How to play a specific portion of an audio file with NAudio
Occasionally I get asked how to play an extract from an audio file with NAudio. There’s actually a class in NAudio that makes this very simple – OffsetSampleProvider.
OffsetSampleProvider allows you to skip over a specified duration from the start of the source audio (with a Skip property), and to only play a specified duration by using the Take property. So you could skip the first 30 seconds and then take then next 10 seconds for example. (OffsetSampleProvider can actually do a bit more than this – it can also insert silence at the start and end)
But just to show how simple it is to use, here’s a code snippet that takes a 10 second extract from an MP3 file, after skipping the first 15 seconds:
var file = new AudioFileReader("somefile.mp3");
var trimmed = new OffsetSampleProvider(file);
trimmed.SkipOver = TimeSpan.FromSeconds(15);
trimmed.Take = TimeSpan.FromSeconds(10);
var player = new WaveOutEvent();
player.Init(trimmed);
player.Play();
Of course you could equally use WaveFileWriter to write the extract to a WAV file if you wanted to save it for playback later.
Comments
How do you do this if the input is a MemoryStream not a file. I've already reading the file in and have manipulated the contents. What is the solution for this situation.
po poflause `RawSourceWaveStream` and convert it to an `ISampleProvider` with the `ToSampleProvider` extension
Mark HeathI had a hard drive failure and subsequently opted for data recovery services. The hard drive I received back from the data recovery process has a lot of corrupted mp3 files. I've tried to repair them using MP3RepairTool to no avail. Before I give up and delete the files, I want to see if I can find any readable data within the file; even if it's just a few seconds at a random location within the file. I want to know if I'm deleting an audio file of my own creation or a copy of music I've purchased. Is this possible with NAudio or any other API that you are aware of? It sounds like NAudio will do this with a good file but I'm working with corrupt files so I am not sure if it's worth the time. Thanks.
rcirrus98This is great if you're not skipping too far ahead. I have some audio books which can be 6+ hours in duration. If I want to skip to say Chapter 8 (which could be well over an hour+ into the book), it takes over 2+ minutes for the OffsetSampleProvider to reach this point.
cmw ErieYes, a good point. If you're using an AudioFileReader/Mp3FileReader etc, then you can always just set the Position directly to skip to a certain position.
Mark HeathThanks for the tip! I was looking at this property in the AudioFileReader today. It looks like it accepts the byte position within the file. How would I quickly find this based on the time I want to start at?
cmw ErieMark. I found the answer. https://stackoverflow.com/a...
cmw ErieHi Mark, without actually opening a video file would it be possible to extract the audio wave information(hertz and amplitude) with its timestamp of it and stored to a file?
MusicEnthusiast:)