BufferedOpusDecoder class

An implementation of OpusDecoder that uses preallocated buffers. Don't forget to call destroy once you are done with it.

The idea behind this implementation is to reduce the amount of memory allocation calls. Instead of allocating new buffers everytime something is decoded, the buffers are allocated at initalization. Then, an opus packet is directly written into the inputBuffer, the inputBufferIndex is updated, based on how many bytes where written, and one of the deocde methods is called. The decoded pcm samples can then be accessed using the outputBuffer getter (or one of the outputBufferAsInt16List or outputBufferAsFloat32List convenience getters).

BufferedOpusDecoder decoder;

void example() {
  // Get an opus packet
  Uint8List packet = receivePacket();
  // Set the bytes to the input buffer
  decoder.inputBuffer.setAll(0, packet);
  // Update the inputBufferIndex with amount of bytes written
  decoder.inputBufferIndex = packet.length;
  // decode
  decoder.decode();
  // Interpret the output as s16le
  Int16List pcm = decoder.outputBufferAsInt16List;
  doSomething(pcm);
}
Inheritance

Constructors

BufferedOpusDecoder({required int sampleRate, required int channels, int? maxInputBufferSizeBytes, int? maxOutputBufferSizeBytes})
Creates an new BufferedOpusDecoder based on the sampleRate and channels. The native allocated buffer size is determined by maxInputBufferSizeBytes and maxOutputBufferSizeBytes.
factory

Properties

channels → int
Number of channels, must be 1 for mono or 2 for stereo.
final
destroyed → bool
Wheter this decoder was already destroyed by calling destroy. If so, calling any method will result in an OpusDestroyedError.
no setteroverride
hashCode → int
The hash code for this object.
no setterinherited
inputBuffer → Uint8List
Returns the native input buffer backed by native memory.
no setter
inputBufferIndex ↔ int
Indicates, how many bytes of data are currently stored in the inputBuffer.
getter/setter pair
lastPacketDurationMs → int?
The duration of the last decoded packet in ms or null if there was no packet yet.
no setteroverride
maxInputBufferSizeBytes → int
The size of the allocated the input buffer in bytes. Should be choosen big enough to hold a maximal opus packet with size of maxDataBytes bytes.
final
maxOutputBufferSizeBytes → int
The size of the allocated the output buffer. If this value is choosen to small, this decoder will not be capable of decoding some packets.
final
outputBuffer → Uint8List
The portion of the allocated output buffer that is currently filled with data. The data are pcm samples, either encoded as s16le or floats, depending on what method was used to decode the input packet.
no setter
outputBufferAsFloat32List → Float32List
Convenience method to get the current output buffer as floats.
no setter
outputBufferAsInt16List → Int16List
Convenience method to get the current output buffer as s16le.
no setter
runtimeType → Type
A representation of the runtime type of the object.
no setterinherited
sampleRate → int
The sample rate in Hz for this decoder. Opus supports sample rates from 8kHz to 48kHz so this value must be between 8000 and 48000.
final

Methods

decode({bool fec = false, int? loss}) → Int16List
Interpretes inputBufferIndex bytes from the inputBuffer as a whole opus packet and decodes them to s16le samples, stored in the outputBuffer. Set inputBufferIndex to 0 to indicate packet loss.
override
decodeFloat({bool autoSoftClip = false, bool fec = false, int? loss}) → Float32List
Interpretes inputBufferIndex bytes from the inputBuffer as a whole opus packet and decodes them to float samples, stored in the outputBuffer. Set inputBufferIndex to 0 to indicate packet loss.
override
destroy() → void
Destroys this decoder by releasing all native resources. After this, it is no longer possible to decode using this decoder, so any further method call will throw an OpusDestroyedError.
override
noSuchMethod(Invocation invocation) → dynamic
Invoked when a nonexistent method or property is accessed.
inherited
pcmSoftClipOutputBuffer() → Float32List
Performs soft clipping on the outputBuffer.
toString() → String
A string representation of this object.
inherited

Operators

operator ==(Object other) → bool
The equality operator.
inherited