mirror of https://github.com/jetkvm/kvm.git
Cleanup: remove silence detection
This commit is contained in:
Alex P
parent
35b5dbd034
commit
70ef7193fd
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@ -1,9 +1,18 @@
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/*
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* JetKVM Audio Processing Module
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*
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* This module handles bidirectional audio processing for JetKVM:
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* - Audio INPUT: Client microphone → Device speakers (decode Opus → ALSA playback)
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* - Audio OUTPUT: TC358743 HDMI audio → Client speakers (ALSA capture → encode Opus)
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* Bidirectional audio processing optimized for ARM NEON SIMD:
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* - OUTPUT PATH: TC358743 HDMI audio → Client speakers
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* Pipeline: ALSA hw:0,0 capture → 2.5x gain → Opus encode (96kbps, FEC enabled)
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*
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* - INPUT PATH: Client microphone → Device speakers
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* Pipeline: Opus decode (with FEC) → ALSA hw:1,0 playback
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*
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* Key features:
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* - ARM NEON SIMD optimization for all audio operations
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* - Opus in-band FEC for packet loss resilience
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* - Ultra-low CPU usage (~0.5% on RV1106)
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* - S16_LE @ 48kHz stereo, 20ms frames (960 samples)
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*/
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#include <alsa/asoundlib.h>
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@ -46,14 +55,14 @@ static int channels = 2;
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static int frame_size = 960; // 20ms frames at 48kHz
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// Opus encoder settings (optimized for minimal CPU ~0.5% on RV1106)
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static int opus_bitrate = 96000; // 96 kbps
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static int opus_complexity = 1; // Complexity 1 (minimal CPU)
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static int opus_bitrate = 96000; // 96 kbps - good quality/bandwidth balance
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static int opus_complexity = 1; // Complexity 1 - minimal CPU usage
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static int opus_vbr = 1; // Variable bitrate enabled
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static int opus_vbr_constraint = 1; // Constrained VBR for predictable bandwidth
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static int opus_signal_type = -1000; // OPUS_AUTO (-1000)
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static int opus_bandwidth = 1103; // OPUS_BANDWIDTH_WIDEBAND (1103)
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static int opus_dtx = 0; // DTX disabled
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static int opus_lsb_depth = 16; // 16-bit depth matches S16_LE
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static int opus_vbr_constraint = 1; // Constrained VBR - predictable bandwidth
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static int opus_signal_type = -1000; // OPUS_AUTO - automatic signal type detection
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static int opus_bandwidth = 1103; // OPUS_BANDWIDTH_WIDEBAND (50-8000 Hz)
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static int opus_dtx = 0; // DTX disabled - no discontinuous transmission
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static int opus_lsb_depth = 16; // 16-bit depth - matches S16_LE format
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// Network configuration
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static int max_packet_size = 1500;
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@ -63,7 +72,7 @@ static int sleep_microseconds = 1000;
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static int max_attempts_global = 5;
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static int max_backoff_us_global = 500000;
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// Buffer optimization (1 = use 2-period ultra-low latency, 0 = use 4-period balanced)
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// ALSA buffer configuration (not currently used - kept for future optimization)
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static const int optimized_buffer_size = 1;
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@ -443,7 +452,8 @@ static volatile int playback_initializing = 0;
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static volatile int playback_initialized = 0;
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/**
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* Update Opus encoder settings at runtime
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* Update Opus encoder settings at runtime (does NOT modify FEC settings)
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* Note: FEC configuration remains unchanged - set at initialization
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* @return 0 on success, -1 if not initialized, >0 if some settings failed
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*/
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int update_opus_encoder_params(int bitrate, int complexity, int vbr, int vbr_constraint,
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@ -452,6 +462,7 @@ int update_opus_encoder_params(int bitrate, int complexity, int vbr, int vbr_con
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return -1;
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}
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// Update global configuration variables
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opus_bitrate = bitrate;
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opus_complexity = complexity;
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opus_vbr = vbr;
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@ -460,6 +471,7 @@ int update_opus_encoder_params(int bitrate, int complexity, int vbr, int vbr_con
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opus_bandwidth = bandwidth;
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opus_dtx = dtx;
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// Apply settings to encoder (FEC settings not modified)
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int result = 0;
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result |= opus_encoder_ctl(encoder, OPUS_SET_BITRATE(opus_bitrate));
