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Streaming to Mobile Devices: Different perspectives on mobile content distribution

Streaming to mobile devices was one of the most talked about subjects at NAB’s Technologies For Worship Pavilion in 2010.

Now, with a new year ahead and several new mobile devices having entered the fray, including various tablet manifestations, streaming content to mobile is an even hotter topic.

That said, it is also a topic that raises many questions. We decided to throw some of the more prominent ones at some manufacturers who work in this realm every day, and an end user who has developed several solutions for houses of worship in the United States and abroad. The result is the following compilation of responses.

A look to the future
by Mike Nann

How are churches taking advantage of mobile streaming?

Most of our church customers who are deploying mobile streaming had already begun Web streaming of services, events and other content on their websites, and are expanding the reach of their message beyond web-connected PCs onto mobile devices.

Similar to streaming on the Web, mobile streaming allows churches to reach congregants unable to attend sermons in person. Members of your congregation who are traveling, for example, may be able to watch your live sermons from an airport, even without Internet access on their laptops.

Mobile streaming encompasses both live and on-demand content. While on-demand video allows repeated access to your content at your viewers’ preferred times, live streaming adds the element of immediacy that can deepen the connection between you and your viewers.

What are some of the unique complexities in encoding for mobile streaming?
One of the biggest considerations when encoding for mobile streaming is the diversity of technical requirements between mobile devices. There’s no single set of encoding parameters that can be viewed on all mobile devices. Each brand and model of mobile device may have different requirements for stream type, compression format, frame size and bitrate.

While the Apple iPhone (and its sibling devices such as the iPad) is the device most often thought of for mobile streaming, there’s a far greater breadth of mobile devices capable of viewing streaming video, and each has its own technical requirements.

When encoding for Web viewing, you don’t have to worry too much about things like different frame sizes, as PC-based video players are quite flexible and adaptable. And if the stream type you’re sending isn’t supported on a PC already, it’s usually a relatively simple matter for the viewer to add a new browser plug-in that will support it. It’s not that easy on mobile devices.

The core technologies supported by a device have a significant impact on their mobile streaming capabilities. Streaming to older mobile phones may require video streams based on 3GPP protocol specifications, which include both modern compression formats as well as legacy formats such as MPEG-4 Part 2 video and AMR audio.

Newer mobile devices share some commonality in compression format support – typically H.264 with AAC audio – but different mobile operating systems (such as iOS, Android and Windows Phone 7) use different delivery protocols. And even with a common underlying technology, devices may vary in display capabilities – even two phones from the same manufacturer running the same operating system may have different native display resolutions for video.
Attempting to provide device-optimized viewing experiences on a comprehensive range of mobile phones and devices might require providing close to a dozen different output streams.

What’s new in mobile streaming?
One of the key recent advances in mobile streaming is the introduction of adaptive streaming technologies. When streaming video to mobile devices, the unpredictable and frequently varying nature of the viewers’ bandwidth is a key challenge to ensuring consistent, high-quality viewing experiences.

Adaptive streaming technologies allow video streaming to automatically switch up and down between higher and lower-bitrate versions of the incoming stream as necessary to maximize video quality relative to the available bandwidth.
Thus, rather than a video stream choking up or failing when available bandwidth drops, the viewer simply receives a lower-bitrate (and thus lower-quality) version of the stream. A decrease in quality is much more preferable than a drop of the stream completely. HTTP Live Streaming for the iPhone brought adaptive streaming for mobile devices to the forefront, but adaptive bitrate delivery is also available or forthcoming on other mobile platforms from Android to Windows Phone 7.

From an encoding standpoint, the key is for the encoder to be able to create, with perfect synchronization, the multiple outputs at different bitrates for the streaming to switch between. Again, for an encoder that can already create multiple distinct outputs simultaneously, supporting adaptive streaming isn’t much of a stretch – likely a simple software upgrade is all that’s needed to add support for the specific adaptive streaming protocols commonly used.

Are separate encoders required for Web and mobile streaming?
That depends on the encoder you’re using, but with our (Digital Rapids’) encoders, Web and multiple variants of mobile streaming can be performed within the same encoder. Being able to stream to both the Web and mobile devices in a single encoder significantly reduces costs, technical deployment (such as routing source video signals) and operational effort.

Any thoughts on the future of mobile streaming?
Looking forward, the lines continue to blur between Web streaming to a PC and mobile content delivery, as the capabilities of today’s mobile devices continue to grow. Some of today’s smartphones offer more computing power than PCs did just half a decade ago, with robust Web browsing capabilities. The adaptive streaming capabilities mentioned earlier, for example, are available on both PCs and mobile devices, with both platforms using the same underlying technology. A few years from now (or sooner), we probably won’t be referring to “Web streaming” and “mobile streaming” any more – it will all simply be “video streaming”.

A Broadcast Perspective
by Ludovic Pertuisel

What are the main codec types used for mobile streaming?
At this point, the main Video codec for new devices is H.264. Old devices (more than 3/4 years old) only support H.263/MPEG-4 Part 2. As for Audio codecs: AMR-NB and HE-AAC v1.0 & v2.0 are two of the main ones.

Are there strengths and weaknesses associated with each codec?
The H.264 standard is the latest standardized codec. This standard uses additional tools (Deblocking, 1/4 pel) as compared to the older H.263 and MPEG-4 part 2. As a consequence it provides better encoding efficiency. Of course, the latest standard requires more processing power to encode and decode.

All the newest Mobile phones, and handsets support H.264 decoding. There are still a few requests for the H.263 and MPEG-4 Part 2 standard but only for compatibility with older devices.

What are the various format/aspect ratio changes that need to be made by a house of worship content provider to be able to stream to multiple devices?
Sending the same content to different devices involves sending the same content several times to be able to provide the best quality for each device. Consequently, the same content will need to be sent several times in different formats.

