John Phillips wrote:
In article , Frank Johnson wrote:

For all the national services, the programme chain at the transmitter
site is:
Energis fibre or Microwave link feed, 8.448Mb/sec
Demultiplers down to 4x 2048 kbit/sec
"RE" electronics NICAM decoder, each national service has a bitrate of
676Kbit/sec for the stereo pair.


I presume that's 640 kbit/s for two channels of 10 bit samples at 32
ksample/s plus some overhead. (IIRC, NICAM encodes the original 14 bit
samples at 32 kbit/s down to 10 bits.)

Correct. Seems wasteful when compared to mp3 doesn't it?
Overhead such as range codes, framing etc..

If so, as has been pointed out, it's interesting to note just how good
FM stereo broadcasts of live events can sound.

Don't forget that the subjective effects of a small ammount of noise has
been shown to give an "aparent" improvement to ambience and seperation.
This is especially important as far as R3 is concerend because they use
the least compression so a lot of programme material is at low level.



The overall coding seems different from the 728 kbit/s stream that I
think is used for the rather versatile TV NICAM streams (according to
EN 300 163). I guess it's different to get three stereo channels into
2048 kbit/s.
Coding is the same but in TV, the clock has to be locked to TV Line
frequency as the data is carried by Dual channel sound in syncs.



Frank