epnw / opus_dart Goto Github PK

Hi thanks for this wonderful library! I wonder whether we can use this to record opus audios and play opus audios?

Since some methods in the ffi package (not the dart:ffi namespace) are not longer supported with newer dart versions, opus dart does no longer work. I'm currently working on a fix.

This should be multiplied by 4 (to account for float output):

The opus encoders an decoders take lists of ints or floats in / put lists of ints or floats out. The Int16List and Float32List dart classes are used therefor. Datatypes with a byte size greater than one are subject to an endianess. Dart doesn't let uns inflence what the endianess in such a list is, and just assumes big endian when e.g. calling ByteBuffer.asFloat32List. But most pcm data are recorded and played with little endian, and especially opus only works with little endian data (as far as I know).

All this means that:

• if you where about to actually access an value in an Int16List put out by an opus decoder in dart and want to actually work with it (like filtering, ...), it is most likely in the wrong byte order, and thus you work with an int that "has the wrong value"
• if you construct an Int16List on your own in dart using actuall numerical values for its entries and pass it to an encoder, you would not get any meaningfull output from that encoder, since opus needs the byte order to be little endian

If you just use the data from the decoder to play audio there should be no problem, since the thing playing the data most likely assumes little endian anyway, and if you just use the encoder to encode recorded data, there also should be no problem, since these data are moste likely recorded using little endian.

In the next update of opus_dart we should document the endian behaviour in more detail.

The package opus_flutter appears to have been removed from pub.dev. Do you know where it went?

Hi,

I'm trying to encode audio data using the SimpleOpusEncoder.
But I get the error:

Future<void> main() async {
  initOpus(await opus_flutter.load());
  runApp(const MyApp());
}

 SimpleOpusEncoder encoder = SimpleOpusEncoder(sampleRate: 44100, channels: 1, application: Application.voip);


The following OpusException was thrown building Builder:
OpusException -1: invalid argument

libopus 1.3.1

Any ideas why this happens?

Thanks

In the next release, instead of doing

Any plans to support web? Here is a good javascript library that interfaces with the same C library via web assembly.

https://github.com/AnthumChris/opus-stream-decoder