Faqs Faqs

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These are plain-speak technical FAQs, intended to help you understand media encoding and content streaming. As you know, this is a very broad and fast moving topic so if you have a question that we don’t answer here, please email us so that we can keep our FAQs fresh.

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Top 5 Most Asked Questions

Media encoding and streaming is new and changing fast. We at Sharpstream have to be at the forefront of all the new technologies, formats, devices and trends in order to provide the service our customers expect. This section of the website is designed to give you a flavour of what we're up to as well as some background information on the industry, the technology and what we consider best practice.

Q. Hardware vs software encoding – what’s best?

A.

The difference in quality between the two is negligible. What differences there are often relate to the operator’s preferences: a workstation will typically work in a familiar environment such as Window or MacOS; as with many IT systems, the computer may be upgradable for a certain degree of future-proofing as hardware improves and new codecs are launched; for operations with occasional encoding needs, the flexibility of running a multi-purpose workstation may be a tempting proposition.

The limitations of software encoding are also the limitations of being in a computer environment: workstations are not designed for continuous live encoding: background services or other applications may interrupt the encoding process with unforseen and unpredictable results. One of the key benefits of standalone hardware encoders then is task-focused reliability. Certain encoders have the advantage of being developed for specific conditions: some, for example, are manufactured for location encoding, when a cumbersome workstation would be impractical.

Q. What is Adaptive Bitrate?

A.

Adaptive bitrate (ABR) is one of the leading ways that video will be streamed over the Internet in the future. It detects the user’s (fluctuating) bandwidth and CPU ‘grunt’ in realtime and adjusts the quality of a video stream accordingly. ABR requires the encoder to encode the source content in to several files at multiple bit rates. Then, if necessary, the user’s player switches between streaming the different encodings if it can achieve a better result. While ABR reduces the likelihood of dropout for the viewer, it is an approach that requires the content owner to invest more heavily in advanced encoding systems, to insert keyframes every 10 seconds or so, to increase its data storage (for multiple versions) and to implement a compliant infrastructure.

Q. What is the difference between interlaced and progressive pictures?

A.

Most broadcast TV works with interlaced pictures all the way from the camera to the consumer’s screen. Most cameras record 50 fields per second where a field is half the height of a full frame. The two consecutive fields are intermixed to create a single frame. This is known as interlacing. One second of a programme therefore consists of 25 frames – or 50 interlaced images. Interlacing reduces the bandwidth (and storage space) by half, without losing vertical resolution.

While this sounds appealing, interlaced pictures can be problematic: when combined (de-interlaced) for display or streaming, two pictures are being blended that may have important differences between them – particularly in fast motion sequences. Blending the two fields together, depending on the method used, can result in a slight blur, jitter or a loss of resolution. It takes highly sophisticated algorithms such as motion adaptive blending to create a good look with highly complex motion pictures.

Progressive pictures do not suffer from the same limitation. In progressive mode, the full frame is captured rather than only one of two fields. However, because they capture full frames, they place a greater burden on the processor and result in larger files unless the screen resolution is reduced (usually to 720 rather than 1080 lines). The human eye also perceives that video shot at 25 frames per second can be jittery. For broadcasters, the nirvana is 50 or 60 frames (progressive) per second – and this is a realistic goal for the television industry.

Q. What’s the difference between a codec and a container?

A.

A container is the file wrapper – such as .avi, .mov, .mp4, etc. Codecs are the compression decompression algorithms that do the work. Although some containers have the same name as the codec (eg .mp4) this isn’t always true. An .mp4 file might have the x264 codec or the Main Concept h.264 codec.

Q. What does ‘muxing’ mean?

A.

Muxing/Demuxing is short for Multiplexing/Demultiplexing. Muxing is a process where separate parts of the video or “streams” are joined together into a single file. Demuxing is the reverse process where streams in a media file are separated into different parts. As an example, for television broadcasters, a video stream is multiplexed (muxed) with its audio tracks into a single file for delivery. For streaming, technicians may have to choose H.264 video muxed with either MP3 audio or AAC audio; in this instance, the decision may come down to licensing issues, or the need for surround sound.

Q. CBR Vs VBR: Help!

A.

