private bool ProcessPacket(ReadOnlySpan <byte> data, ref Memory <byte> opus, ref Memory <byte> pcm, IList <ReadOnlyMemory <byte> > pcmPackets, out AudioSender voiceSender, out AudioFormat outputFormat) { voiceSender = null; outputFormat = default; if (!Rtp.IsRtpHeader(data)) { return(false); } Rtp.DecodeHeader(data, out var sequence, out var timestamp, out var ssrc, out var hasExtension); var vtx = TransmittingSSRCs[ssrc]; voiceSender = vtx; if (sequence <= vtx.LastSequence) // out-of-order packet; discard { return(false); } var gap = vtx.LastSequence != 0 ? sequence - 1 - vtx.LastSequence : 0; if (gap >= 5) { Discord.DebugLogger.LogMessage(LogLevel.Warning, "VNext RX", "5 or more voice packets were dropped when receiving", DateTime.Now); } Span <byte> nonce = new byte[Sodium.NonceSize]; Sodium.GetNonce(data, nonce, SelectedEncryptionMode); Rtp.GetDataFromPacket(data, out var encryptedOpus, SelectedEncryptionMode); var opusSize = Sodium.CalculateSourceSize(encryptedOpus); opus = opus.Slice(0, opusSize); var opusSpan = opus.Span; try { Sodium.Decrypt(encryptedOpus, opusSpan, nonce); // Strip extensions, if any if (hasExtension) { // RFC 5285, 4.2 One-Byte header // http://www.rfcreader.com/#rfc5285_line186 if (opusSpan[0] == 0xBE && opusSpan[1] == 0xDE) { var headerLen = opusSpan[2] << 8 | opusSpan[3]; var i = 4; for (; i < headerLen + 4; i++) { var @byte = opusSpan[i]; // ID is currently unused since we skip it anyway //var id = (byte)(@byte >> 4); var length = (byte)(@byte & 0x0F) + 1; i += length; } // Strip extension padding too while (opusSpan[i] == 0) { i++; } opusSpan = opusSpan.Slice(i); } // TODO: consider implementing RFC 5285, 4.3. Two-Byte Header } if (gap == 1) { var lastSampleCount = Opus.GetLastPacketSampleCount(vtx.Decoder); var fecpcm = new byte[AudioFormat.SampleCountToSampleSize(lastSampleCount)]; var fecpcmMem = fecpcm.AsSpan(); Opus.Decode(vtx.Decoder, opusSpan, ref fecpcmMem, true, out _); pcmPackets.Add(fecpcm.AsMemory(0, fecpcmMem.Length)); } else if (gap > 1) { var lastSampleCount = Opus.GetLastPacketSampleCount(vtx.Decoder); for (var i = 0; i < gap; i++) { var fecpcm = new byte[AudioFormat.SampleCountToSampleSize(lastSampleCount)]; var fecpcmMem = fecpcm.AsSpan(); Opus.ProcessPacketLoss(vtx.Decoder, lastSampleCount, ref fecpcmMem); pcmPackets.Add(fecpcm.AsMemory(0, fecpcmMem.Length)); } } var pcmSpan = pcm.Span; Opus.Decode(vtx.Decoder, opusSpan, ref pcmSpan, false, out outputFormat); pcm = pcm.Slice(0, pcmSpan.Length); } finally { vtx.LastSequence = sequence; } return(true); }