docker study

Author: jiangwh

audiocompress/ffmpeg.md

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+# ffmpeg
+
+最简单转码, 以mov转为mp4为例(支持绝大多数编/解码格式):
+
+```
+ffmpeg -i in.mov out.mp4
+```
+
+仅转码视频, 音频保持不变:
+
+```
+ffmpeg -i in.mov -c:a copy out.mp4
+```
+
+减小视频分辨率到720p, 码率为2500kbps, fps 30:
+
+```
+ffmpeg -i in.mov -vf scale=-2:720 -b:v 2500k -r 30 out.mp4
+```
+
+去掉音频:
+
+```
+ffmpeg -i in.mov -c:v copy -an out.mov
+```
+
+增大12dB音量:
+
+```
+ffmpeg -i in.mov -c copy -af volume=12dB out.mov
+```
+
+macOS使用显卡加速mpeg4转码(普通macbook应该只能使用这个, 独显可能支持更多驱动):
+
+```
+ffmpeg -i in.mov -c:v h264_videotoolbox out.mp4
+```
+
+录制在线视频流(示例将MPEG TS流视频不转码保存为ts文件, 源为m3u8列表文件):
+
+```
+ffmpeg -i http://xxx.com/yyy/zzz.m3u8 -c copy out.ts
+```
+
+录制在线视频流, 保存的同时转码:
+
+```
+ffmpeg -i https://xxx.yyy.flv?a=XXX&b=YYY -c:v h264_videotoolbox -vf scale=-2:720 -b:v 2500k out.mp4
+```
+
+截取视频中的一部分:
+
+```
+ffmpeg -ss 00:xx:yy -i in.mp4 -to 00:mm:nn -c copy -copyts out.mp4
+```
+
+-ss后面是起始时间戳, -to后面是结束时间戳, -copyts表示拷贝时间戳, 这会影响到音画同步. 在线视频流也支持从保存某个时间段的视频
+
+
+
+```bash
+# -aframes number     set the number of audio frames to output
+# -aq quality         set audio quality (codec-specific)
+# -ar rate            set audio sampling rate (in Hz)
+# -ac channels        set number of audio channels
+# -an                 disable audio
+# -acodec codec       force audio codec ('copy' to copy stream)
+# -vol volume         change audio volume (256=normal)
+# -af filter_graph    set audio filters
+ffmpeg -i out.mp3 -b:a 24K -acodec mp3 -ar 16000 -ac 1 out2Kz.mp3 
+# 声道转为1个
+ffmpeg -i out.mp3 -b:a 12K -acodec mp3 -ar 8000 -ac 1 out2z.mp3
+ffmpeg -i out.mp3 -b:a 24K -acodec wmav2 -ar 8000 -ac 1 out.wma
+```
+

docker/docker.md

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+# Docker
+
+## Namespace
+
+
+
+## Cgroup
+
+
+
+
+
+## UnionFS
+
+
+
+##code snapshot
+
+```go
+//overlay方式 挂载文件 
+//func Mount(source string, target string, fstype string, flags uintptr, data string) (err error)
+unix.Mount("none", "/var/run/gocker/containers/containerid/fs/mnt", "overlay", 0, "lowerdir=/var/lib/gocker/images,upperdir=,workdir=")
+
+```
+
+
+
+## net bridge
+
+```go
+	//利用go创建一个网桥
+	linkAttrs := netlink.NewLinkAttrs()
+	linkAttrs.Name = "bridge0"
+	gBridge := &netlink.Bridge{LinkAttrs: linkAttrs}
+	if err := netlink.LinkAdd(gBridge); err != nil {
+		return err
+	}
+	//设置子网掩码
+	addr, _ := netlink.ParseAddr("172.29.0.1/24") 
+	netlink.AddrAdd(gBridge, addr)
+	netlink.LinkSetUp(gBridge)
+```
+