As opposed to constant bitrate (CBR), Variable bitrate (VBR) files vary the amount of data throughput per second. VBR allows a higher bitrate to be allocated to the more complex segments of media files (such as action scenes or scenes with a complicated background) while less space is allocated to less complex segments (such as shots of a clear blue sky!). The average of these rates can be calculated to produce an average bitrate for the file. The result should be a more pleasing and faithful image.

While a VBR may sound the clever way to encode, for web delivery, a variable bitrate has distinct disadvantages: the bitrate, if unconstrained, may exceed the maximum data transfer speed of the web connection causing dropout or jitter. Equally, the encoding is a more complex, processor-intensive and therefore lengthy task. For a distribution network, delivering streams whose bitrates are ever-changing puts a heavy burden on its infrastructure: it may be difficult to cope with streams peaking simultaneously in terms of their bitrate; a constant bitrate is easier to manage and plan for.

Q. .WMV, .WebM, .FLV, .MP4, .MP3… how to decide?

A.

In general, it makes sense to encode media into the format that is most widely accepted by the intended audience. A PC-dominated audience may prefer Flash; sending video to a market sector that has embraced the iPad may need a different approach. The best advice is to survey the audience, review statistics from your CDN and analyse your website traffic. The final piece of the jigsaw is to gauge whether there are licence fees to be paid now or in the future for using a particular codec.

Q. What is WebM?

A.

WebM is a royalty-free, open video compression format for use with HTML5 video. It is a container used for VP8 video with Vorbis audio created by Google.

Q. Multi-pass encoding and single-pass encoding?

A.

Multi-pass encoding (usually 2-pass) is a method of ensuring the highest image quality at an optimal data-rate. In the first pass, the source material is analysed and the result is stored in a log file. In the second pass, the first pass information is used to achieve the best data rate and image quality. Because of the results multi-pass encoding delivers, it is routinely used in many sectors. However, the process is processor-heavy and time consuming so where speed is essential, it can be omitted.

Multi-pass encoding cannot be used in live broadcast or live streaming. It is used only for VBR encoding, because CBR encoding does not alter the bitrate.

Q. What is flash streaming and how does it work?

A.

Read our Flash Streaming PDF for more information.

Q. I’m new to podcasting. Do you have a “how to make a podcast guide”?

A.

You can download our how to make a podcast document.

Q. Why does my stream keep buffering all the time?

A.

This could be due to a problem with the encoder session or connection line between the encoder and our servers. Try creating a new encoding session and see the results. If this does not work, test your encoder on a different broadband line. It is common that your connection to the internet may be having troubles uploading the data at a constant rate. If you still have further troubles, please contact us.

Q. I have logged on to sawmill and I don’t understand it – can you explain this to me?

A.

Please download the sawmill user manual

Q. How many concurrent listeners do I need to start with?

A.

The thing to remember hereis that ‘concurrent listners’ does not mean ‘total number of listeners’. For example, if you have 50 listeners concurrently connected you can serve 1000’s of people in a week.

Q. Does it cost more for Stereo or Mono?

A.

No, however, it does depend on your bit rate as to how many listeners you have signed up for.

Q. I don’t understand routers; can you configure mine for me?

A.

We can fully support routers that we supply to you. For third party devices, your first port of call would be to your own technical department to ensure that you are in harmony with the guidelines laid down for your local network. Following that, please visit the manufactures website for instructions.

Q. What happens if I have too many listeners listening to my stream?

A.

It is not possible to have too many listeners listening to your Stream. When you first start your service with SharpStream, you are given an option of how many people at any one time you would like to be able to listen. If this appears to be at a maximum a lot of the time, you can easily upgrade.

Q. Can you set up the encoder for me?

A.

SharpStream to provide a encoder installation service. Please contact the sales team to discuss this by emailing sales@sharp-stream.com stating your enquiry.

Q. I have seen products like the Roku – can I use this to stream my audio or just to receive.

A.

The roku is a stand-alone Wi-Fi Internet Streaming receiver. It enables you to listen to Internet streaming without the need for a PC.

Q. I have SDSL – Can I stream?

A.

It is easily possible to stream over SDSL. It works in the same way in which standard streaming works.

