Lyra V2 (1.2.0) is now available. This release increases the quality and flexibility of the model. We recommend all users upgrade if they do not need to use the V1 bitstream.

New Features

• Speed is significantly faster (~5x improvement seen on Android devices).
• The SoundStream-based model produces significantly higher quality speech (when comparing 3kbps V1 to 3.2 kbps V2).
• Selectable bitrate (3200, 6000, 9200 bits per second).
• Codec latency reduced from 100 ms to 20 ms.
• Mac and Windows support (in addition to continuing support for Linux and Android). Note: we have verified that these build, and run correctly, but have numerous compilation and linker warnings (Windows in particular due to MSVC/gcc mismatch). These issues and support for other platforms like iOS can be addressed by modifying the .bazelrc file. We welcome community contributions for this.
• More portable code: The TensorFlow Lite model in the .tflite files can be used in other platforms. The TFLite runtime is optimized for individual platforms, replacing the need to write platform specific assembly.

Breaking Changes

• The V2 bitstream is incompatible with V1.
• Bitrate can now be set dynamically on the encoder using the new set_bitrate() API. Likewise, the bitrate parameter of the decoder was dropped, since it will decode each packet correctly, regardless of bitrate.
• DecodePacketLoss() API was folded into DecodeSamples(), which now switches to Packet Loss Concealment (PLC) when needed.
• lyra_encoder.h API changes
  • Addition of set_bitrate()
  • Encode() returns std::optional instead of absl::optional
• lyra_decoder.h API changes
  • Removal of bitrate as an argument to Create()
  • Removal of DecodePacketLoss()
  • DecodeSamples() returns std::optional instead of absl::optional
  • Removal of bitrate()