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Re: [Discuss-gnuradio] Re: ATSC decoding - Now Working!

From: Bryce Kahle
Subject: Re: [Discuss-gnuradio] Re: ATSC decoding - Now Working!
Date: Wed, 27 Oct 2010 23:41:49 -0500

So after several sessions of comparing new code to old code, I found the problem. The root raised cosine filter was not being inserted into the graph before the fpll. The patch is pasted below. I successfully watched some video received from a local station (KFXL). I didn't get any audio, but I only captured for a couple seconds so I'm not sure if that is related or not.

Now that decoding is working again, I would like to work on improving/optimizing it where I can. Anyone have any pointers for places they know are current bottlenecks?


--- a/gr-atsc/src/python/fpll.py
+++ b/gr-atsc/src/python/fpll.py
@@ -70,7 +70,7 @@ def main():
        out = gr.file_sink(gr.sizeof_float,"/tmp/atsc_pipe_3")
        # out = gr.file_sink(gr.sizeof_float,"/mnt/sata/atsc_data_float")
-        tb.connect(u, fpll, lp_filter)
+        tb.connect(u, rrc, fpll, lp_filter)
        tb.connect(lp_filter, iir)
        tb.connect(lp_filter, (remove_dc,0))
        tb.connect(iir, (remove_dc,1))

On Fri, Oct 22, 2010 at 5:00 PM, Tom Rondeau <address@hidden> wrote:
On Fri, Oct 22, 2010 at 11:33 AM, Bryce Kahle <address@hidden> wrote:
> Has anyone been able to get the ATSC receiver working end-to-end since it
> was ported from 0.9? I'm able to get field sync aways into a small capture
> file, but the resulting transport stream file is not playable in Totem (with
> Xine backend). Does anyone have suggestions for where to look? I'm new to
> Gnuradio, so I'm still getting a feel for the codebase. Also, is there a
> better media player I should be using for the TS files?
> Thanks,
> Bryce Kahle

I've recently gotten about as far as you in working with it. I get the
field syncs fine, but the following decoding hasn't worked for me for
a long time. I have an interest in getting it back up and running
again, so please pass on anything more you can find out about it.


> On Sun, Oct 17, 2010 at 6:01 PM, Bryce Kahle <address@hidden> wrote:
>> I'm new to GNURadio and trying to get ATSC receiving going again. This
>> message is in response to the message
>> at: http://lists.gnu.org/archive/html/discuss-gnuradio/2010-07/msg00285.html
>> I believe the reason your 0.9 output is working beyond the bit timing loop
>> is because of a sampling rate difference between 0.9 and 3.X. 0.9 samples at
>> either 20MS/s or 21.52MS/s, while 3.X uses 19.2MS/s. The test files located
>> at http://comsec.com/data/README are sampled at 20MS/s. The reason it works
>> beyond the bit timing loop, with the output from 0.9, is because only
>> the interpolator, fpll, and bit timing loop (at least those are the ones
>> that I found an explicit reference to a sampling rate) care about the
>> sampling rate.
>> Thus you have proven that the field_sync_demux and beyond are working, but
>> anything before that is potentially at fault. I'm trying to narrow down the
>> issue, but haven't found anything yet.
>> Bryce Kahle
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