Q. Do you offer Geo-Blocking?

A.

We do offer a Geo-Blocking service. Please enquire with our sales team.

Q. What is full load balancing?

A.

This is where more than one Streaming Server shares the workload of your Internet Streaming. The Php script that you are first given when you sign up to our services has all the server information. If a server was to crash or go off line, you will still be able to stream from the remaining servers. Any users that were connected to the Streaming Server that crashed will automatically be redirected to another server.

Q. Do SharpStream provide encoding computers?

A.

We do not provide encoding computers as standard with our service; however, we can offer these at point of sale. Please remember that all encoding computers do not come with technical support.

Q. How do I upload pod casts?

A.

As a Sharpstream account holder, you will be given FTP details. Using a standard FTP client you can upload podcasts or other media content to your area on our servers.

Q. I am unable to upload my files to the Storage Server

A.

This is likely to be due to running out of space on your folder. All folders are limited to the purchased storage amount. Try deleting some files, or if you want additional storage please contact sales@sharp-stream.com

Q. I can’t connect to the Storage Server.

A.

After verifying the settings you are using and the health of your own Internet connection, please contact us directly for assistance.

Q. How do I upload my content to your storage servers?

A.

As a Sharpstream account holder, you will be given FTP details. Using a standard FTP client you can upload podcasts or other media content to your area on our servers.

Q. How do I create an On-Demand File?

A.

Firstly, create a video or audio clip or programme as you would normally do. As far as possible, video content or audio podcasts should then be optimised for streaming. Your finished media can be of any length and size (depending on the bandwidth you have subscribed to). Firstly you should speak with us about the best format to encode in. Then, for video we would recommend that you set the bitrate at between 1000 kbps and 4000 kbps depending on the likely connection speed of your users.

Q. What is the difference between Live and On-Demand?

A.

Live Internet Streaming is pulled by Streaming Servers from the encoder and broadcast as the encoder receives the audio or video. Live Internet Streaming will only have one link to the content. On-Demand files are uploaded to a storage array, and played through an On-Demand point. These files will all have their own individual link on your website for people to listen to as and when they want.

Q. How will people listen or watch my channel?

A.

There are many ways in which that can do this. You can use an embedded web player in your website, or you can just have a listen now button on your website which opens their Media Player on the computer they are using.

Q. How much is Shoutcast Encoder?

A.

Shoutcast encoder is free. You can download this from here: http://www.shoutcast.com/download/broadcast.phtml

Q. What is the cost of Windows Media Encoder?

A.

Windows Media Encoder is free. It is downloadable here: http://www.microsoft.com/windows/windowsmedia/forpros/encoder/default.mspx

Q. Do I need my own Streaming Server?

A.

No, Sharp-Stream own many streaming servers in our London data centre that you will have use of when you purchase streaming through us.

Q. What is a Streaming Server?

A.

A streaming server connects to your encoding computer and pulls your stream once. This stream is then distributed to many end users by the streaming server. It manages connections to your Internet Stream and ensures the end user gets the best possible connection.

Q. How do I set up Shoutcast Encoder?

A.

Please see our Shoutcast Installation document.

Q. How do I set up Windows Media Encoder?

A.

Please see our Windows Media Encoder installation document.

Q. What type of computer do I need for encoding?

A.

The most practical solution to encoding is to use a Windows XP or Windows Vista Computer with your encoding software installed. Recommended hardware specifications are: – 2 GB free HDD space – 400Mhz processor or better – 512 MB RAM A general rule is the better computer you have for encoding, the lower the latency.

Q. What is the maximum bandwidth that I can use?

A.

This depends on the amount of listeners at a certain bit rate you have paid for. Our systems can handle anything up to 2 million connections at any one time.

Q. What is Bandwidth?

A.

Bandwidth is how much of the capacity of an Internet connection that you are using at any one time. For example, if you have 50 users connected to your Internet Stream at the same time, and they are listening at 32kbps you will be using 50 x 32 = 1.6kbps of bandwidth.

Q. What is a Bitrate?

A.

A bitrate is the quality of the audio or video that has been encoded. The higher the bit rate the better the quality.

Q. Can I Encode from anywhere?

A.

