argument debug.
Applying option vsync (video sync method) with argument 0.
Successfully parsed a group of options.
Parsing a group of options: input url "https://video.example.com/video/ece851398dba2dc26df0e9ccba7fbe00/MULTI-ece851398dba2dc26df0e9ccba7fbe00-130961929/videos_200
.mp4".
Applying option c (codec name) with argument /bin/sh.
Successfully parsed a group of options.
Opening an input file: "https://video.example.com/video/ece851398dba2dc26df0e9ccba7fbe00/MULTI-ece851398dba2dc26df0e9ccba7fbe00-130961929/videos_200.mp4".
[NULL @ 0x55fd7533f440] Opening '"https://video.example.com/video/ece851398dba2dc26df0e9ccba7fbe00/MULTI-ece851398dba2dc26df0e9ccba7fbe00-130961929/videos_200.mp4"
' for reading
[file @ 0x55fd7533fec0] Setting default whitelist 'file,crypto'
"https://video.example.com/video/ece851398dba2dc26df0e9ccba7fbe00/MULTI-ece851398dba2dc26df0e9ccba7fbe00-130961929/videos_200.mp4": No such file or directory

這裏最重要的信息是

Setting default whitelist 'file,crypto'

在搜索過程如下兩個連接很是有幫助：

https://blog.yo1.dog/fix-for-...

https://stackoverflow.com/a/1...

能夠經過參數 '-report' 將完整的命令行和控制檯輸出轉儲到當前目錄中名爲 program-YYYYMMDD-HHMMSS.log 的文件中。該文件對於調試錯誤頗有用。它默認爲-loglevel verbose級別的日誌輸出。也能夠經過設置FFREPORT環境變量來實現一樣的效果:

FFREPORT="level=32:file=abc.log" ffmpeg -v verbose ...

如下是上面第一個連接的翻譯：

修復FFmpeg「協議不在白名單上」 HTTP（S）URL錯誤

使用-safe 0和-protocol_whitelist file,http,https,tcp,tls 參數。完整示例在最底部。

---

我試圖像這樣使用FFmpeg的concat多路分配器：

# inputs.txt
file 'http://www.example1.com/video1.mp4'  
file 'https://www.example2.com/video2.mp4'

ffmpeg -f "concat" -i "./inputs.txt" -codec "copy" "./concated.mp4"

首先我獲得了錯誤：

[concat @ 0x00] Unsafe file name 'http://www.example1.com/video1.mp4'
./inputs.txt: Operation not permitted

這經過添加-safe 0參數來解決。而後我獲得了錯誤：

[http @ 0x00] Protocol not on whitelist 'file,crypto'!
[concat @ 0x00] Impossible to open 'http://www.example1.com/video1.mp4'
./inputs.txt: Invalid argument

我覺得我能夠經過簡單的添加來解決這個問題，-protocol_whitelist file,http,https可是錯誤變成了：

[tcp @ 0x00] Protocol not on whitelist 'file,http,https'!
[concat @ 0x00] Impossible to open 'http://www.example1.com/video1.mp4'
./inputs.txt: Invalid argument

我不明白爲何個人HTTP協議輸入仍然被拒絕。http顯然在協議白名單中。而後，我注意到前兩個錯誤之間的差異很小。看那些錯誤中的第一個單詞。httpVS tcp。我意識到錯誤以前括號中的第一個單詞是被拒絕的協議。

解決方案是也要添加tcp到協議白名單中（tls若是要支持HTTPS ，也要添加到協議白名單中）。這是個人最終命令：

ffmpeg -f "concat" -safe "0" -protocol_whitelist "file,http,https,tcp,tls" -i "./inputs.txt" -codec "copy" "./concated.mp4"