Consumer or Professional Camcorders?
Professional and "prosumer" cameras allow you to control the image from each camera. Without such control, color and contrast may change unacceptably when you switch between cameras. But unless you have the eye and the training to detect and correct such differences, you will find that today's consumer camcorders produce remarkably good images for most purposes.
Pro cameras may include SDI outputs, but an adapter can convert a consumer HDMI to SDI. SDI typically uses locking BNC cables, where HDMI, mini-HDMI, and micro-HDMI cables do not lock so may be accidentally disconnected.
Prerecorded Video Sources
Analog studios used tape recorders to feed "roll-ins" of prerecorded media. Today's studios use computers to play back digital media files, from full-motion video to scrolling titles, lower-thirds, 3D animations, and still graphics, which can be composited in multiple layers (downstream keys) on top of your basic live camera picture.
Step Two: A Video Mixer/Switcher
If you have more than one live video source, you will need to combine their signals with a video mixer. The mixer/switcher may be a dedicated piece of hardware, or software in a computer with multiple inputs and outputs.
Dedicated digital video switchers can be expensive and have a fixed number of inputs. Computer-based mixers are only limited by the number of video capture devices you can connect and the power of the computer (the CPU and bus speed).
Computer-based solutions also let you play back prerecorded media files for program titles, teases, bumps, credits, commercials, etc., in addition to your live sources. These can play from the same computer running your switcher and encoding software, but this may limit the quality of your video. It may be better to play media files from a connected second computer, depending on the power of your CPU (your CPU utilization should generally be kept below 50%)
Analog video switchers were supported by separate video monitors for the cameras, the program output, and a preview of the next "take." Digital video switchers can show multiple video sources, preview, and program on a single high-definition video monitor, usually called a multiview monitor.
Step Three: The Video Encoder
Once you have a program signal from your switcher, it must be encoded and wrapped in packets for transmission over the Internet. This is the task of the video encoder, which may be just one more job for your computer-based digital video studio, or it may need one more dedicated hardware device.
Small, lightweight encoders accept an HDMI (or SDI) input and output H.264-encoded video on an Ethernet connection. Some can transmit the encoded stream over a WiFi connection directly to a streaming service. Some of these can record the video to an SD card or a connected USB device. Some are so small that they mount on the camcorder cold shoe. In these cases, very small hardware chipsets are doing the encoding work instead of a PC.
Those chips are now so inexpensive that some camcorders now include H.264 encoding and a USB or wireless connection to a computer for uploading to a streaming service directly from the camera. Similarly, smartphone apps can encode the camera video and send it for streaming by wireless or even LTE cell phone connections.
Looking to the future of streaming, the new HEVC
(High Efficiency Video Coding) or H.265 standard promises to cut the bit rates for streaming video in half. But encoding HEVC may take up to ten times the CPU processing, so it may not be in live production tools for years, being primarily useful for encoding on-demand
video. Decoding HEVC may take two- to three-times the processing, so playback will need more powerful CPUs. Google's open-source VP9
is a free alternative new streaming video codec for HTML5 browsers.
Step Four: A Single-stream or Multiple Adaptive Streams?
Who will be watching your live stream? More important, what platforms will they be watching on? A high-definition stream that looks perfect on a 1080p television monitor will not play on a tablet. And a mobile stream that looks great on an iPhone will look terrible on the HDTV.
Some streaming services will allow you to encode and upload one HD stream and they will decode it and re-encode it for multiple viewing platforms. This is called cloud transcoding. Otherwise, your video encoder will have to provide multiple streams, which may overwhelm your computer capability and/or fill up your Internet connection.
|6-10 Mbps||2.5-5 Mbps||1.5-3 Mbps||.6-1 Mbps||.4-.6 Mbps||.3-.4 Mbps||.2-.3 Mbps
streaming server starts by sending out the lowest data rate stream. If that arrives properly, it moves up to the next data rate. When a stream fails to arrive, it falls back to the next lowest rate that sends back acknowledgement that all the data packets were received.