As an example, let’s say you want to send a TV channel to the following targets:
– Desktop computer
– iPad
– iPhone
– Other Mobile Phones

All of these devices have different technical features. For example, the screen of desktop computers or the iPad are bigger compared to the iPhone and other mobile phones.

For each target, you have a different video resolution, for instance:
– Desktops / iPad – VGA (640×480)
– iPhone (400×300)
– Mobile Phones (QVGA – 320×240 or QCIF 176×144)

Each of these devices can have access to different networks, for instance WiFi or 3G, and their bandwidth access can vary over time. So each video resolution must be proposed in different bitrates.

If you plan three different bitrates for each video resolution, you will have up to nine different profiles to encode for a single TV channel.

Are there file formats that work best with specific devices?
Yes, some devices such as the iPad/iPhone support “HTTP adaptive bitrate” from Apple (or HTTP live Streaming), the mobile phones should be compatible with the 3GPP standard.

For desktops, the Microsoft Smooth Streaming technology is also frequently requested.

The “HTTP adaptive bitrate” from Apple or “Microsoft Smooth Streaming technology” are called Adaptive Bitrate technologies.
When using such technology, the different profiles of the same TV channels will be encoded in several profiles at different bitrates and synchronized over time.

When running, the player will be able to calculate the available bandwidth and select the right profile on the fly without interruption on the video stream.

Let’s take a simple example:
A TV channel is encoded in VGA according to the Microsoft Silverlight technology in three different bitrates:
– 2 Mbps
– 1.5 Mbps
– 1Mbps

The maximum available bandwidth is 3Mbps.

What types of file conversion/editing/compression equipment is required to prepare content for mobile distribution?
For off-line preparation, you will need an off-line encoder. For a live event, you will need a product that will be able to encode all the different formats required (file formats, streaming, codecs etc.) in real time. In both cases, it is necessary to encode the files/live events into the different profiles for the different devices. (Desktops, iPhone etc.)

What are the differences in media conversion when comparing streaming to desktop computers versus mobile?
The video resolution, the bitrate and the streaming formats might be different, as described previously. Another important point is the profile used for compressing the video. In a video standard, there are usually several profiles, each of them use several tools described in the standard.

For instance, in H.264, the following profiles exist:
– Baseline Profile
– Main profile
– High Profile

The Baseline profile is used for mobile phones, as it is the least complex profile, requiring lower processing power. On mobile phones/handsets, battery life is key.

On a desktop computer, you can use the Main or Baseline profile since the processing power is less critical.

An End-User Perspective
by Marcus Singleton

As an end-user and speaker/trainer in the digital media industry, I have traveled to several different parts of the world and have experienced first-hand houses of worship in different technical and digital media environments.

For example, houses of worship in Africa struggle with inadequate bandwidth limitations, and not knowing what the requirements are for mobile streaming and desktop streaming. Also, the majority of HOW technical teams have one to three mobile devices per person (mobile devices are the preferred method of communication vs. landlines) overseas.

In effort to give a more “real world” picture of mobile streaming deployment in the house of worship market, and to provide a road map to getting started:

– Remember “Garbage In, Garbage Out”
Video and audio sources should be clean and free of noisy elements (pixilation and such) in the video. Audio should be mixed properly with no ground noise or low hum noises.

– Seek adequate bandwidth from your ISP (Internet Service Provider)
If you are streaming to mobile devices and desktop computers, be sure to calculate the bit rate you will be sending upstream to the CDN (Content Delivery Network). I usually recommend houses of worship to have a minimum of 1.5MB upstream and 1.5MB downstream (T1 bandwidth). Your budget will dictate how much you can spend on bandwidth connectivity each month from your ISP.

– Remember that your audience matters
Always think of the end-user first before you think of the media content you will stream to mobile devices. There are so many mobile devices on the market today. Knowing which mobile devices you will deploy is crucial to the workflow process of video production editing for VOD (Video On Demand) and for live broadcast production.

Your intended audience members know what mobile devices they have, and they know how they like watching and listening to content on their mobile devices. Conduct a small survey on your website and give something away for free for participating. Use this data to target the right formats (.mp4, .m4v, .m4a, .mp3, .3gp, .wmv, .wma, etc.) and protocols (http://, rtsp://, mms://, etc.) for those devices from the survey.

– Selecting the right CDN is also crucial to the deployment of mobile streams
Try several CDN’s and test their streaming infrastructure, server back-end, customer service, technical specifications and requirements, price per bandwidth (MB or GB), monthly or yearly pricing.

– Consider the role your Website plays in streaming
Is your website mobile friendly? Is it HTML 5 compliant? Are the URLs clickable and active for mobile streaming? Which method of deployment will you provide to the end-user? VOD (video on demand) or live?

I usually always recommend “walk before running”. If you have never deployed mobile streaming, start with VOD and then graduate to live broadcast, but only if live fits your model. This same method applies toward desktop/laptop streaming as well. If you are a “seasoned streamer” you could potentially go for both VOD and live.

– Last but definitely not least, select the right Encoder/Transcoder
Software/hardware media appliance will be determined by several factors (but not limited to the following):
• Price and Budget
• Scalability and Performance
• Technical Support and Functionality
• User Interface (GUI) and Flexibility
• Multiple Format Support
• Platform Support (mobile and desktop)
• CDN Support and Connectivity
• Archiving and Multiple Bitrate Processing
• Mobility or Stationary
• Ease of Use and Training Tutorials

As part of the TFWM Conference at InfoComm 2011, there will be seminars and workshops covering mobile streaming for houses of worship. Make sure to check for information on the seminar program and for additional content regarding mobile streaming applications,

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