Suggestion: Ability to have an IQ buffer and ability to scroll waterfall through buffer to re-play events

[khaytsus]

I'd love to see GQRX have the ability to stream the IQ buffer to a file to store the last N minutes of data to disk, and as it stores it removes old data so it would only use a fixed amount of disk space based on how many minutes to store and bandwidth of the SDR in use.

To use that buffer, GQRX could allow the user to scroll backwards through the waterfall to re-play a previous event. GQRX could probably have to stop showing the most recent data, but ideally continue to record into the buffer. This might cause the buffer to get larger than normal but maybe set a fixed 2x normal buffer size when in 'review' mode in which the data goes away in case the user goes into review and leaves it there. Or time out eventually and go back into normal mode.

It'd also be handy if the waterfall were timestamped to see that you're reviewing something from 5 minutes ago, etc.

The use cases are many, but you could review traffic on multiple channels that you missed while listening to another, re-play (and possibly record audio of) an event you just listened to, etc.

[diodelass]

I've been wanting this in some SDR suite for a long time. A decade or two ago, this would have been a hard sell, but now that computers have enough RAM to store many minutes of rolling buffer without much trouble (one minute of raw RTL-SDR stream takes up about 300 MB) I feel like it could very much be worth considering. At the moment, I do not know of any SDR frontend that can do this, which makes it frustrating to just barely miss something interesting on the air, and have no way to hear it, only stare at its image on the waterfall plot as it slowly slips away. Being able to save the current buffer would also make recording interesting signals dramatically easier, since you could save recordings of events that have already happened, without having to start up recording at the start of your session and deal with potentially many gigabytes of empty or sparse files later. This is a way that SDR could fairly easily be dramatically more powerful than conventional dedicated radio sets, and I'd love to see it in GQRX.