RTMP in the Age of HTTP Video Streaming: Don't Count it Out

Given the increasing popularity of and support for HTTP video streaming, it can be tempting to view Real Time Messaging Protocol (RTMP) streaming as antiquated. But there are several instances in which working with RTMP still makes a lot of sense. When Macromedia first introduced RTMP in 2002 with Flash Player 6, the brand-new Macromedia Flash Communication Server MX (FCS) was required to stream the nascent Flash Video (FLV) format, 无论是直播还是视频点播.

然而, FCS的许可费用很高(高达5美元),000 per server) and as a result CDN costs were high compared to other proprietary streaming formats. Some producers in the industry referred to the cost of RTMP streaming as the “Flash tax.” But Flash Player was near-ubiquitous on desktop browsers for well over a decade, 具有比其他插件更大的采用率. 流媒体服务器技术, 虽然, has historically been more difficult for web developers to implement, and simpler HTTP delivery has generally been easier and more cost-effective to deploy. In 2003, Macromedia enabled Flash Player 7 to support HTTP delivery of FLV files, allowing integrators to use standard web server technology for their online video deployment.

So, 在很多方面, RTMP as a VOD delivery transport hasn’t been a requirement for web video for more than a decade. 作为视频解决方案架构师, I look to business requirements as the driver for the majority of sound video decisions. And, even in 2014, RTMP is the de facto standard for the following use cases:

发布来自软件/硬件编码器的直播流: Nearly every streaming device supports RTMP to publish to CDN providers and streaming servers. Some native mobile apps even use RTMP libraries to publish a mobile camera’s live video.

即时寻求信息/回放: One of the benefits of RTMP streaming is its “enhanced seek” capability. 使用实时流传输, a player can seek to any point in the video with less buffering than HTTP delivery. 然而, you need Flash Player on the desktop to enjoy this feature, 因此, 这在移动浏览器上是不支持的. HTML5 browsers use HTTP range requests to facilitate faster seek for VOD files.

内容保护: RTMP can facilitate varying levels of content protection, from obfuscation to true DRM. For desktop browser playback, the browser does not cache RTMP streams.

自适应流媒体: One of my preferred uses of RTMP is adaptive streaming playback, wherein multiple bitrates and resolutions of content are provided to a video player, enabling the best resolution to play given current network speeds. 某些HTTP自适应流技术, 如HLS和MPEG-DASH, 实现类似的交付, but RTMP can be more responsive with respect to switching from one bitrate to another. 不幸的是, there is no standard for HTTP adaptive streaming across browsers that support HTML5 video. 像这样, Flash-based rendering of adaptive streaming still remains a requirement for adaptive streaming.

直播回放: 而直播不需要自适应, the same principle of packetized video segments applies to any live stream playback. Nearly all live streaming events for in-browser desktop playback require a video player that supports Flash-based rendering and RTMP playback. Apple Safari on iOS natively supports HLS, and fortunately, all modern streaming servers, including Wowza 流引擎，支持RTMP和HLS打包. The requirement for Flash Player with live streaming will only change when MPEG-DASH becomes as ubiquitous as Flash is today. 如果是Internet Explorer 8, 9, and 10 support is required for your live streaming deployment, RTMP流仍然是必需的. 也, 如果您需要在直播流上接近零延迟, HTTP streaming will almost certainly not meet your needs while RTMP can; HTTP mechanisms require more packets to accumulate on the server before sending them to the video player.

总之, if your video workflow involves live streaming or any packetized video deployment, RTMP is a key component to the success of the video experience. HTTP delivery has already replaced most Flash-based VOD deployment of video, but HTTP-based video cannot service all of the uses cases of RTMP-based video.

This article appears in the November/December 2014 issue of 流媒体杂志 作为“HTTP流时代的RTMP”."