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Re: [Discuss-gnuradio] gr-atsc module transmit questions

From: Tom Rondeau
Subject: Re: [Discuss-gnuradio] gr-atsc module transmit questions
Date: Mon, 26 Sep 2011 08:56:28 -0400

On Sat, Sep 24, 2011 at 10:40 AM, Jay Jones <address@hidden> wrote:

I am relatively new to gnuradio block-level development and am working with the gr-atsc module. I am specifically interested in the transmit portion and have a few [likely elementary] questions:

1) From what I can see the transmit functionality is only implemented up to the atsc_field_sync_mux(), I don't see the symbol mapping or VSB modulation though I have read a few other posts that suggest it is there. The gnuradio 0.9 has GrAtscWeaverModHead and GrAtscWeaverModTail header files but maybe these did not get modified into gr 3.x.

Well, the atsc receive functionality hasn't worked properly for some time. It's been on my todo list for ages, but I haven't gotten there, yet, so if you are working on it and can fix it up, that would be great!

So having said that, no, I don't think all of the pieces to make an atsc transmitter are there, either. So I don't think you are wasting your time or far off track.
2) The atsc_field_sync_mux block is derived from gr_sync_block however it outputs more data fields than it consumes (by a factor of 313/312). Even though this seems to work, for my own benefit I re-did this as a gr_block but I am not sure if that is necessary; could someone shed some light on why gr_sync_block works (or appears to but doesn't)?

Thanks for your time, JJ

Yes, if the block is outputting 313 and consuming 312 items, then it's not a sync block, so it sounds like you are doing the right thing. Being off by that small amount will have an effect, but my guess is that it was minimal. Maybe a blip or overwriting a value or two here and there. So it was probably that the problem wasn't noticeable but present. 

Let us know how you're getting along with it.


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