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Audio for Mobile Devices Two Perspectives On Mobile Audio Now that we have a good grounding in the audio technologies available for mobile devices, where do we go? I asked two composers of audio content for mobile devices, David Brenner of Motorola and Jeff Essex of audiosyncrasy (a sound design firm), to get their perspectives on how this technology is best applied in the marketplace. With all of the different formats out there (GM, GM Lite, SP-MIDI, DLS, XMF, SMAF, CMX, etc.), how does one decide what format(s) to support, and what formats to create content in? For David Brenner of Motorola, it basically comes down to scalable solutions and what is supported within the MMS specification. For example, SP-MIDI by its very design is a scalable solution for music synthesis in a 5-24 note profile and is in the MMS and 3G specs. SMAF is a proprietary, hardware-based solution from Yamaha. It doesn't comply with MMS messaging standards, and is supported predominantly only in Korea and Japan. GM Lite is not scalable. CMX is not supported in the MMS spec.
For Jeff Essex, it really doesn't matter to him. His clients tell him what they need. It could be based on the number of handsets out there, or what formats are supported where. But in the end, it's not his decision to make. As far as formats and standards within the industry are concerned, there are two important developments afoot. The first is an effort to standardize multimedia content delivery in the XMF format. This would mean that both MIDI and DLS resources could be easily bundled together. The second is that the MMA is in the process of defining a Mobile DLS specification that would prescribe synthesizer performance and make other recommendations for mobile devices. Once these two efforts are finalized and make it into the MMS spec, it would be a no-brainer for artists to publish their mobile content in XMF files for the widest distribution and exposure. Are there content creation tools for all these formats? Jeff Essex admitted that finding tools is a challenge. "MIDI tools abound, but there is not a lot of stuff out there for SP-MIDI yet," Essex said. "Beatnik has an editor that can perform an analysis of the number of simultaneous voices in a MIDI file, which can be useful when creating the MIP message for SP-MIDI files. They also have a MIP tool that will create the MIP message for you based on your own MIP settings. "Similarly, there is nothing currently available to create XMF files, though there are rumblings that some sequencer manufacturers are looking to make this happen for MIDI+WAV files, at least for file-sharing and compatibility purposes. "For SMAF, Yamaha has an FM design and audition tool for their format." Who is supplying the content for mobile devices today? Especially within the terminal providers, there are in-house folks (like David) that want to retain control of their own content. But there are also a number of third-party outfits (Tribal Brands, Moviso, audiosyncrasy) who are working in this area, with more developers getting in all the time. It will be interesting to see how many of these third-party providers the business will support. The licenses for tunes are typically negotiated by the third-party provider, or already negotiated by the client, and sold to service providers or terminal makers for installation and download. And to be MMS-compliant, content should generally be delivered in SP-MIDI format, with recommended access to a GM-compliant synth. Are there any trends or standardization efforts underway which would change or grow the pool of available content artists? "Definitely XMF," Brenner replied. "But the greatest limitations today for mobile devices are processing bandwidth, storage limitations inside the device and the high cost of large message transmission. These directly relate to the quality of sound and cost of the device. However, when memory costs come down, processing power goes up and the costs for downloading or receiving larger messages decrease, the majority of audio on mobile devices will become increasingly sample-based, either in MP3 or some other format. Then everyone with a sampler will become a potential ringtone mix specialist, from major recording artists on down to home studio enthusiasts." How is the customer served by the alphabet soup that is mobile audio today? "Since content delivery is tied to the service provider, the customer can only get what's offered by their wireless company," says Essex. "The customer is ignorant of it all. They go to the mobile web site and download their new tones and songs. It's transparent to them. All they know is they're charged to install new stuff." With such seemingly paltry resources and audio quality (small wavetables, tiny speakers and enclosures, reduced bit-depths and sample rates), why the big push for multimedia and audio on mobile devices/cell phones? Essex and Brenner both agree that it's already getting quite a bit better, and will continue to improve by pushing the envelope. "That's always been our job," says Essex, "whether it was CD-ROM ten years ago, the web seven years ago, or wireless today. Two years ago, you couldn't get a 16-voice capable phone in the US. Now they're commonplace." As more phones support existing authoring tools and standards, developers will have a much easier time building games and rich multimedia content. Furthermore, David adds, it sells. "It's what people want. People want it, so carriers want it, and terminal providers have to give it. For if we don't, someone else will." Where do you see mobile audio going in the future? There'll be lots more streamed content coming out. We'll still need wavetable synths and MIDI for ringtones and games, until phones have processing power to perform interactive control of digital audio. But as more XMF (MIDI + DLS) content becomes supported, anyone can sell to anyone else. This will only serve to increase pool of potential content providers. Other quality improvements for audio are also in the offing. For instance, being able to use your own headsets with any manufacturer's phone would be a huge plus. Handset makers aren't headphone specialists, so get out of that business, says David. Jeff believes stereo earbuds would also provide more immersive audio experiences. What, if anything, should someone be doing now to start working in the mobile audio space? "Be a proficient MIDI composer, and get familiar with SDKs for various phones," Brenner recommended. Jeff Essex went further. "At least get yourself a 16-voice phone, sign up with a decent provider and start experimenting with the tunes and games that are already available," he said. "The skills that you may have learned from previous technology business cycles (i.e. think small, and meet the platform on its own terms) will come in handy." It's clear that game developers creating content for mobile devices are having to cope with audio technology that is still in its nascent stages. Yet these devices contain a number of strengths and possibilities that you shouldn't ignore. The landscape of options out there can be daunting, but the future is here. Selected Links Sonify.org
SP-MIDI tutorial Beatnik
MIP tool Pointers
on how to prepare and encode audio and video files for playback on RealOne-enabled
mobile devices Tips
on creating mobile media from RealNetworks
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