EE 345S Real-Time Digital Signal Processing Laboratory - Lecture 8

Lecture

• Lecture on Quantization in PowerPoint format.

Supplemental Information

• Here are a few tradeoffs in sampling rate and resolution:
  NI PXI-5154 8 bits/sample at 2 GS/s sampling rate
  NI PXIe-5122 14 bits/sample at 100 MS/s sampling rate
  NI PXI-5192 16 bits/sample at 15 MS/s sampling rate
  NI PXI-5192 24 bits/sample at 500 kS/s sampling rate
• Mark A. Castellano, Todd Hiers, and Rebecca Ma, "TMS320C6000 mu-Law and A-Law Companding with Software or the McBSP", Texas Instruments Application Report, SPRA634, April 2000.
• The lecture discusses mu-law companding used in the US and Japan (u = 255) and A-law companding in Europe (A = 87.6). In the companding formulas, the log is the natural logarithm.
• A student asked what happens when a call is placed from the US to Europe. Companding in telephony is to eight bits, with one bit for the sign. Hence, the formulas in terms of |x| in [0, 1] would be used to generate a seven-bit number. To the precision of seven bits, there is no difference between A-law companding (A = 87.6) and mu-law companding (u = 255) for |x| in [0.18, 1].
• There is a mu-law pulse coded modulation (PCM) audio format. The format is an eight-bit floating-point format: 1 bit for the sign, 4 bits for the mantissa, and 3 bits for the exponent. This is a common audio format on Sun workstations.

Last updated 11/22/09. Send comments to bevans@ece.utexas.edu