版本：7.0 (Unstable) 🚧

DVR

SRS支持将RTMP流录制成FLV或MP4文件。下面的描述以FLV为例，但是对MP4也是一样的。

当 FFmpeg/OBS 将 RTMP 流发布到 SRS 时，SRS 将把流写入 FLV/MP4 文件。工作流程是：

+------------+            +-------+           +---------------+
+ FFmpeg/OBS +---RTMP-->--+  SRS  +---DVR-->--+ FLV/MP4 File  +
+------------+            +-------+           +---------------+

许多用户希望 DVR 提供更多功能，请考虑使用 Oryx 替代，例如：

Oryx 支持 S3 云存储，将最终的 MP4 文件移动到 S3 云存储。
Oryx 支持全局过滤器，仅记录指定的流，而不是所有流。
Oryx 支持将多个发布会话合并到一个 MP4 文件中。

实际上，DVR 功能可能非常复杂，SRS 只支持基本的 DVR 功能，而 Oryx 将继续改进 DVR 功能。

Build

DVR作为SRS3的核心功能，永远开启DVR。

参考：Build

Config

DVR的难点在于写入flv和文件命名，SRS的做法是随机生成文件名，用户可以使用http-callback方式，使用外部程序记录这个文件名，或者改成自己要的文件命名方式。

当然也可以修改SRS代码，这种做法不推荐，c操作文件名比较麻烦。还是用外部辅助系统做会很方便。

DVR的配置文件说明：

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://ossrs.net/lts/zh-cn/docs/v4/doc/dvr#custom-path
        # @see https://ossrs.net/lts/zh-cn/docs/v4/doc/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
        # @see https://ossrs.net/lts/zh-cn/docs/v4/doc/dvr#http-callback
        # @see https://ossrs.net/lts/zh-cn/docs/v4/doc/dvr#http-callback
    }
}

DVR的计划即决定什么时候关闭flv文件，打开新的flv文件，主要的录制计划包括：

session：按照session来关闭flv文件，即编码器停止推流时关闭flv，整个session录制为一个flv。
segment：按照时间分段录制，flv文件时长配置为dvr_duration和dvr_wait_keyframe。注意：若不按关键帧切flv（即dvr_wait_keyframe配置为off），所以会导致后面的flv启动时会花屏。
time_jitter: 时间戳抖动算法。full使用完全的时间戳矫正；zero只是保证从0开始；off不矫正时间戳。
dvr_path: 录制的路径，规则参考下一章。

参考conf/dvr.segment.conf和conf/dvr.session.conf配置实例。

Apply

DVR的apply决定了是否对某个流开启dvr，默认的all是对所有开启。这个功能是SRS实现nginx提供的control module的一个基础，而且更丰富。也就是可以支持用户调用http raw api控制是否以及何时DVR。参考351

Apply可以对多个流进行录制，譬如对live/stream1和live/stream2录制，可以配置成：

vhost xxx {
    dvr {
        dvr_apply live/stream1 live/stream2;
    }
}

可以使用RAW API控制DVR，参考319和wiki.

Custom Path

我们可以自定义DVR的路径和文件名，规则如下：

按年月日以及流信息生成子目录。便于做软链，或者避免一个目录的文件太多（貌似超过几万linux会支持不了）。
按日期和时间以及流信息生成文件名。便于搜索。
提供日期和时间，以及流信息的变量，以中括号代表变量。
保留目前的方式，按照时间戳生成文件名，保存在一个文件夹。若没有指定文件名（只指定了目录），则默认使用[stream].[timestamp].flv作为文件名，和目前保持一致。

关于日期和时间的变量，参考了GO的时间格式化字符串，譬如2006代表YYYY这种，比较方便：

2006-01-02 15:04:05.999

DVR支持的变量包括：

年：[2006]，将这个字符串替换为年份。
月：[01]，将这个字符串替换成月份。
日：[02]，将这个字符串替换成日期。
时：[15]，将这个字符串替换成小时。
分：[04]，将这个字符串替换成分。
秒：[05)，将这个字符串替换成秒。
毫秒：[999]，将这个字符串替换成毫秒。
时间戳：[timestamp]，将这个字符串替换成UNIX时间戳，单位是毫秒。
流相关变量，参考转码：[vhost], [app], [stream]

下面的例子说明了替换方式, url是rtmp://ossrs.net/live/livestream，time是2015-01-03 10:57:30.776

没有变量，SRS1.0方式（自动添加[stream].[timestamp].flv作为文件名）：
- dvr_path ./objs/nginx/html;
- =>
- dvr_path ./objs/nginx/html/live/livestream.1420254068776.flv;
按流和年月日分目录，时间作为文件名：
- 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;
按流和年月分目录，日和时间作为文件名：
- 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;
按vhost/app和年月分目录，流名称、日和时间作为文件名：
- 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;
按app分目录，流和时间戳作为文件名（SRS1.0方式）：
- dvr_path /data/[app]/[stream].[timestamp].flv;
- =>
- dvr_path /data/live/livestream.1420254068776.flv;

Http Callback

打开http_hooks的on_dvr配置：

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;
    }
}

api-server的日志：

[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"}
[2015-01-03 15:25:48][trace] srs 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
127.0.0.1 - - [03/Jan/2015:15:25:48] "POST /api/v1/dvrs HTTP/1.1" 200 1 "" "SRS(Simple RTMP Server)2.0.88"

更多HTTP回调的信息，请参考 HttpCallback

Bug

关于DVR的bug：

文件名规则：#179
DVR时HTTP回调：#274
DVR支持MP4格式：#738
如何录制成一个文件：#776

Reload

改变dvr配置后reload，会导致dvr重启，即关闭当前dvr文件后重新应用dvr配置。

Winlin 2015.1