ffmpeg command

1. ffplay -f s16le -ar 44100 -ac 2 pcm_file.pcm
2. ffmpeg -i Warcraft3_End3.mp4 -vn -acodec pcm_s16le -f s16le -ac 1 -ar 16000 output.pcm
3. ffmpeg -i xxx.h264 -s 720*576 -pix_fmt yuv420p v.yuv
4. ffplay -f rawvideo -pixel_format yuv420p -video_size 720*576 v.yuv

localhost:~/develop/opensource/ffmpeg # ffmpeg -f v4l2 -list_formats all -i /dev/video0
ffmpeg version 4.1.git Copyright (c) 2000-2019 the FFmpeg developers
 built with gcc 5.5.0 (GCC)
 configuration: --prefix=/root/develop/software/ffmpeg --enable-gpl --enable-nonfree --enable-openssl --enable-libv4l2 --enable-libx264 --enable-libx265 --enable-opengl --enable-opencl --enable-alsa --enable-libpulse --enable-cuda-nvcc --enable-libnpp --extra-cflags=
-I/usr/local/cuda/include --extra-ldflags=-L/usr/local/cuda/lib64 --enable-libmfx --enable-encoder=h264_qsv --enable-decoder=h264_qsv
 libavutil      56. 30.100 / 56. 30.100
 libavcodec     58. 53.101 / 58. 53.101
 libavformat    58. 28.102 / 58. 28.102
 libavdevice    58.  7.100 / 58.  7.100
 libavfilter     7. 56.101 /  7. 56.101
 libswscale      5.  4.101 /  5.  4.101
 libswresample   3.  4.100 /  3.  4.100
 libpostproc    55.  4.100 / 55.  4.100
[video4linux2,v4l2 @ 0x25e1d80] Raw       :     yuyv422 :           YUYV 4:2:2 : 640x480 320x180 320x240 352x288 424x240 640x360 848x480 960x540 1280x720
[video4linux2,v4l2 @ 0x25e1d80] Compressed:       mjpeg :          Motion-JPEG : 640x480 320x180 320x240 352x288 424x240 640x360 848x480 960x540 1280x720

 

ffplay -f v4l2 -i /dev/video0

 

./ffmpeg_g -i ~/Downloads/onedream.mp4 -ss 00:01:00 -q:v 78 -frames:v 1 5.jpeg -y

     

-q:v 78  ---> qscale-->enc_ctx->global_quality

  ost->enc_ctx->flags |= AV_CODEC_FLAG_QSCALE;
        ost->enc_ctx->global_quality = FF_QP2LAMBDA * qscale;