UDP stream to VLC

[rcarsey1]

Ideally, I would like to play the stream without buffering delays, etc. which typically occur when rtl_airband encodes and sends to an Icecast server, which in turn sends to a player (usually with its own buffer).

I've been trying to use the new UDP stream feature and have rtl_airband send to a machine which uses VLC to pick it up and play it. Here seems to be VLC's raw options (the rawaud section)

https://wiki.videolan.org/VLC_command-line_help/

It would seem that this should work: (i verified that NFM was not compiled into my binary)

.\vlc --demux=rawaud --rawaud-channels=1 --rawaud-samplerate=8000 --rawaud-fourcc=fl32 udp://@:1234

Anyhow, if we can figure this out, I'd like to update the wiki because VLC is a staple amonst

[charlie-foxtrot]

I haven't used vlc but maybe you're missing an IP address in your UDP path (unless it magically uses localhost when nothing is set):

udp://[[<source address>]@[<bind address>][:<bind port>]]
                                 UDP stream sent by a streaming server

Also, it doesn't work how? Is the audio bad or no sound at all?

Perhaps use nc to verify you can get UDP data from the instance of rtl_airband and save it to a file, then use that file to verify you have the vlc parameters correct to play the audio, then use nc to vlc to verify the UDP input parameters are correct.

[steve1515]

@rcarsey1 Did you ever get this to work?

I'm trying the same thing on Windows VLC and I can't get it to work. I've confirmed that capturing the UDP traffic into a file and then playing that file works correctly, but VLC directly listening on a UDP socket never works.

Does anyone else know of another player that would work on Windows?

[steve1515]

I've done some more testing, but couldn't get VLC to work. I think there might be something wrong with how VLC receives UDP streams, but I'm not exactly sure. I ended up writing my own UDP audio receiver program using the C# NAudio library and it works perfectly with RTLSDR-Airband.

[Joe392]

Has anyone had success receiving UDP audio from rtl_airband using a Java based library, perhaps similar to the C# NAudio library? From what I have seen so far, Java does not natively support a 32 bit audio sample format. So far I hear 'static' using a simple Java program to receive the audio from rtl_airband.

[charlie-foxtrot]

Don't use Java, but if the format is an issue you can use nc to pick up the UDP stream then pipe to sox to do a format conversion. For an example see #272 (comment)

[steve1515]

In case anyone is still looking for an easy way to play the raw audio stream on Windows. I was able to get it to work with FFMpeg's FFPlay utility with the following command line:
ffplay.exe -nodisp -ac 1 -ar 16000 -analyzeduration 0 -probesize 32 -f f32le -i udp://0.0.0.0:1234

[jimrochny]

In the output section of your rtl_airband .conf file, what did you set dest_address = " "; to? Was there a wildcard so any client can connect?

[steve1515]

The dest_address is set to the PC's IP where I want the UDP stream sent to. You can't put in a wild card. With UDP you are basically sending to a specific host.