FFmpeg collection and memo.

🌵 Install

This is the simplest and least error-prone method to install ffmpeg.

Get builds from FFmpeg.ory, and set your shell PATH.

Note that pip install opencv-python install OpenCV has some problems like not support x264. Better use following way to install OpenCV.

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conda install x264=='1!152.20180717' ffmpeg=4.0.2 -c conda-forge
conda install opencv

注意： 使用上述命令安装支持读写 x264 的 OpenCV，之后再删除通过 conda 安装的 ffmpeg，改为静态库版本。因为通过 conda 安装的 ffmpeg 不支持 mp3 的读写。

stackoverflow: How to use libx264 ffmpeg in conda environment?

Another way is to build ffmpeg from source.

FFMPEG: Compile FFmpeg on CentOS

You can build static or dynamic libs.

🚩注意： 当编译动态库版本的 ffmpeg 时，其依赖也需要编译成动态库版本。如果需要编译动态库版本的 OpenCV，ffmpeg 也需要使用动态库。

👍stackoverflow: FFmpeg doesn’t compile with shared libraries

⁋ Problem & Solution

⁋ libaom.a cannot be used when making a shared object

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/usr/bin/ld: /home/rivergold/software/lib/ffmpeg/ffmpeg-build/lib/libaom.a(noise_model.c.o): relocation R_X86_64_PC32 against symbol `stderr@@GLIBC_2.2.5' can not be used when making a shared object; recompile with -fPIC

Solution:

Build libaom with enable shared libs.

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# libaom
cd ${FFPEG_SOURCE_DIR} &&
    mkdir -p aom_build &&
    cd aom_build &&
    PATH="$PREFIX_DIR/bin:$PATH" cmake -G "Unix Makefiles" -DCMAKE_INSTALL_PREFIX="$PREFIX_DIR" -DBUILD_SHARED_LIBS=on -DENABLE_NASM=on ../aom &&
    PATH="$PREFIX_DIR/bin:$PATH" make &&
    make install

注意： ffmpeg 官网的教程仅说明了如何编译 static 版本的 ffmpeg，且编译libaom的参数ENABLE_SHARED在 CMakeLists.txt 中没有记录，需要改为BUILD_SHARED_LIBS

🌵 Get Video Information

mediainfo is a very good tool to get media information. And pymediainfo is Python API of mediainfo.

⁋ Install mediainfo

  1. Download CLI, libmediainfo and libzen

  2. Install

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    rpm -i libzen
    rpm -i libmediainfo
    rpm cli

⁋ ffprobe get json format information

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ffprobe -print_format json <video>

Github Gist: jaivikram/getVideoDetails.py
Github Gist: oldo/video-metada-finder.py

🌵 Change Video Format

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ffmpeg -i <in_video_path> -c copy <out_video_path>

E.g.

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ffmpeg -i in.ts -c copy out.mp4

🌵 Change Video Encode Format

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ffmpeg -i <in_video_path> -c:v <video_encode> -c:a copy <out_video_path>

E.g.

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ffmpeg -i in.ts -c:v libx264 -c:a copy out.mp4

⁋ Change Encode while Keep Bitrate

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ffmpeg -i <in_video_path> -c:v <video_encode> -b:v <video_bitrate> -c:a copy <out_video_path>

E.g.

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ffmpeg -i in.ts -c:v libx264 -b:v 20M -c:a copy out.mp4

stackoverflow: How to convert .ts file into a mainstream format losslessly?

🌵 Extract Frame from Video

⁋ Extract One Frame

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ffmpeg -ss <time> -i <input_video> -vframes 1 -q:v 2 output.jpg

stackoverflow: How to extract 1 screenshot for a video with ffmpeg at a given time?

⁋ Extract All Frame

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ffmpeg -loglevel warning -y -vsync 0 -i <in_video_path> -vf "select=between(n\,1\,300000)*not(mod(n\,1))" -q:v 0 -deinterlace frm_%d.jpg

@rivergold: 该命令会舍弃视频的第一帧（0 号帧）。因为 FFmpeg 导出图片时 index 是从 1 开始计数的，如果舍弃第一帧，则帧号与从 0 开始计数的方式保持一致。

🌵 Cut Video

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# start_time, end_time
ffmpeg -ss <start_time> -to <end_time> -i <in_video_path> <out_video_path>
# start_time, duration
ffmepg -ss <start_time> -t <duration> -i <in_video_path> <out_video_path>