I'm using avconv/FFmpeg to parse a video feed and an audio feed into a broadcast stream. Currently, it gets its audio information via UDP with the options
-f wav -ac 1 -i udp://localhost:6613, since stdin is occupied with the video feed, and the audio is being processed by an external program before it gets sent to the local port.
Unfortunately, if the audio feed stops for any reason - the most common of which would be the user just turning off that feed - avconv just sits there and "blocks", waiting for more input on that channel, and it won't process any further video until it gets it.
The desired result is for the stream to just continue on without any audio, and then have audio again once that feed returns. I don't necessarily have to use UDP, either - if there's another way to receive a byte stream from another program on the same system, I can switch to that easily enough. I'd just rather not have to waste cycles sending a stream of 0's, and instead have that handled internally by avconv.