帧率ffmepg 摄像头_ffmpeg录屏/录音/录摄像头----命令行实现

秒速五厘米 2023-01-10 05:16 147阅读 0赞

ffmpeg在linux下支持的采集设备的种类比较多。

在操作设备之前，我们可以查看当前系统可以支持的操作设备：

ffmpeg -hide\_banner -devices

Devices:

D. = Demuxing supported //输入的设备

.E = Muxing supported //输出的设备

\--

DE alsa ALSA audio output

D dv1394 DV1394 A/V grab

DE fbdev Linux framebuffer //为输入输出设备，其他的类似这样判断

D lavfi Libavfilter virtual input device

DE oss OSS (Open Sound System) playback

E sdl SDL output device

E v4l2 Video4Linux2 output device

D video4linux2,v4l2 Video4Linux2 device grab

D x11grab X11 screen capture, using XCB

///

采集设备fbdev的参数:我们能看出fb(FrameBuffer)的操作参数，指定帧率就行(默认值为25).

ffmpeg -h demuxer=fbdev

Demuxer fbdev \[Linux framebuffer\]:

fbdev indev AVOptions:

\-framerate .D...... (default "25")

ffmpeg -framerate 30 -f fbdev -i /dev/fb0 out.mp4

v4l2 即就是video4linux2的缩写，也是常见视频设备。获取摄像头的视频图片～

通过ffmpeg -h demuxer=v4l2 查看相关的操作参数

V4L2 indev AVOptions:

\-standard .D...... set TV standard, used only by analog frame grabber

\-channel .D...... set TV channel, used only by frame grabber (from -1 to INT\_MAX) (default -1)

\-video\_size .D...... set frame size

\-pixel\_format .D...... set preferred pixel format

\-input\_format .D...... set preferred pixel format (for raw video) or codec name

\-framerate .D...... set frame rate

\-list\_formats .D...... list available formats and exit (from 0 to INT\_MAX) (default 0)

all .D...... show all available formats

raw .D...... show only non-compressed formats

compressed .D...... show only compressed formats

\-list\_standards .D...... list supported standards and exit (from 0 to 1) (default 0)

all .D...... show all supported standards

\-timestamps .D...... set type of timestamps for grabbed frames (from 0 to 2) (default default)

default .D...... use timestamps from the kernel

abs .D...... use absolute timestamps (wall clock)

mono2abs .D...... force conversion from monotonic to absolute timestamps

\-ts .D...... set type of timestamps for grabbed frames (from 0 to 2) (default default)

default .D...... use timestamps from the kernel

abs .D...... use absolute timestamps (wall clock)

mono2abs .D...... force conversion from monotonic to absolute timestamps

\-use\_libv4l2 .D...... use libv4l2 (v4l-utils) conversion functions (default false)

例子：

获取本电脑的v4l2摄像头所支持的色彩格式和分辨率：

ffmpeg -hide\_banner -f v4l2 -list\_formats all -i /dev/video0

\[video4linux2,v4l2 @ 0x9554e0\] Raw : yuyv422 : YUV 4:2:2 (YUYV)

: 640x480 320x240 352x288 160x120 176x144 1280x720

\[video4linux2,v4l2 @ 0x9554e0\] Compressed: mjpeg : MJPEG

: 640x480 320x240 352x288 160x120 176x144 1280x720

接下来可以使用下面的命令行，用摄像头采集视频文件：

ffmpeg -hide\_banner -s 1920\*1080 -i /dev/video0 out2.avi

对应的输出信息为：

\[video4linux2,v4l2 @ 0x15d0540\] The V4L2 driver changed the video from 1920x1080 to 1280x720

Input \#0, video4linux2,v4l2, from '/dev/video0':

Duration: N/A, start: 611.836289, bitrate: 110592 kb/s

Stream \#0:0: Video: rawvideo (YUY2 / 0x32595559), yuyv422, 1280x720, 110592 kb/s, 7.50 fps, 7.50 tbr, 1000k tbn, 1000k tbc

Output \#0, avi, to 'out2.avi':

Metadata:

ISFT : Lavf57.25.100

Stream \#0:0: Video: mpeg4 (FMP4 / 0x34504D46), yuv420p, 1280x720, q=2-31, 200 kb/s, 7.50 fps, 7.50 tbn, 7.50 tbc

Metadata:

encoder : Lavc57.24.102 mpeg4

Side data:

unknown side data type 10 (24 bytes)

Stream mapping:

Stream \#0:0 -> \#0:0 (rawvideo (native) -> mpeg4 (native))

因为我的摄像头不支持19201080，默认还原成了前面他所支持的参数 1280720,输出的视频编码采用了avi的默认编码和码率参数。

ffmpeg在linux下桌面图形的时候，通常是用x11grab设备采集桌面图像。

ffmpeg -h demuxer=x11grab 可以获得操作的参数：

Demuxer x11grab \[X11 screen capture, using XCB\]:

xcbgrab indev AVOptions:

\-x .D...... Initial x coordinate. (from 0 to INT\_MAX) (default 0)

\-y .D...... Initial y coordinate. (from 0 to INT\_MAX) (default 0)

\-grab\_x .D...... Initial x coordinate. (from 0 to INT\_MAX) (default 0)

\-grab\_y .D...... Initial y coordinate. (from 0 to INT\_MAX) (default 0)

\-video\_size .D...... A string describing frame size, such as 640x480 or hd720. (default "vga")

\-framerate .D...... (default "ntsc")

\-draw\_mouse .D...... Draw the mouse pointer. (from 0 to 1) (default 1)

\-follow\_mouse .D...... Move the grabbing region when the mouse pointer reaches within specified

amount of pixels to the edge of region. (from -1 to INT\_MAX) (default 0)

centered .D...... Keep the mouse pointer at the center of grabbing region when following.

\-show\_region .D...... Show the grabbing region. (from 0 to 1) (default 0)

\-region\_border .D...... Set the region border thickness. (from 1 to 128) (default 3)

参数包括了，采集分辨率-video\_size ， 支持鼠标光标 -draw\_mouse， 跟中鼠标轨迹 -follow\_mouse， 指定采集区域 -region\_border等参数。

例子：

1)录制桌面

ffmpeg -f x11grab -framerate 25 -video\_size 1366\*768 -i :0.0 out.mp4

图像的分辨率，以实际电脑的支持来，我的因为是1366\*768，所刚好录制下整个屏幕

我设置的参数为： 帧率为25帧 ，分辨率为 1366\*768，采集设备为 0.0，输出的文件为out.mp4

2)带鼠标的录制桌面

ffmpeg -f x11grab -framerate 25 -video\_size 1366\*768 -follow\_mouse 1 -i :0.0 out.mp4

3)指定录制区域

ffmpeg -f x11grab -framerate 25 -video\_size 352\*288 -i :0.0+300,200 out4.mp4

\-i :0.0+300,200 制定了x坐标为300 y坐标为200

这样就可以录制桌面了。

帧率ffmepg 摄像头_ffmpeg录屏/录音/录摄像头----命令行实现

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