|Subject:||Re: [Discuss-gnuradio] Streaming Funcube Dongle Pro+ over UDP|
|Date:||Sat, 10 Aug 2013 03:47:41 +1000|
remove the gui sink. It also limits the sample processing speed and thus is equally bad as throttle.
Am 09.08.2013 19:33, schrieb Vanush Vaswani:
It doesn't help, I still consistently drop samples.
I tried increasing the buffer size in udp_source_impl.cc. I can record to .wav perfectly for about two minutes before the flow graph suddenly exits with (I'm assuming) a segfault.
For reference, I have attached images of the sender and receiver. Surely, this sort of streaming has been done before? I am using a BeagleBone Black running Ubuntu 12.04 (which runs fine - no overflows). The correctness of the FM receiver is less of a concern than the dropped samples.
On Sat, Aug 10, 2013 at 3:11 AM, Marcus Müller <address@hidden> wrote:
ok. Throttle does not _do anything_ with the samples. It just slows down the computational speed that they are processed with. Remove it, it breaks your flowgraph.
As said before, the WARN:... warnings stem from your UDP source. Data does not get processed fast enough; that's throttle's fault (before, the audio sink was limiting
your sample processing speed, which is in its nature).
Your flowgraphs are _not_ running at the same rate; they _may_ process samples at the same average rate (that's what throttle does, stop the sample flow when it's faster
than specified), but throttle does not convert sample rates.
Refer to existing Receiver flowgraphs from the internet on how to do things right, and please remember: 192kHz input MUST be downsampled for audio usage.
Have a nice day,
Ok, I still don't understand why I'm getting so many dropped packets.
FCDPP -> UDP Sink
UDP Src -> _Throttle_ (at 192KHz) -> WBFM Receive -> Wav File Sink
Note: no audio sinks.
I constantly get "WARN: Too much data; dropping packet."
Wave file is full of skips, yet both flowgraphs are running at the same rate?
On Fri, Aug 9, 2013 at 10:37 AM, Iain Young, G7III <address@hidden> wrote:
On 09/08/13 00:22, Vanush Vaswani wrote:You are always going to have to throw information away. You have 192k
If i add a rational resampler to match the audio rate before the UDP
sink, I can get a continuous output, but it's of terrible quality due to
the loss of information.
that you are trying to fit into human hearing, so you *must* filter
and then down sample.
How wide is your BPF/LPF ? Is it more than your soundcard can handle ?Your soundcard (probably) expects 44k1. The resampler takes care of
How does the flowgraph work having a sample rate 'mismatch' when the
FCDPP block is in the same graph?!
this, but of course, 192k is not going to go into 44k1. You need to
filter first.As I said before, google has plenty of examples of FM receivers with grc
Could you give me a hint in working around this issue?
(Google for gnuradio FM receiver grc, I'm sure you'll find loads)
Here are two working flowgraphs that start at 192k and 250k
They are actually a multimode receiver I wrote as an example for a
friend, and a multimode transceiver for ham radio use, but they show
the FM receive chain.
With both, you'll note I have a variable BPF so I can listen to
broadcast stations on MW/LW, and FM, SSB, or CW stations on the amateur
For pure FM you can drop the selector blocks, and just concentrate on
the NBFM receiver chain
Note if you need to be tuning with the FIR filter, you'll need to define
filter taps. I used a simple LPF.
Hope that helps
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