Program streams are what's on a DVD and in most MPEG files on your computer. The structure is designed for environments where the transport of the media from storage to playback is reliable and can handle variable-sized chunks of data.
Transport streams are what's used when the transport between storage and playback is not necessarily reliable and it's better to use fixed-sized chunks of data. The new digital TV broadcast standard is all about MPEG2. Cable TV uses transport streams too.
The technology is detailed and has a lot of complexity, but it's not, as they say, rocket science. There's some good summary information on the web but it's not really detailed enough to really understand the protocol. The actual standards documents cost hundreds of dollars and are great references but written as standards - not the easiest things to read to understand a protocol.
Thankfully there's a great book that explains transport streams in wonderful detail. It's called Data Broadcasting . You can preview and purchase it through this link:
The book covers transmitting data over the MPEG broadcast fabric. However, Chapter 2 of "Data Broadcasting" alone is worth the whole price of the book. It's a detailed explanation of the entire MPEG2 transport stream protocol. Every field is explained with commentary on why it exists and how it's used in the real world.
UPDATE - this book is apparently out of print now - only used books are available. That's a crying shame.
You'll have noticed that I didn't try to do a simple summarization repeat of the protocol. That's been done - google for it and you'll find it. True understanding a subject requires some time and effort. You can browse some web pages and get a shallow understanding of a topic - and that's a good thing. But if you really want to dig in and understand a technology the summary is not enough.
If you want to really understand MPEG2 transport streams, this book is a must have. This technology is foundational to a whole new set of great products we'll be seeing in the next few years. It's well worth spending the money and time to understand it.
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( 3 / 142 )SMIL is the acronym for "Synchronized Multimedia Integration Language" and it's pronounced "smile" by those in the know. SMIL is an Internet Standard XML-based language that is HTML-like. It's purpose is to enable the simple authoring of interactive audiovisual presentations. SMIL is for "rich media" presentations where there's a need to integrate streaming media with images and/or text.
In the past gathering information about SMIL required web searches and wading through a bunch of older pages, 'page not found' errors, or digging through the W3C reference pages and specifications. That's changed. There's now a fantastic book on SMIL 3.0 available.
This book has plentiful examples and explains SMIL in a clear and straightforward way. It's unusual in that it's in full color, which makes it much easier on the eyes.
Like HTML, SMIL controls the layout of the display - the spatial element of a presentation. HTML provides ways to do that - especially with CSS. Where SMIL shines is in the temporal control - the timing of video, graphics and text elements. SMIL provides ways to control the timing and synchronization of the media elements.
Adobe, Apple, RealNetworks, and Microsoft are all using at least parts of SMIL in their products - all around playlists and media playback control. SMIL is finding it's way into many products (like the Zune) as well. But one area that is really embracing SMIL is the field of Digital Signage. Several players in that space support now SMIL. For example, the Grass Valley/Canopus MediaEdge system and the IAdea XMP-300 both support SMIL. Premier Retail Networks (disclaimer: I work for them) operates one of the largest signage networks in the world and adopted SMIL as their playlist format several years ago. The POPAI Digital Signage Standards Group is considering SMIL as the basis for a common playlist specification.
SMIL is a foundational technology for tomorrow's media world. It's well worth learning about. The SMIL 3.0 book is a great way to get up to speed. I highly recommend it. This book is not cheap, but I promise you it will put a smile on your face about SMIL.
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