Play file audio

Question

I have a raw data file of a sound recording, with each sample stored as a 16 bit short. I want to play this file through Redhawk.

I have a file_source_s connected to AudioSink like so:

I was expecting to hear sound from my speakers when starting these components. But when I start both components, I cannot hear any sound.

Here are the file_source_s properties values:

• filename: name
• itemsize: 2
• repeat: true
• seek: true
• seek_point: 0
• whence: SEEK_SET

I know:

• the problem is not AudioSink. I have tested the AudioSink with the signal generator (SigGen) and I could hear sound through my speakers.
• file_source_s is finding the file. When I put in a non-existent file name, file_source_s gives the "No such file or directory" error. I can also see the first 1024 bytes of the file when I plot the short_out port, but the plot does not update.

Answer 1

The AudioSink component uses the information from the received SRI (Signal Related Information) in order to determine the audio's sample rate. This is seen here from line 156 of the AudioSink component:

int sample_rate = static_cast<int>(rint(1.0/current_sri.xdelta));

It receives the SRI from downstream components, in this case, file_source_s.

The component file_source_s is part of the gnuhawk component package. The GNUHAWK library provides software that enables a GNU Radio block to be integrated into the REDHAWK software framework. Since SRI is a REDHAWK construct and not present in GNURADIO, it does not appear as though the file_source_s block gathers enough information via properties to represent the correct xdelta / sample rate for the audio file.

I'd recommend using a pure REDHAWK component like DataReader which takes in as a property the sample rate.