The answer is, to a certain extent, subjective. MPEG compression is “lossy” – in other words, the decoded video does not look “exactly the same” as the original video. There is some loss of (hopefully not very important) information, as a trade-off for a higher compression ratio. Uncompressed standard definition video runs close to 300 Mb/s, while uncompressed high definition video runs close to 1.5 Gb/s. Using lossy compression, these bit rates can come down by a factor of 100 or more.
The encoder video bit rate represents a tradeoff between the video quality and the bandwidth required to transmit the video. In general, increasing the video bit rate increases the quality, but at some point the encoder gets to a region of diminishing returns, where increases in bit rate correspond to very small quality improvements.
The video quality is also a function of the complexity of the content. Simpler content, such as “head and shoulders” (for example, news) will require a lower bit rate than more complex content, such as sports and action movies. The final judge of whether it is “good enough” has to be a human being.
However, we can provide some guidelines. For Standard Definition video, the sweet spot is between 1 and 2 Mb/s. For High Definition video at 720p and 1080i, the sweet spot is between 6 and 8 Mb/s, and at 1080p it is between 10 and 16 Mb/s.
If you need to go to lower bit rates, there is another parameter that can be adjusted: reduce the horizontal resolution to ¾. On playback, all modern decoders will scale the signal back up to full screen. For SD, this means that the resolution will be 528x480 instead of 720x480; for HD, it means that it will be 1440x1080 (instead of 1920x1080) or 960x720 (instead of 1280x720). The image will be “softer”, but with less artifacts; the softness is typically preferable to the compression artifacts. Many broadcasters transmit SD at ¾ resolution.
AAC-LC and MPEG-1 Layer II are different types of audio encoding algorithms. In general, AAC-LC is somewhat better than MPEG-1 Layer II. “Better” means higher quality at the same bit rate, or lower bit rate for the same quality. However, most consumers will not be able to tell the difference between these two modes at bit rates 128 kb/s or higher.
The only scenario where AAC-LC is required is when streaming to some Apple devices, such as iPods and iPhones. Most IP set-top boxes and professional decoders will support both algorithms.
The short answer is that you should use a protocol that is compatible with your receiver and with your network. Here are a few guidelines:
NULL packets are “fillers” added to the MPEG stream to make it constant bit rate, with very precise timing. They contain no information.
Most professional decoders require the presence of NULL packets in order to recover precise clocks. Software decoders and IP set-top boxes do not need NULL packets, but will work with streams that include them.
The IP outputs in the EN460 default to including NULL packets because this is the most compatible format. If you are transmitting to IP set-top boxes or software decoders, you can turn off NULL packets and save a bit of bandwidth. If you use the HLS or Direct HTTP modes, the NULL packets are automatically suppressed by the encoder, as none of the target devices for these protocols require them.
Look at the source of the web page generated by the encoder and copy the block between these two tags:
Additionally, if you are using the Direct HTTP mode, find this line:
var hostval = 'http://' + window.location.host + ':XXXX/encoderY'
Where XXXX will be the port you configured in the encoder (e.g., 8000) and Y will be the encoder channel number (1 or 2), and replace window.location.host with the IP address of the desired encoder streaming port.
HTML5 indeed has the "VIDEO" tag, which supposedly allows compatible web browsers to natively play video on a web page. The problem, however, is that the standards community could not agree on exactly what format(s) the browsers were supposed to support. The result of this lack of agreement is that, even though all modern HTML5 browsers support the "VIDEO" tag, there is no single format that is supported by all browsers.
In most cases either a CDN or an origin server will be used to actually connect to the HTML 5 client. Since the formats required are either RTMP or Transport Stream and the EN460 encoders support both formats we do not see any problem in an application using HTML 5.
The way to play the video on a web page is through the use of the VLC plugin. In Windows machines, by default only the Internet Explorer plugin is installed; you will need to explicitly select the “Mozilla Plugin” for all the other browsers (Firefox, Safari, Chrome).
Depending on the configuration, the encoder will generate a web page with the appropriate plugin calls embedded. Point the browser at the IP address of the streaming port of the encoder, and follow the web page links. The encoder will generate video on a web page under the following settings:
Here is the procedure:
Now, configure the encoder to upload to the server you created (using the encoder username and password you defined above), and set the Base File Name to live. You can now use devices such as iPads to navigate to the page above, and when you click on the link, the video will open. IP set-top boxes can point directly to the “live.m3u” file.
The Roku player supports the HTTP Live Streaming (HLS) protocol for live, real-time content. In order to make the output of the encoder available to a Roku player, configure the encoder as follows:
In order to actually receive the stream in the Roku, you will need to create a channel for it. ImmediaTV has provided a general-purpose private test channel (adapted from one of Roku's sample channels) that allows you to specify the URL for the HLS stream. In order to add this channel, log in to your Roku account and use code RQQ2W to add this private channel (or use this link: https://owner.roku.com/add/RQQ2W). ImmediaTV may, at times, make available content from a test encoder accessible through the Internet; if you want to try this with your Roku player, please contact us.
In local server mode, the access URLs for the content are:
where xxx.xxx.xxx.xxx is the IP Address of the MVN-EN460 Ethernet port. Also note that if you use a browser to go to the encoder IP address, there will be a link for the HLS page.
These instructions apply to both the openGear MVN-EN460 and the modular ITV-EN460c. The ITV-EN460c can serve HLS streams over its control port, as well as the streaming ports.
Amsterdam, NL — Cobalt Digital today announced its acquisition of ImmediaTV, a Silicon Valley company
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