[indent]“Failed to render a sample. Error: Windows DirectShow Audio: no decoder can handle the given audio file, or decoding failed (Internal Error: ‘Unable to determine duration of the audio stream.’).”[/indent]
This only broke for me? Windows, obviously.
Was this a former dynamic (variable bitrate) encoded Mp3? The Windows decoder is not capable of correctly calculating the complete time of these mp3 files.
If you in this case submit the sample as a constant bitrate mp3 or you simply decode it to WAV prior to loading into Renoise, i suspect the problem is over.
I would vote for Renoise to translate the complete mp3 to WAV and does an internal recalculation of the sample-size / time itself rather than relying on Windows decoder.
it was flac files. (but i don’t know what it was before that)
Sharing the xrni instrument might shed some light on the problem for the developers.
Wait wait wait… you mean it doesn’t do this already? 
I don’t know, i always assumed it did, it looks like it doesn’t or not in all cases.