No sound raw audio stream

[sea_hawk_12]

Hi,

I’ve been working on a project were I currently have the Raspberry Pi connected to a Cisco switch and receiving raw multicast data. It is audio data that is being sampled at 131,072 Hz. The size of each datagram being sent is 1407 bytes. I have written a piece of code to subscribe to the multicast group which works as expected.

My goal is to get audio out of the audio jack on the Raspberry Pi but I am having trouble doing so.
I have tried using VLC with various settings, but I don’t hear anything. I am starting to wonder if there is any documentation in regards to the on-board CODEC. I was unable to find any. I am also wondering if a 131,072 sample rate is way too fast for the Pi to handle. How would I go about down sampling incoming data?

I have Wireshark running on the Pi so I can see the multicast data being received by the Pi so that is not an issue.

Note: I have tested with playing an MP3 file over multicast, between two Raspberry Pi’s using VLC, and I am able to hear sound.

I am a bit lost on what next few steps I can take to troubleshoot this audio issue and any help will be greatly appreciated.

Thanks.

[topguy]

You kind of need to know the encoding of the data. Your sample rate is a bit bigger than the normal 44Khz, 48Khz, 96Khz etc. so maybe try to merge two samples to get 64Khz.

I dont know how you have tried to feed this data to VLC, but all programs needs to know how to interpret the data stream.
- Resolution ? 8 bit or 16 bit
- if resolution > 8 bit, is it big endian or little endian.
- Stereo or Mono ?
- Sample rate.

For PCM data in a Wav file for example the header of the Wav file will contain this information.

[sea_hawk_12]

Thanks for the tips. I will look into it, try some different things and get back to this topic.