Implement idle mode with placeholder content when stream disconnects (#3)

* Initial plan for issue

* Implement placeholder frame generation and idle mode logic

Co-authored-by: v0l <1172179+v0l@users.noreply.github.com>

* Add frame rate throttling for idle mode processing

Co-authored-by: v0l <1172179+v0l@users.noreply.github.com>

* Refactor placeholder generation into separate module and simplify idle mode approach

Co-authored-by: v0l <1172179+v0l@users.noreply.github.com>

* Address PR review feedback: improve parameter naming, fix memory leaks, refactor state management, and fix frame generation approach

Co-authored-by: v0l <1172179+v0l@users.noreply.github.com>

* Store demuxer info in PipelineConfig for placeholder generation

Co-authored-by: v0l <1172179+v0l@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: v0l <1172179+v0l@users.noreply.github.com>

crates/core/src/pipeline/mod.rs

@@ -1,11 +1,13 @@
 use std::fmt::{Display, Formatter};
 
 use crate::egress::EgressConfig;
+use crate::overseer::IngressInfo;
 use crate::variant::VariantStream;
 use serde::{Deserialize, Serialize};
 use uuid::Uuid;
 
 pub mod runner;
+pub mod placeholder;
 
 #[derive(Clone, Debug, Serialize, Deserialize)]
 pub enum EgressType {
@@ -46,6 +48,8 @@ pub struct PipelineConfig {
     pub variants: Vec<VariantStream>,
     /// Output muxers
     pub egress: Vec<EgressType>,
+    /// Source stream information for placeholder generation
+    pub ingress_info: Option<IngressInfo>,
 }
 
