Two basic questions

is recording from the sound card lossless? i don’t even know if i’m using the right terminology, since i’m new to this whole process, but basically what i want to do is record music from a web page; say, a java applet. i was able to do this successfully by choosing “stereo mix” in the drop down menu, and then simply hitting record. i then exported the file as a .wav. my question is, is any data lost in this recording process? in other words, after i export the file, would it sound any worse than the original file from the applet? i tried and i can’t really tell the difference, but i’m sure if i were to record the music by putting a microphone to another source, some quality would be lost. how about in my case? does it capture exactly what the sound card is playing perfectly?

also, is there a way to determine which parts of a music track are identical? suppose you have an exactly 1 minute long track that loops over and over again, but you are not sure when you record the track whether at at 61 seconds and 65 seconds, the sound is identical to 1 and 5 seconds. i want to tell audacity to compare the segment from second 00:01 to 00:05 with the segment from 01:01 to 01:05. is there a way to do this? i tried doing it with beat finder, but it returned nothing, so beat finder must be used for something else. sure, it sounds as if a 1 minute track is looping over and over again, but it could also be that 00:01 to 01:00 sounds similar to 1:01 to 2:00. i’m sure a computer would be much better at determining whether the first minute is identical to the second minute than my human ear. if the music truly loops, then i only need to record the first minute.

any help is appreciated. thanks!

Usually no, but if everything is set up correctly then it should be very nearly lossless. Mostly poor quality recording from Stereo Mix is due to having recording inputs enabled in the Windows Mixer for inputs that are not being used; for example, having the microphone “live” and not muted, which then means that you will be recording noise from the microphone input, even iof there is no microphone connected.

Re. Looping:

Select an area that includes a full “loop length” plus a bit more on each side.
Use Ctrl+D to make a duplicate of the selected region.
Use the “Time Shift Tool” (looks like a double headed arrow) to slide the duplicate clip left/right and see if you can get it to match up exactly with a different instance of the "loop"on the original track.
If you have a wheel mouse, use Ctrl+wheel to zoom in/out to help you position the clip accurately. If you don’t have a wheel mouse, use the zoom buttons in Audacity (they have icons of magnifying glasses).