Step Five: A Turnkey Streaming Studio or Build-It-Yourself?
The hardware and software needed to build a live-streaming multi-camera production studio is fairly well known as can be seen by studying the most popular turnkey systems. The benefits of a turnkey system are that the manufacturer has assembled and tested the system and is prepared to back it with a guarantee and technical support. The money you save building it yourself may not save you much if you don't know where the gotchas are.
Many turnkey systems are built on a combination of Telestream Wirecast
software and Matrox VS4
or Blackmagic Design Decklink Quad
hardware is available in a 5.8 x 12.4 x 16.75," 15 lb. portable case with integrated 17" monitor and in 2U and 3U configurations with from 4 to 16 camera inputs. They generally are based on Blackmagic Design
NewTek TriCasters use proprietary hardware available in a number of configurations. The popular TriCaster 40, with component and composite inputs, is a 10.4"x8.5"x17.5," 19 lb. box that uses a separate monitor and keyboard. The TriCaster 410, with 4 SDI inputs, comes in a 2U rack-mount case, 19"x21.5"x3.5."
1 Beyond says their 5”x13.5”x9”high, 12 lb. (14 lb. w/ battery) StreamMachine
is the industry's smallest portable quad direct-to-disk Recorder and live broadcast streaming production solution. It is built with the Matrox VS4 quad HD-SDI card and runs Telestream Wirecast 5 software.
The makers of vMIx software
offer a PC-based portable system similar to Livestream Studio, but with 4K production from 8 HD or SDI inputs and built-in graphics generation.
Build Your Own System?
VidBlaster has a set of recommendations
for hardware to run their software. As of Spring 2014, typical recommendations are the Intel i7 (quad core or even six core), DDR3 1333MHz RAM, and Nvidia GeForce 210 graphics.
Step Six: A Video Streaming Service or Your Own Server?
There are several standards for live video streaming - Apple's HLS
(HTTP Live Streaming), Adobe's HDS
(HTTP Dynamic Streaming), Microsoft's Smooth Streaming
, and the new MPEG-DASH
(Dynamic Adaptive Streaming over HTTP). Different streaming services or content delivery networks (CDN) may have proprietary protocols. Apple's Technical Note TN224
gives one of the industry's more comprehensive introductions to a standard.
In the past, exactly which codec (compression/decompression) was used for video and for audio (and which encoding/decoding, which streaming protocol, RTMP, RTSP, etc.) was not easy to discover, as dozens of standards are now mixed and matched, e.g., Apple QT QuickTime mov, aac, Windows avi, wav, wma, wmv, asf, Adobe flv, swf (Flash), MPEG mpeg-1, mpeg-2, mpeg-4, mp1, mp2, mp3, mp4, open-source Ogg, OGM, vob, RM Real media, DivX, 3ivx, Xvid, mkv, m1v, m2v, mpg, mpv, mpa, DTS, Dolby digital DD 5.1 - AC3, aif, ram, and many more. The camcorder standard AVCHD (Advanced Video Codec - High Definition) and the older DV is used to encode a vast fraction of the video recorded today.
Today the dominant codec for live streaming is H.264 (MPEG-4 AVC)
or the powerful new open-source version x264
. H.264 is one of the video encoding standards for Blu-ray discs. It is used by leading streaming internet sources, such as videos from YouTube, the iTunes Store, Vimeo, web software such as the Adobe Flash Player and Microsoft Silverlight, and also HDTV broadcasts over terrestrial cable and satellites.
Which streaming server?
Which video player client?
There are several video/media players
, many optimized for the streaming standard at a service or server - Adobe's Flash, Apple's QuickTime, Microsoft's Silverlight (Windows Media Player), Real Player, the JW Player for Flash and HTML5, and several open-source players, e.g., the VLC Player from VideoLAN.
All media players are now being optimized for H.264 playback.
Step Seven: Content Delivery Networks