我正在使用ffmpeg在rtsp流上流式传输树莓PI摄像头。
在我将此命令与OpenCV:结合使用之前
ffmpeg -re -c:v copy -preset ultrafast -tune zerolatency -rtsp_transport udp -f rtsp rtsp_server
它工作良好，但CPU使用率很高。
所以我发现有了这个命令
ffmpeg -input_format h264 -i /dev/video0 -c:v copy -an -rtsp_transport udp -f rtsp rtsp_server
我没有使用CPU，但在互联网上发送的数据量很高。
保存用最后一个命令捕获的视频，并使用mediainfo获取信息，它说：格式：AVI格式/信息：音频视频交错文件大小：2.52 MiB持续时间：17 s 783 ms总比特率：1 188 kb/s写作申请：Laff58.76.100
Video
ID : 0
Format : AVC
Format/Info : Advanced Video Codec
Format profile : High@L4
Format settings : CABAC / 1 Ref Frames
Format settings, CABAC : Yes
Format settings, Reference frames : 1 frame
Format settings, GOP : M=1, N=60
Codec ID : H264
Duration : 17 s 783 ms
Bit rate : 1 174 kb/s
Width : 640 pixels
Height : 480 pixels
Display aspect ratio : 4:3
Frame rate : 60.000 FPS
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Bits/(Pixel*Frame) : 0.064
Stream size : 2.49 MiB (99%)
我试着用这个命令来降低帧速率和比特率：
ffmpeg -input_format h264 -i /dev/video0 -b:v 30k -framerate 30 -c:v copy -an video.avi
但它不起作用。
这是我保存视频时的ffmpeg输出：
ffmpeg -input_format h264 -i /dev/video0 -b:v 30k -framerate 30 -c:v copy -an video.avi
ffmpeg version a4e1dd6 Copyright (c) 2000-2021 the FFmpeg developers
built with gcc 10 (Raspbian 10.2.1-6+rpi1)
configuration: --extra-cflags='-I/usr/local/include -I/usr/include' --extra-ldflags='-L/usr/local/lib -L/usr/lib' --extra-libs='-lpthread -lm -latomic' --arch=armel --enable-gmp --enable-gpl --enable-libaom --enable-libass --enable-libdav1d --enable-libdrm --enable-libfdk-aac --enable-libfreetype --enable-libkvazaar --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopus --enable-librtmp --enable-libsnappy --enable-libsoxr --enable-libssh --enable-libvorbis --enable-libvpx --enable-libzimg --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-mmal --enable-nonfree --enable-omx --enable-omx-rpi --enable-version3 --target-os=linux --enable-pthreads --enable-openssl --enable-hardcoded-tables
libavutil 56. 70.100 / 56. 70.100
libavcodec 58.134.100 / 58.134.100
libavformat 58. 76.100 / 58. 76.100
libavdevice 58. 13.100 / 58. 13.100
libavfilter 7.110.100 / 7.110.100
libswscale 5. 9.100 / 5. 9.100
libswresample 3. 9.100 / 3. 9.100
libpostproc 55. 9.100 / 55. 9.100
Input #0, video4linux2,v4l2, from '/dev/video0':
Duration: N/A, start: 14575.131904, bitrate: N/A
Stream #0:0: Video: h264 (High), yuv420p(progressive), 640x480, 30 fps, 30 tbr, 1000k tbn, 2000k tbc
Output #0, avi, to 'video.avi':
Metadata:
ISFT : Lavf58.76.100
Stream #0:0: Video: h264 (High) (H264 / 0x34363248), yuv420p(progressive), 640x480, q=2-31, 30 kb/s, 30 fps, 30 tbr, 60 tbn, 60 tbc
Stream mapping:
Stream #0:0 -> #0:0 (copy)
Press [q] to stop, [?] for help
[avi @ 0x3044850] Timestamps are unset in a packet for stream 0. This is deprecated and will stop working in the future. Fix your code to set the timestamps properly
frame= 1 fps=0.0 q=-1.0 size= 28kB time=00:00:00.01 bitrate=13675.9kbi[avi @ 0x3044850] Non-monotonous DTS in output stream 0:0; previous: 0, current: 0; changing to 1. This may result in incorrect timestamps in the output file.
frame= 23 fps=0.0 q=-1.0 size= 202kB time=00:00:00.71 bitrate=2305.9kbitframe= 38 fps= 37 q=-1.0 size= 256kB time=00:00:01.21 bitrate=1723.7kbitframe= 53 fps= 35 q=-1.0 size= 256kB time=00:00:01.71 bitrate=1221.6kbitframe= 69 fps= 34 q=-1.0 size= 512kB time=00:00:02.25 bitrate=1864.1kbitframe= 84 fps= 33 q=-1.0 size= 512kB time=00:00:02.75 bitrate=1525.2kbitframe= 99 fps= 33 q=-1.0 size= 768kB time=00:00:03.25 bitrate=1935.8kbitframe= 114 fps= 32 q=-1.0 size= 768kB time=00:00:03.75 bitrate=1677.7kbitframe= 129 fps= 32 q=-1.0 size= 1024kB time=00:00:04.25 bitrate=1973.8kbitframe= 144 fps= 32 q=-1.0 size= 1024kB time=00:00:04.75 bitrate=1766.0kbitframe= 159 fps= 31 q=-1.0 size= 1280kB time=00:00:05.25 bitrate=1997.3kbitframe= 175 fps= 31 q=-1.0 size= 1280kB time=00:00:05.78 bitrate=1813.1kbitframe= 190 fps= 31 q=-1.0 size= 1536kB time=00:00:06.28 bitrate=2002.6kbitframe= 205 fps= 31 q=-1.0 size= 1536kB time=00:00:06.78 bitrate=1855.0kbitframe= 220 fps= 31 q=-1.0 size= 1792kB time=00:00:07.28 bitrate=2015.6kbitframe= 235 fps= 31 q=-1.0 size= 1792kB time=00:00:07.78 bitrate=1886.1kbitframe= 251 fps= 31 q=-1.0 size= 2048kB time=00:00:08.31 bitrate=2017.3kbitframe= 266 fps= 31 q=-1.0 size= 2048kB time=00:00:08.81 bitrate=1902.9kbitframe= 279 fps= 31 q=-1.0 Lsize= 2315kB time=00:00:09.25 bitrate=2050.6kbits/s speed=1.02x
video:2297kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.816921%
有人能帮我缩小输出大小吗？
使用解决了v4l2的最大比特率设置问题
v4l2-ctl --set-ctrl video_bitrate=value_you_want