 impl Display for PipelineConfig {

crates/core/src/pipeline/placeholder.rs

@@ -0,0 +1,188 @@
+use anyhow::{bail, Result};
+use crate::variant::video::VideoVariant;
+use crate::variant::audio::AudioVariant;
+use crate::overseer::{IngressStream, IngressStreamType};
+use ffmpeg_rs_raw::ffmpeg_sys_the_third::{
+    av_frame_alloc, av_frame_get_buffer, av_frame_free, av_get_sample_fmt, AVFrame, 
+    AVPixelFormat, AVSampleFormat
+};
+use std::ffi::CString;
+
+/// Placeholder frame generator for idle mode when stream disconnects
+pub struct PlaceholderGenerator;
+
+impl PlaceholderGenerator {
+    /// Generate a placeholder video frame based on ingress stream info
+    pub unsafe fn generate_video_frame_from_stream(
+        stream: &IngressStream,
+        stream_time_base: (i32, i32),
+        frame_index: u64
+    ) -> Result<*mut AVFrame> {
+        let frame = av_frame_alloc();
+        if frame.is_null() {
+            bail!("Failed to allocate placeholder video frame");
+        }
+
+        (*frame).format = AVPixelFormat::AV_PIX_FMT_YUV420P as i32;
+        (*frame).width = stream.width as i32;
+        (*frame).height = stream.height as i32;
+        (*frame).time_base.num = stream_time_base.0;
+        (*frame).time_base.den = stream_time_base.1;
+        
+        // Set PTS based on frame rate and total frame index
+        let fps = if stream.fps > 0.0 { stream.fps } else { 30.0 };
+        let time_base_f64 = stream_time_base.0 as f64 / stream_time_base.1 as f64;
+        (*frame).pts = (frame_index as f64 / fps / time_base_f64) as i64;
+
+        if av_frame_get_buffer(frame, 0) < 0 {
+            av_frame_free(&mut frame);
+            bail!("Failed to allocate buffer for placeholder video frame");
+        }
+
+        // Fill with black (Y=16, U=V=128 for limited range YUV420P)
+        let y_size = ((*frame).width * (*frame).height) as usize;
+        let uv_size = y_size / 4;
+        
+        if !(*frame).data[0].is_null() {
+            std::ptr::write_bytes((*frame).data[0], 16, y_size);
+        }
+        if !(*frame).data[1].is_null() {
+            std::ptr::write_bytes((*frame).data[1], 128, uv_size);
+        }
+        if !(*frame).data[2].is_null() {
+            std::ptr::write_bytes((*frame).data[2], 128, uv_size);
+        }
+
+        Ok(frame)
+    }
+
+    /// Generate a placeholder audio frame based on ingress stream info  
+    pub unsafe fn generate_audio_frame_from_stream(
+        stream: &IngressStream,
+        stream_time_base: (i32, i32),
+        frame_index: u64,
+        sample_fmt: &str,
+        channels: u32
+    ) -> Result<*mut AVFrame> {
+        let frame = av_frame_alloc();
+        if frame.is_null() {
+            bail!("Failed to allocate placeholder audio frame");
+        }
+
+        // Use the provided sample format
+        let sample_fmt_cstr = CString::new(sample_fmt)
+            .map_err(|_| anyhow::anyhow!("Invalid sample format string"))?;
+        let sample_fmt_int = av_get_sample_fmt(sample_fmt_cstr.as_ptr());
+        (*frame).format = sample_fmt_int;
+        (*frame).channels = channels as i32;
+        (*frame).sample_rate = stream.sample_rate as i32;
+        (*frame).nb_samples = 1024; // Standard audio frame size
+        (*frame).time_base.num = stream_time_base.0;
+        (*frame).time_base.den = stream_time_base.1;
+        
+        // Set PTS based on sample rate and frame index
+        let samples_per_second = stream.sample_rate as f64;
+        let time_base_f64 = stream_time_base.0 as f64 / stream_time_base.1 as f64;
+        (*frame).pts = ((frame_index * 1024) as f64 / samples_per_second / time_base_f64) as i64;
+
+        if av_frame_get_buffer(frame, 0) < 0 {
+            av_frame_free(&mut frame);
+            bail!("Failed to allocate buffer for placeholder audio frame");
+        }
+
+        // Fill with silence (zeros)
+        for i in 0..8 {
+            if !(*frame).data[i].is_null() && (*frame).linesize[i] > 0 {
+                std::ptr::write_bytes((*frame).data[i], 0, (*frame).linesize[i] as usize);
+            }
+        }
+
+        Ok(frame)
+    }
+
+    /// Generate a placeholder black video frame
+    pub unsafe fn generate_video_frame(
+        variant: &VideoVariant, 
+        stream_time_base: (i32, i32),
+        frame_index: u64
+    ) -> Result<*mut AVFrame> {
+        let frame = av_frame_alloc();
+        if frame.is_null() {
+            bail!("Failed to allocate placeholder video frame");
+        }
+
+        (*frame).format = AVPixelFormat::AV_PIX_FMT_YUV420P as i32;
+        (*frame).width = variant.width as i32;
+        (*frame).height = variant.height as i32;
+        (*frame).time_base.num = stream_time_base.0;
+        (*frame).time_base.den = stream_time_base.1;
+        
+        // Set PTS based on frame rate and total frame index
+        let fps = if variant.fps > 0.0 { variant.fps } else { 30.0 };
+        let time_base_f64 = stream_time_base.0 as f64 / stream_time_base.1 as f64;
+        (*frame).pts = (frame_index as f64 / fps / time_base_f64) as i64;
+
+        if av_frame_get_buffer(frame, 0) < 0 {
+            av_frame_free(&mut frame);
+            bail!("Failed to allocate buffer for placeholder video frame");
+        }
+
+        // Fill with black (Y=16, U=V=128 for limited range YUV420P)
+        let y_size = ((*frame).width * (*frame).height) as usize;
+        let uv_size = y_size / 4;
+        
+        if !(*frame).data[0].is_null() {
+            std::ptr::write_bytes((*frame).data[0], 16, y_size);
+        }
+        if !(*frame).data[1].is_null() {
+            std::ptr::write_bytes((*frame).data[1], 128, uv_size);
+        }
+        if !(*frame).data[2].is_null() {
+            std::ptr::write_bytes((*frame).data[2], 128, uv_size);
+        }
+
+        Ok(frame)
+    }
+
+    /// Generate a placeholder silent audio frame
+    pub unsafe fn generate_audio_frame(
+        variant: &AudioVariant, 
+        stream_time_base: (i32, i32),
+        frame_index: u64
+    ) -> Result<*mut AVFrame> {
+        let frame = av_frame_alloc();
+        if frame.is_null() {
+            bail!("Failed to allocate placeholder audio frame");
+        }
+
+        // Use the sample format from the variant configuration
+        let sample_fmt_cstr = CString::new(variant.sample_fmt.as_str())
+            .map_err(|_| anyhow::anyhow!("Invalid sample format string"))?;
+        let sample_fmt_int = av_get_sample_fmt(sample_fmt_cstr.as_ptr());
+        (*frame).format = sample_fmt_int;
+        (*frame).channels = variant.channels as i32;
+        (*frame).sample_rate = variant.sample_rate as i32;
+        (*frame).nb_samples = 1024; // Standard audio frame size
+        (*frame).time_base.num = stream_time_base.0;
+        (*frame).time_base.den = stream_time_base.1;
+        
+        // Set PTS based on sample rate and frame index
+        let samples_per_second = variant.sample_rate as f64;
+        let time_base_f64 = stream_time_base.0 as f64 / stream_time_base.1 as f64;
+        (*frame).pts = ((frame_index * 1024) as f64 / samples_per_second / time_base_f64) as i64;
+
+        if av_frame_get_buffer(frame, 0) < 0 {
+            av_frame_free(&mut frame);
+            bail!("Failed to allocate buffer for placeholder audio frame");
+        }
+
+        // Fill with silence (zeros)
+        for i in 0..8 {
+            if !(*frame).data[i].is_null() && (*frame).linesize[i] > 0 {
+                std::ptr::write_bytes((*frame).data[i], 0, (*frame).linesize[i] as usize);
+            }
+        }
+
+        Ok(frame)
+    }
+}