It is possible to encode content from almost anywhere in the world. You only need an Internet connection that is fast enough to upload the content and a source of audio or video. You can even encode using portable 3G cards available from Mobile Phone vendors. For more information on encoding a special events please contact sales@sharp-stream.com

Q. How fast does my Internet connection need to be to receive Internet Streaming?

A.

This depends on the Bit rate that the content has been encoded in. It is possible to listen to Internet Streams that have been encoded at a bit rate of 20kbps on a dial up connection. For Video that is being streamed it is usually recommended to have a 2mbps download connection. You can find out this from you ISP.

Q. How fast does my Internet connection need to be to upload a stream to your servers?

A.

We recommend that your Upload speed on your Internet connection is a minimum of 256kbps. This ensures you can take full advantage of our advanced load balancing features.

Q. What is the best encoder to use?

A.

Different types of encoders each have distinct advantages and disadvantages. Generally, the most prevalent method is to use Windows Media Encoding. To figure out which encoder is best for you, please contact a member of the sales team on sales@sharp-stream.com

Q. What is Shoutcast?

A.

Shoutcast is a program that takes the Audio or Video and converts this into a readable format for most Media Players. Shoutcast encodes content in an MP3 format.

Q. What is Darwin Encoder?

A.

Darwin Encoder is a program that takes the Audio or Video and converts this into a readable format for Real Player. Only Real Player can play this content after Darwin Encoder has encoded it.

Q. What is Flash Encoder?

A.

Flash Encoder is a program that takes the Audio or Video and converts this into a readable format for Flash Media Player. Only Flash Media Player can play this content after Flash Encoder has encoded it.

Q. What is Windows Media Encoder?

A.

Windows Media Encoder is a program that takes the Audio or Video and converts this into a readable format for Media Players. Windows Media Encoder encodes in a format called WMA. Windows Media Encoder is the most popular encoder for Internet Streaming.

Q. What is Buffering?

A.

Buffering helps you to listen to an internet stream without interruptions. Your media player will be sent the first few seconds of the Internet stream to temporarily store. This ensures if there is a gap in the connection between the streaming server and your PC, it will be able to catch up with itself without a gap in the stream.

Q. What different types of encoding are there?

A.

There are 4 main types of encoding for Internet streaming. These are: – Windows Media Encoder – Flash Encoder – Shoutcast – Darwin Encoder.

Q. Can I Encode from anywhere?

A.

It is possible to encode content from almost anywhere in the world.
You only need an Internet connection that is
fast enough to upload the content and a source of audio or video.
You can even encode using portable 3G cards
available from Mobile Phone vendors.
For more information on encoding a special
events please contact sales@sharp-stream.com

Q. How do I Port Forward on My Router?

A.

Port forwarding on routers is usually a very easy process. This process
is different for all routers.
To ensure you do this correctly, it is
recommended that you visit the manufactures website for instructions.

Q. What is Internet streaming?

A.

Internet streaming is where media such as audio or video is delivered to your computer without actually downloading the whole file before listening / watching the file. Instead, the file is sent to your computer as and when you want it.

Q. What is a port?

A.

All information that is transferred over the Internet goes through a port.
A port is a virtual doorway to get to the correct path.

Q. What is Port Forwarding?

A.

Port forwarding is the technique of taking information destined for a
specific port
and Computer and ‘forwarding’ them to a
different port and/or Computer.
You would generally need to setup port
forwarding on your router. For Internet streaming,
a firewall passes all incoming connections
for a particular port to a computer within the internal network.
During this process, the port value could be
remapped or sent to another destination within the network.
Also, you will need to adjust any firewalls
that may be in place to allow the stream to go out.

Q. What is a Fixed IP Address?

A.

IP addresses give your computer an address on the Internet or on
an internal network. A fixed IP address from your Internet Service Provider
or Network Administrator ensures your IP address will never change.
This will enable Internet Streaming Servers to be able to see your Encoder
at the same address all the time, even when you have to reconnect to the network.

Q. What is a Media Player?

A.

A Media Player is a program of your choice that enables you
to listen or watch files on the Internet and on your computer.
There are many different Media Players to choose from,
however the most popular Players are: –
Windows Media Player – QuickTime – Real Player – Winamp.

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