I mean something that could record continuously like a soundcard's line-in port, but much faster, like at the speed of an oscilloscope. I have a Picoscope and it has 2 modes, streaming mode, and block mode. In streaming mode it can only go up to 1MSPS, but in block mode it can go up to something like 20MSPS. Unfortunately block mode doesn't capture multiple consecutive blocks because it waits for the next trigger, and even when using block mode using no trigger (freerunning) trigger method it needs to wait for the last trigger reset before it automatically fires its next trigger. This leaves a gap in the data.
There are also standalone digital oscilloscopes that exist with USB ports, but those ports are only for saving a screencap of the oscilloscope screen and transferring it to your PC. That's because an oscilloscope isn't really built for capturing large ammounts of a signal, streamed to your PC, but rather about only showing small sections of a waveform for analysis.
I need something with the constant streaming of a soundcard, but the wide bandwidth that most oscilloscopes can only use in block mode (like a sample rate of 20MSPS to 50MSPS), something that will generate up to 6 gigabytes per minute of data (assuming the data is 2 bytes per sample due to a ADC having a bitdepth greater than 8 bits per sample) on the harddrive, for the complete storage of the entire length of a several-MHz wide signal that can last several minutes in duration (the harddrive would be a dedicated 100GB harddrive or larger for capturing the signal, preferably a solidstate drive for fast writing speeds). This will allow further processing of that signal using software. Hopefully it will also have a better bitdepth than 8 bits per sample, like maybe 10, 12, or even 14 bits per sample (zero-padded to 16 bits per sample if its native bitdepth is less than 16 bits per sample, so that each sample will end on a byte boundary for easy processing using ordinary computer software).