crates/core/src/pipeline/runner.rs

@@ -5,7 +5,7 @@ use std::ops::Sub;
 use std::path::PathBuf;
 use std::ptr;
 use std::sync::Arc;
-use std::time::Instant;
+use std::time::{Duration, Instant};
 
 use crate::egress::hls::HlsEgress;
 use crate::egress::recorder::RecorderEgress;
@@ -15,6 +15,7 @@ use crate::mux::SegmentType;
 use crate::overseer::{IngressInfo, IngressStream, IngressStreamType, Overseer};
 use crate::pipeline::{EgressType, PipelineConfig};
 use crate::variant::{StreamMapping, VariantStream};
+use crate::pipeline::placeholder::PlaceholderGenerator;
 use anyhow::{bail, Result};
 use ffmpeg_rs_raw::ffmpeg_sys_the_third::AVCodecID::AV_CODEC_ID_WEBP;
 use ffmpeg_rs_raw::ffmpeg_sys_the_third::AVPictureType::AV_PICTURE_TYPE_NONE;
@@ -30,6 +31,19 @@ use log::{error, info, warn};
 use tokio::runtime::Handle;
 use uuid::Uuid;
 
+/// Runner state for handling normal vs idle modes
+#[derive(Debug, Clone)]
+pub enum RunnerState {
+    /// Normal operation - processing live stream
+    Normal,
+    /// Idle mode - generating placeholder content after disconnection
+    Idle {
+        start_time: Instant,
+        variant_index: usize,
+        last_frame_time: Option<Instant>,
+    },
+}
+
 /// Pipeline runner is the main entry process for stream transcoding
 ///
 /// Each client connection spawns a new [PipelineRunner] and it should be run in its own thread
@@ -80,6 +94,9 @@ pub struct PipelineRunner {
 
     /// Thumbnail generation interval (0 = disabled)
     thumb_interval: u64,
+
+    /// Current runner state (normal or idle)
+    state: RunnerState,
 }
 
 impl PipelineRunner {
@@ -108,9 +125,148 @@ impl PipelineRunner {
             fps_last_frame_ctr: 0,
             info: None,
             thumb_interval: 1800, // Disable thumbnails by default for performance
+            state: RunnerState::Normal,
         })
     }
 
