X-bit labs

Contemporary Integrated Sound Solutions: Storm is Coming (page 4)

Category: Multimedia

by Sergey Samarin

[ 08/25/2003 | 03:57 PM ]

Basic characteristics of VT1616:

• Six-channel DAC and stereo ADC with 18-bit definition;
• Variable sample rate with 1Hz stepping across all channels;
• Integrated IEC958 line amplifier for S/PDIF;
• Hardware down-mixing of multi-channel content to two channels;
• Stereo base enhancement for surround effects;
• Four stereo and two mono analog line outputs;
• Amplifier remote control circuit.

VIA VT1616 audio codec

VT1616 can process six audio channels at a time and with 18-bit definition. VIA specifies a SNR of 97dB for the codec, if it is used as a component of an add-in sound card (in this case, VT1616 is supposed to work together with the VIA Envy24 audio controller, which we have already discussed in detail in our previous articles). In the “noisy” environment of the mainboard, the SNR reaches only 90dB (although it is quite good for a low-end codec). To make the signal purer and reduce the heat dissipation, VT1616 doesn’t include a headphones amplifier. This allowed VIA marketing people to call this architecture “CoolAmp”.

Simplified flow-chart for VIA VT1616 audio codec

VT1616 can perform hardware channel down-mixing, thus taking this workload from the CPU. Again, marketing people at VIA don’t play lazy and invent names for everything. I checked this out: this technology is called DualMax (humble, and rather vague). In simple words, DualMax is a volume sound technology: multi-channel content is virtualized to be sent to headphones or a pair of speakers, which is important for a gamer, in the first place. It should be acknowledged that this function is implemented on the software level in most standard audio codecs. The manufacturer claims that the hardware approach is better: the sound is purer and more saturated, and not at the expense of quality. Moreover, VIA vows the mainboards with VT1616 can produce a higher-quality sound than those with nForce2 and mass codecs. They don’t say explicitly what mass codecs they mean, but it must be Realtek ALC650, I assume.

NVIDIA’s Way: To the Integrated APU!

Although the CPU took up nearly all sound processing tasks with the advent of integrated audio, they never stopped working on an auxiliary sound processor. It’s all because the CPU turned to be not fast enough for such tasks as encoding Dolby Digital streams, three-dimensional sound positioning with mathematics-heavy algorithms and so on. It was especially evident during DVD playback. NVIDIA was quick to come up with a solution: an audio processor unit (APU), integrated into the South Bridge of the nForce chipset. For today, NVIDIA’s APU is a worthy rival to the Creative Audigy2 sound card and even surpasses it in some functions.

NVIDIA’s supply met the demand from Microsoft. The corporation chose nForce APU for its X-box console. It’s not just good luck, since the sound processor has a powerful hardware part and supports numerous software interfaces used in modern games: DirectSound, DS3D, EAX 1.0 and 2.0, I3DL2, ASIO and OpenAL. As you see, only EAX 3.0 (EAX Advanced HD) support is missing, but this proprietary API is only available for the Audigy2 card today.