1. 背景
在SRS使用中实现视频录制功能。
2. 思路
方案1：实时方式
- 拍照：操作者点击拍照按钮，触发网络请求，后端收到请求后启动一个ffmpeg 命令行进行截图。
- 录像：操作者点击开始录像按钮，触发网络请求，后端收到请求后启动一个ffmpeg 命令行录像，待操作者点击结束录像按钮后录像完成。
- 方案优点：容易实现
- 方案缺点：操作和响应的延时，即点击按钮后，约有2-5秒延迟（网络响应时间 ffmpeg启动时间 ffmpeg打开流时间 ffmpeg拍照响应时间。 争议：看到的视频的当前播放内容（时间） != 点击按钮时间 != ffmpeg拍照时间
方案2：DVR录制后拍照和截取
- 前提：开启DVR功能，对每一个来自客户端发布的流都录制，并以时间分段成多个物理文件，然后就可以操作文件截图和截取视频了。
- 拍照：点击按钮获得点击时间，从已经完成的DVR文件中识别文件名（包含了时间），读取文件后按指定时间差值截图。
- 录像：获得 开始录制时间和结束录制时间。从已完成的DVR文件中识别文件名（包含了时间），读取文件截取时间段内的截图。
- 方案优点：相比较于 方案1，时间误差的延迟小。
- 方案缺点：依赖于DVR录制后的文件。需要考虑DVR临时录制文件的清理处置。
3. 实现
代码语言：javascript复制DVR 视频录制: SRS支持将RTMP流录制成FLV或MP4文件。下面的描述以FLV为例。
vhost your_vhost {
# DVR RTMP stream to file,
# start to record to file when encoder publish,
# reap flv/mp4 according by specified dvr_plan.
dvr {
# whether enabled dvr features
# default: off
enabled on;
# the filter for dvr to apply to.
# all, dvr all streams of all apps.
# <app>/<stream>, apply to specified stream of app.
# for example, to dvr the following two streams:
# live/stream1 live/stream2
# default: all
dvr_apply all;
# the dvr plan. canbe:
# session reap flv/mp4 when session end(unpublish).
# segment reap flv/mp4 when flv duration exceed the specified dvr_duration.
# @remark The plan append is removed in SRS3 , for it's no use.
# default: session
dvr_plan session;
# the dvr output path, *.flv or *.mp4.
# we supports some variables to generate the filename.
# [vhost], the vhost of stream.
# [app], the app of stream.
# [stream], the stream name of stream.
# [2006], replace this const to current year.
# [01], replace this const to current month.
# [02], replace this const to current date.
# [15], replace this const to current hour.
# [04], replace this const to current minute.
# [05], replace this const to current second.
# [999], replace this const to current millisecond.
# [timestamp],replace this const to current UNIX timestamp in ms.
# @remark we use golang time format "2006-01-02 15:04:05.999" as "[2006]-[01]-[02]_[15].[04].[05]_[999]"
# for example, for url rtmp://ossrs.net/live/livestream and time 2015-01-03 10:57:30.776
# 1. No variables, the rule of SRS1.0(auto add [stream].[timestamp].flv as filename):
# dvr_path ./objs/nginx/html;
# =>
# dvr_path ./objs/nginx/html/live/livestream.1420254068776.flv;
# 2. Use stream and date as dir name, time as filename:
# dvr_path /data/[vhost]/[app]/[stream]/[2006]/[01]/[02]/[15].[04].[05].[999].flv;
# =>
# dvr_path /data/ossrs.net/live/livestream/2015/01/03/10.57.30.776.flv;
# 3. Use stream and year/month as dir name, date and time as filename:
# dvr_path /data/[vhost]/[app]/[stream]/[2006]/[01]/[02]-[15].[04].[05].[999].flv;
# =>
# dvr_path /data/ossrs.net/live/livestream/2015/01/03-10.57.30.776.flv;
# 4. Use vhost/app and year/month as dir name, stream/date/time as filename:
# dvr_path /data/[vhost]/[app]/[2006]/[01]/[stream]-[02]-[15].[04].[05].[999].flv;
# =>
# dvr_path /data/ossrs.net/live/2015/01/livestream-03-10.57.30.776.flv;
# 5. DVR to mp4:
# dvr_path ./objs/nginx/html/[app]/[stream].[timestamp].mp4;
# =>
# dvr_path ./objs/nginx/html/live/livestream.1420254068776.mp4;
# @see https://github.com/ossrs/srs/wiki/v3_CN_DVR#custom-path
# @see https://github.com/ossrs/srs/wiki/v3_CN_DVR#custom-path
# segment,session apply it.
# default: ./objs/nginx/html/[app]/[stream].[timestamp].flv
dvr_path ./objs/nginx/html/[app]/[stream].[timestamp].flv;
# the duration for dvr file, reap if exceed, in seconds.
# segment apply it.
# session,append ignore.
# default: 30
dvr_duration 30;
# whether wait keyframe to reap segment,
# if off, reap segment when duration exceed the dvr_duration,
# if on, reap segment when duration exceed and got keyframe.
# segment apply it.
# session,append ignore.
# default: on
dvr_wait_keyframe on;
# about the stream monotonically increasing:
# 1. video timestamp is monotonically increasing,
# 2. audio timestamp is monotonically increasing,
# 3. video and audio timestamp is interleaved monotonically increasing.
# it's specified by RTMP specification, @see 3. Byte Order, Alignment, and Time Format
# however, some encoder cannot provides this feature, please set this to off to ignore time jitter.
# the time jitter algorithm:
# 1. full, to ensure stream start at zero, and ensure stream monotonically increasing.
# 2. zero, only ensure stream start at zero, ignore timestamp jitter.
# 3. off, disable the time jitter algorithm, like atc.
# apply for all dvr plan.
# default: full
time_jitter full;
# on_dvr, never config in here, should config in http_hooks.
# for the dvr http callback, @see http_hooks.on_dvr of vhost hooks.callback.srs.com
# @read https://github.com/ossrs/srs/wiki/v3_CN_DVR#http-callback
# @read https://github.com/ossrs/srs/wiki/v3_CN_DVR#http-callback
}
}仍需要配置 HTTP回调
代码语言：javascript复制vhost your_vhost {
dvr {
enabled on;
dvr_path ./objs/nginx/html/[app]/[stream]/[2006]/[01]/[02]/[15].[04].[05].[999].flv;
dvr_plan segment;
dvr_duration 30;
dvr_wait_keyframe on;
}
http_hooks {
enabled on;
on_dvr http://127.0.0.1:8085/api/v1/dvrs;
}
}通过 HTTP回调将收到录制后的文件路径
[2015-01-03 15:25:48][trace] post to dvrs, req={"action":"on_dvr","client_id":108,"ip":"127.0.0.1","vhost":"__defaultVhost__","app":"live","stream":"livestream","cwd":"/home/winlin/git/srs/trunk","file":"./objs/nginx/html/live/livestream/2015/1/3/15.25.18.442.flv"}4. 参考
https://gitee.com/winlinvip/srs.oschina/wikis/v3_CN_DVR?sort_id=1701916
