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[Discuss-gnuradio] Hierarchical Blocks, New FM Deemph, GSM vocoder etc..

From: Eric Blossom
Subject: [Discuss-gnuradio] Hierarchical Blocks, New FM Deemph, GSM vocoder etc...
Date: Thu, 24 Feb 2005 16:22:57 -0800
User-agent: Mutt/1.5.6i

These's some cool new stuff in CVS.

You can now build hierarchical blocks out of primitives, hierarchical
blocks and random python code.  They are composable, and can be
connected up just like regular blocks. This gives us a good way to
start aggregating common functionality.

The wfm_rcv*.py examples have been refactored to take advantage of
this feature.  

I've also fixed the FM deemphasis filter and turned it into a block.
The new one computes the right answer (at least it looks right to me:
corner at about 2.1kHz, 20dB/decade slope) and WFM and NBFM sound better.

There's a new directory, gnuradio-core/src/python/gnuradio/blks
that will serve to collect these hierarchical blocks.

You access the fm_deemph like this:

from gnuradio import blks

   deemph = blks.fm_deemph(fg, sample_rate)

I'd appreciate it if one of you DSP guys would implement the FM
preemphasis filter.  The framework and some documentation are all
ready to go. See gnuradio-core/src/python/gnuradio/blks/fm_emph.py

Now that we've got hierarchical blocks, we can seriously start to work
on an abstract interface to the A/D's, D/A's and various RF front
ends, including the null front end.

There's also a new block (in its own CVS module: gr-gsm-fr-vocoder)
that wraps the 13kbit/sec GSM full rate vocoder (GSM 06.10).
When we get the FSK stuff sorted out, we can play with digital voice.

Stay tuned...


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