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result |= opus_encoder_ctl(encoder, OPUS_SET_COMPLEXITY(opus_complexity));
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@ -630,6 +642,7 @@ int jetkvm_audio_capture_init() {
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return -3;
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}
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// Configure encoder with optimized settings
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opus_encoder_ctl(encoder, OPUS_SET_BITRATE(opus_bitrate));
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opus_encoder_ctl(encoder, OPUS_SET_COMPLEXITY(opus_complexity));
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opus_encoder_ctl(encoder, OPUS_SET_VBR(opus_vbr));
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@ -639,9 +652,10 @@ int jetkvm_audio_capture_init() {
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opus_encoder_ctl(encoder, OPUS_SET_DTX(opus_dtx));
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opus_encoder_ctl(encoder, OPUS_SET_LSB_DEPTH(opus_lsb_depth));
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// Enable in-band FEC for packet loss resilience (adds ~2-5% bitrate)
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// Enable in-band FEC (Forward Error Correction) for network resilience
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// Embeds redundant data in packets to recover from packet loss (adds ~2-5% bitrate overhead)
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opus_encoder_ctl(encoder, OPUS_SET_INBAND_FEC(1));
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opus_encoder_ctl(encoder, OPUS_SET_PACKET_LOSS_PERC(10));
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opus_encoder_ctl(encoder, OPUS_SET_PACKET_LOSS_PERC(10)); // Optimize for 10% expected loss
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capture_initialized = 1;
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capture_initializing = 0;
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@ -650,14 +664,13 @@ int jetkvm_audio_capture_init() {
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/**
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* Read HDMI audio, encode to Opus (OUTPUT path hot function)
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* Processing pipeline: ALSA capture → silence detection → discontinuity detection → 2.5x gain → Opus encode
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* Processing pipeline: ALSA capture → 2.5x gain → Opus encode
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* @param opus_buf Output buffer for encoded Opus packet
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* @return >0 = Opus packet size in bytes, 0 = silence/no data, -1 = error
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* @return >0 = Opus packet size in bytes, -1 = error
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*/
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__attribute__((hot)) int jetkvm_audio_read_encode(void * __restrict__ opus_buf) {
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// Static buffers persist across calls for better cache locality
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static short SIMD_ALIGN pcm_buffer[1920]; // 960 frames × 2 channels
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static short prev_max_sample = 0; // Previous frame peak for discontinuity detection
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// Local variables
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unsigned char * __restrict__ out = (unsigned char*)opus_buf;
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@ -665,8 +678,6 @@ __attribute__((hot)) int jetkvm_audio_read_encode(void * __restrict__ opus_buf)
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int err = 0;
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int recovery_attempts = 0;
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const int max_recovery_attempts = 3;
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int total_samples;
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short max_sample;
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int nb_bytes;
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// Prefetch output buffer for write
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@ -745,31 +756,6 @@ retry_read:
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simd_clear_samples_s16(&pcm_buffer[pcm_rc * channels], remaining_samples);
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}
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// Silence detection: skip frames below ~0.15% of maximum volume
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total_samples = frame_size * channels;
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max_sample = simd_find_max_abs_s16(pcm_buffer, total_samples);
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if (max_sample < 50) {
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prev_max_sample = 0; // Reset discontinuity tracker on silence
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if (trace_logging_enabled) {
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printf("[AUDIO_OUTPUT] jetkvm_audio_read_encode: Silence detected (max=%d), skipping frame\n", max_sample);
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}
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return 0;
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}
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// Discontinuity detection: reset encoder on abrupt level changes (video seeks)
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// Prevents crackling when audio stream jumps due to video seeking
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if (prev_max_sample > 0) {
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int level_ratio = (max_sample > prev_max_sample * 5) || (prev_max_sample > max_sample * 5);
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if (level_ratio) {
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if (trace_logging_enabled) {
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printf("[AUDIO_OUTPUT] Discontinuity detected (%d→%d), resetting encoder\n", prev_max_sample, max_sample);
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}
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opus_encoder_ctl(encoder, OPUS_RESET_STATE);
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}
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}
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prev_max_sample = max_sample;
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// Apply 2.5x gain boost to prevent quantization noise at low volumes
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// HDMI audio typically transmitted at -6 to -12dB; boost prevents Opus noise floor artifacts
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simd_scale_volume_s16(pcm_buffer, frame_size * channels, 2.5f);
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