主要用于记录常用的命令行。
文章目录
ffmpeg 命令行使用
查看音频和视频设备列表：
- win:
ffmpeg -f dshow -list_devices true -i dummpy
[dshow @ 000002266c527fc0] "Microsoft® LifeCam Studio(TM)" (video)
[dshow @ 000002266c527fc0] Alternative name "@device_pnp_\\?\usb#vid_045e&pid...
[dshow @ 000002266c527fc0] "PRISM Live Studio" (video)
[dshow @ 000002266c527fc0] Alternative name "@device_sw_{860BB310-5D01-11D0-BD3B-00A0C911CE86}\{A49F51EE-8841-4425-BEC0-85D0C470BBDE}"
[dshow @ 000002266c527fc0] "桌面麦克风 (Microsoft® LifeCam Studio(TM))" (audio)
[dshow @ 000002266c527fc0] Alternative name "@device_cm_{33D9A762-90C8-11D0-BD43-00A0C911CE86}\wave_{85A88CC0-ADB6-4E97-BB5D-AD3AAB334541}"
[dshow @ 000002266c527fc0] "FrontMic (Realtek(R) Audio)" (audio)
[dshow @ 000002266c527fc0] Alternative name "@device_cm_{33D9A762-90C8-11D0-BD43-00A0C911CE86}\wave_{7A5C2EBB-2C09-402A-B380-D250BFF4588E}"
- mac:
ffmpeg -f avfoundation -list_devices true -i dummpy
[AVFoundation indev @ 0x7f82ce905040] AVFoundation video devices:
[AVFoundation indev @ 0x7f82ce905040] [0] FaceTime HD Camera
[AVFoundation indev @ 0x7f82ce905040] [1] Capture screen 0
[AVFoundation indev @ 0x7f82ce905040] [2] Capture screen 1
[AVFoundation indev @ 0x7f82ce905040] AVFoundation audio devices:
[AVFoundation indev @ 0x7f82ce905040] [0] Built-in Microphone
[AVFoundation indev @ 0x7f82ce905040] [1] PRISM Live Studio
查看Dshow/Avfoundation库支持的具体支持参数：
- MAC :
ffmpeg -h demuxer=avfoundation
查看 avfoundation 的可支持的具体命令，比如avfoundation 就不支持dshow的list_options命令
Demuxer avfoundation [AVFoundation input device]:
AVFoundation indev AVOptions:
-list_devices <boolean> .D......... list available devices (default false)
-video_device_index <int> .D......... select video device by index for devices with same name ...
-audio_device_index <int> .D......... select audio device by index for devices with same name ...
-pixel_format <pix_fmt> .D......... set pixel format (default yuv420p)
-framerate <video_rate> .D......... set frame rate (default "ntsc")
-video_size <image_size> .D......... set video size
-capture_cursor <boolean> .D......... capture the screen cursor (default false)
......等
- WIN :
ffmpeg -h demuxer=dshow
Demuxer dshow [DirectShow capture]:
dshow indev AVOptions:
-video_size <image_size> .D......... set video size given a...
-pixel_format <pix_fmt> .D......... set video pixel format (default none)
-framerate <string> .D......... set video frame rate
-sample_rate <int> .D......... set audio sample rate ...
-sample_size <int> .D......... set audio sample size (from 0 to 16) (default 0)
-channels <int> .D......... set number of audio channels, ...
-audio_buffer_size <int> .D......... set audio device buffer latency size in ...
-list_devices <boolean> .D......... list available devices (default false)
-list_options <boolean> .D......... list available options for specified device...
