This is from rockbox.org on fixes for the iRiver that they're working on:
Questions regarding recording with Rockbox (on the iRiver)
When will recording be implemented?
Recording is partially implemented in the current developmental version of Rockbox for the iriver H1xx series. However, at this stage, recording is still experimental and lacks several important features. For example, the recording function always uses the same filename; thus, if you make a recording, and then make a second recording, the second recording will overwrite the first. Likewise, the current implementation of the recording function cannot cope with long recordings.
The recording feature is currently in the Debug Menu. (Info --> Debug).
Will the recording glitch be fixed?
Yes, the recording feature in Rockbox will fix the infamous iriver recording glitch.
Will there be peak level meters for recording? And can I adjust input level on the fly?
Yes, and yes. These features have been implemented on the Archos Recorders for several years. All of the recording features that are currently available on the Archos Recorder should be supported on Iriver as well.
What formats will be supported for recording?
The first recording format will be uncompressed WAV. It is likely that recording to lossless Wavpack will follow. Unfortunately, it seems very unlikely that we'll have mp3 recording any time soon, due to the lack of an open source fixed point mp3 encoder.
Will recording in Rockbox have the same filesize limitations as the Iriver firmware?
No. The file size limit for recording in Rockbox will be 4 GB per file. (This is a limitation imposed by the FAT32 file system.) Thus, .WAV recording will allow a maximum of approximately 3 hours 20 minutes per file at 44.1 kHz 16 bit stereo (Being that the largest file in the FAT32 system is 4 Gigs - not 2 - I don't know if these numbers are still valid. They may need to be corrected). However, Rockbox has an automatic file split function, so it will continue recording in a new file.