At 08:19 AM 9/2/2010, you wrote: >It's NOT a microphone issue. It's the small bit processing. I have >been in Pro sound for most of my life. Their is NO WAY to get any >quality at 8bit. This is unexceptionable to me! I rather listen to >all the QRM and QRN in the world with analog. >I am very surprise that their are not more people that feel this way. >The bit rate has to be at lest 28bit to starting sounding acceptable.
As others have pointed out, there is no simple way of relating speech vocoders to the sample size. This is quite a different ball game to pro audio. Different goals and different techniques. Also, you are mixing your terminology. Bit rate is measured in bits per second. Sample size (or sample depth) is measured in bits, which is what you appear to be referring to. For communications quality audio, you can use 8 bit sampling at 8 kHz (64kbps), but there will be an audible noise floor. You can go to 16 bit/8 kHz (128 kbps), which will result in flawless audio. Another option (as used in telephony) is to use 8 bit non linear sampling, (such as uLaw in the US), which gives a dynamic rage equivalent to 13 bit linear sampling, and a bitrate of 64 kbps. All these bitrates are considered too high for efficient voice communications, so then the vocoder's job is to use some strategy to throw as much away as possible, while keeping the audio intelligible. As the bit rate falls, the audio fidelity is going to decrease. From here, it's a compromise between bitrate (lower is better), fidelity and the amount of processing power and available algorithms. Of course, nothing's stopping you (possibly apart from cost/patent issues) from playing with something like AAC+ over higher speed ham links to get a higher quality digital system, though this is not the goal of most hams, who are more interested in communications capability than audio fidelity. There's always room in the hobby for niche interests, like hi fi radio (e.g. wideband AM or SSB on HF or WB FM on UHF). These are fascinating parts of the hobby in themselves. 73 de VK3JED / VK3IRL http://vkradio.com
