MPEG-DASH Industry Forum Releases Implementation Guidelines
The MPEG-DASH Industry Forum (DASH-IF) held a press conference today to discuss the release of DASH-IF implementation guidelines for the recently announced MPEG-DASH "limited edition" known as DASH-AVC/264.
Dr. Iraj Sodagar, DASH-IF president and chairman of the board, stated in an accompanying press release that the guidelines help with a crucial issue, interoperability.
“Facilitating complete interoperability is the key to achieving rapid market adoption of the MPEG-DASH standard,” wrote Sodagar. “The DASH-AVC/264 Implementation Guidelines offer companies a roadmap for developing interoperable products and services through real-world use cases from the multimedia streaming market.”
Interoperability for DASH-AVC/264 surrounds the use of the H.264 video codec, also known as the Advanced Video Codec (AVC). DASH-AVC/264 combines AVC with the AAC audio codec and the fragmented MP4 file format (also known as the ISO Base Media File Format).
Publication is expected on July 13, including about 25 test cases and a few real-world test scenarios for bitrate variation. Conformance software is also anticipated to be available around mid-July, along with several reference clients that are released under the BSD-3 license.
DASH-IF has defined test cases for interoperability points (IOPs) to implement conformance testing. One IOP that this site has covered, in terms of a DASH-AVC/264 client, is interoperability on adaptive streaming heuristics. The DASH-AVC/264 eliminates the need to interoperate for multiplexed media downloading, and also eliminates the need to interoperate with open group of pictures (GoP) switching, relying instead on closed GoP switching.
StreamingMedia.com has covered some of this news before, and one of the major surprises mentioned in a previous article was the limitation of DASH-AVC/264 interoperability playback to Main Profile version 3.1 or 720p30 content. Today, the DASH-IF announced work on a number enhancement, including 1080p, multi-channel audio, advanced codecs, and additional advertising services.
One questioner in the Q&A session asked about the use of Apple's HTTP Live Streaming (HLS).
"Apple was part of the standard process along with sixty other companies," said Sodagar. "We feel MPEG-DASH is a superior solution. If you look at the IETF drafts for HLS, there are multiple versions -- last time I checked it was up to 11 versions -- and it is a moving target.
"DASH as a standard was developed by the whole industry, not just a single vendor," he added.
"With HLS you have to request a manifest at the same frequency as you request fragmented segments," said Will Law, secretary of the DASH-IF, referring to the HLS manifest file also known as an M3U8. "This requirement to very frequently request the M3U8 may cause a resource issue when we move to large-scale HTTP-based live streaming."
"MPEG2 Transport Stream is designed for broadcast, but it doesn't inherently have the capability of a DVD-on-the-cloud", added Dr. Thomas Stockhammer, chairman of the Promotions Working Group of the DASH-IF. "To add extra functionality to HLS that's not part of the MPEG2 Transport Stream breaks compatibility with the core M2TS protocol."
Another audience question asked about Microsoft's support for DASH. The question was fielded by Sodagar, who works for Microsoft.
"What was announced yesterday at the Microsoft Build conference is the fact that Internet Explorer 11 will support Media Source Extensions and Encrypted Media Extensions," said Sodagar.
The use of Media Source Extensions (MSE) and Encrypted Media Extensions (EME) will allow browsers to support HTML5-based playback of DASH content. In addition to the announcement around IE11's support of EME and MSE, the DASH-IF team also noted that an upcoming version of Chrome will support EME.
The DASH-IF team announced that an initial publication of DASH-HEVC/265 recommendations will occur by July 13, 2013. The intent of this initial publication is to allow community review on suggested ways to integrate high-quality codecs such as High Efficiency Video Coding (HEVC) also known as H.265.
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