......等
查看具体设备的支持分辨率或采样格式等列表：
- WIN Video:
ffmpeg -f dshow -list_options true -i video="Microsoft® LifeCam Studio(TM)"
[dshow @ 0000026dba738040] DirectShow video device options (from video devices)
[dshow @ 0000026dba738040] Pin "捕获" (alternative pin name "捕获")
[dshow @ 0000026dba738040] pixel_format=yuyv422 min s=640x480 fps=7.5 max s=640x480 fps=30
[dshow @ 0000026dba738040] pixel_format=yuyv422 min s=960x544 fps=7.5 max s=960x544 fps=20
[dshow @ 0000026dba738040] pixel_format=yuyv422 min s=800x448 fps=7.5 max s=800x448 fps=30
......等
- WIN Aduio:
ffmpeg -f dshow -list_options true -i audio="桌面麦克风 (Microsoft® LifeCam Studio(TM))"
[dshow @ 0000019c5c2b8040] DirectShow audio only device options (from audio devices)
[dshow @ 0000019c5c2b8040] Pin "Capture" (alternative pin name "Capture")
[dshow @ 0000019c5c2b8040] ch= 2, bits=16, rate= 44100
[dshow @ 0000019c5c2b8040] ch= 1, bits=16, rate= 44100
[dshow @ 0000019c5c2b8040] ch= 2, bits=16, rate= 32000
[dshow @ 0000019c5c2b8040] ch= 1, bits=16, rate= 32000
[dshow @ 0000019c5c2b8040] ch= 2, bits=16, rate= 22050
......等
录音：
前置说明： -i v:a 冒号前面是video编号，后面是audio编号，如果只有摄像头采集的话冒号可以省略
默认参数版：
-mac: ffmpeg -f avfoundation -i :0 out.wav
-win: ffmpeg -f dshow -i audio="麦克风 (Razer Seiren)" out.wav
带参数版：
-win： ffmpeg -f dshow -sample_rate 44100 -sample_size 16 -channels 2 -i audio="麦克风 (Razer Seiren)" out.wav
播放pcm：
ffplay -ar 44100 -ac 2 -f s16le out.pcm pcm必须带必须的传入参数
视频:
基本配置选项： -video_size -pixel_format framerate
录屏:
如果 -video_size -pixel_format framerate 都不写也能成功，只是会设置默认值。 查看设备支持的具体参数可以参考上面的list_options.
- WIN:
ffmpeg -f dshow -video_size 1920x1080 -pixel_format yuyv422 -i video="Microsoft® LifeCam Studio(TM)" out1.yuv - mac:
ffmpeg -f avfoundation -framerate 30 -i 0: out.yuv,0:可以省略成0。
mac不能查看设备支持的具体参数，可以在上条命令报错的时候，会列出支持的具体数据。 比如如果framerate不设置可以报错，
播放yuv
ffplay -pixel_format yuyv422 -video_size 1920x1080 out1.yuv
转换 format格式
ffmpeg -i 640x480.jpg -pix_fmt yuv420p out_yuv420p.yuv将 yuvj420p 转换成 yuv420p 成功。ffmpeg -i 640x480.jpg -pixel_format yuv420p out_yuv420p.yuv格式转换失败。-pixel_format用后，转换出的格式还是yuvj420p。
视频编码
ffmpeg -pix_fmt yuv420p -video_size 640x480 -i movie_640x480_yuv420p.yuv -c:v libx264 -r 30 ffmpge_640x480_yuv420p.h264将yuv 编码成 h264
-r 30代表输出 30fps
音视频解封装
- mp4 -> h264:
ffmpeg -i test.mp4 -c:v copy -an output.h264, 丢弃音频流，只保存视频流 - mp4 -> aac:
ffmpeg -i test.mp4 -c:a copy -vn output.aac, 丢弃视频流，只保存音频流 - h264 -> yuv:
ffmpeg -c:v h264 -i output.h264 out.yuv, h264 解码成yuv - aac -> pcm:
ffmpeg -c:a aac -i output.aac out.pcm, aac 解码成pcm
基础知识
linesize
- linesize 在 线性PCM 中代表， 多个声道的总大小 = nChannels * 位深(AVSampleFormat) >> 3
- 在 planner 中，代表一个单声道数据的大小 = 位深 >> 3
样本帧
- 代表一个大样本（包含多个声道的样本）
- 每个声道代表一个小样本