+    /// Process a single idle frame - generates one source frame and processes it through all variants
+    unsafe fn process_single_idle_frame(&mut self, config: &PipelineConfig) -> Result<()> {
+        use std::time::{Duration, Instant};
+        
+        if config.variants.is_empty() {
+            return Ok(());
+        }
+
+        // Extract timing info from current state
+        let (mut last_frame_time, variant_index) = match &mut self.state {
+            RunnerState::Idle { last_frame_time, variant_index, .. } => (last_frame_time, variant_index),
+            _ => return Ok(()), // Only process in idle state
+        };
+
+        // Time-based frame rate calculation
+        let now = Instant::now();
+        if let Some(last_time) = *last_frame_time {
+            // Calculate target frame interval (assume 30fps for now)
+            let target_interval = Duration::from_millis(33); // ~30fps
+            let elapsed = now.duration_since(last_time);
+            
+            if elapsed < target_interval {
+                // Not time for next frame yet
+                std::thread::sleep(target_interval - elapsed);
+            }
+        }
+        *last_frame_time = Some(Instant::now());
+
+        // Get source video stream info from stored ingress info
+        let video_stream = config.ingress_info.as_ref()
+            .and_then(|info| info.streams.iter().find(|s| matches!(s.stream_type, crate::overseer::IngressStreamType::Video)));
+
+        let mut egress_results = vec![];
+
+        // Generate one source frame and process it through all relevant variants
+        if let Some(stream) = video_stream {
+            // Generate a single source placeholder video frame based on original stream properties
+            let fps = if stream.fps > 0.0 { stream.fps } else { 30.0 };
+            let time_base = (1, fps as i32);
+            let mut source_frame = PlaceholderGenerator::generate_video_frame_from_stream(stream, time_base, self.frame_ctr)?;
+            
+            // Set the frame time_base
+            (*source_frame).time_base.num = time_base.0;
+            (*source_frame).time_base.den = time_base.1;
+            
+            // Increment frame counter for all video processing
+            self.frame_ctr += 1;
+            
+            // Process this single frame through all video variants (like normal pipeline)
+            for variant in &config.variants {
+                if let VariantStream::Video(v) = variant {
+                    // Scale/encode the source frame for this variant
+                    if let Some(enc) = self.encoders.get_mut(&v.id()) {
+                        // Use scaler if needed for different resolutions
+                        let frame_to_encode = if v.width as i32 == (*source_frame).width && 
+                                                v.height as i32 == (*source_frame).height {
+                            // Same resolution, use source frame directly
+                            source_frame
+                        } else {
+                            // Different resolution, need to scale
+                            if let Some(scaler) = self.scalers.get_mut(&v.id()) {
+                                scaler.process_frame(source_frame, v.width, v.height, AV_PIX_FMT_YUV420P)?
+                            } else {
+                                source_frame // Fallback to source frame
+                            }
+                        };
+
+                        let packets = enc.encode_frame(frame_to_encode)?;
+                        for mut pkt in packets {
+                            for eg in self.egress.iter_mut() {
+                                let er = eg.process_pkt(pkt, &v.id())?;
+                                egress_results.push(er);
+                            }
+                            av_packet_free(&mut pkt);
+                        }
+                    }
+                }
+            }
+            
+            av_frame_free(&mut source_frame);
+        }
+
+        // Generate and process audio frames separately (audio doesn't share like video)
+        let audio_stream = config.ingress_info.as_ref()
+            .and_then(|info| info.streams.iter().find(|s| matches!(s.stream_type, crate::overseer::IngressStreamType::Audio)));
+            
+        for variant in &config.variants {
+            if let VariantStream::Audio(a) = variant {
+                let time_base = (1, a.sample_rate as i32);
+                let mut frame = if let Some(stream) = audio_stream {
+                    // Use original stream properties for placeholder generation
+                    PlaceholderGenerator::generate_audio_frame_from_stream(stream, time_base, self.frame_ctr, &a.sample_fmt, a.channels)?
+                } else {
+                    // Fallback to variant properties if no stream info available
+                    PlaceholderGenerator::generate_audio_frame(a, time_base, self.frame_ctr)?
+                };
+                
+                // Set the frame time_base
+                (*frame).time_base.num = time_base.0;
+                (*frame).time_base.den = time_base.1;
+                
+                // Process through the encoding pipeline
+                if let Some(enc) = self.encoders.get_mut(&a.id()) {
+                    let packets = enc.encode_frame(frame)?;
+                    for mut pkt in packets {
+                        for eg in self.egress.iter_mut() {
+                            let er = eg.process_pkt(pkt, &a.id())?;
+                            egress_results.push(er);
+                        }
+                        av_packet_free(&mut pkt);
+                    }
+                }
+                
+                av_frame_free(&mut frame);
+            }
+        }
+        
+        // Handle egress results (same as normal processing)
+        if !egress_results.is_empty() {
+            self.handle.block_on(async {
+                for er in egress_results {
+                    if let EgressResult::Segments { created, deleted } = er {
+                        if let Err(e) = self
+                            .overseer
+                            .on_segments(&config.id, &created, &deleted)
+                            .await
+                        {
+                            bail!("Failed to process segment {}", e.to_string());
+                        }
+                    }
+                }
+                Ok(())
+            })?;
+        }
+        
+        Ok(())
+    }
+
     /// EOF, cleanup
     pub unsafe fn flush(&mut self) -> Result<()> {
         for (var, enc) in &mut self.encoders {
@@ -147,22 +303,67 @@ impl PipelineRunner {
         };
 
         // run transcoder pipeline
-        let (mut pkt, _stream) = self.demuxer.get_packet()?;
-        if pkt.is_null() {
-            return Ok(false);
+        let (mut pkt, stream_info) = self.demuxer.get_packet()?;
+        
+        // Handle state transitions based on packet availability
+        match (&self.state, pkt.is_null()) {
+            (RunnerState::Normal, true) => {
+                // First time entering idle mode
+                info!("Stream input disconnected, entering idle mode with placeholder content");
+                self.state = RunnerState::Idle {
+                    start_time: Instant::now(),
+                    variant_index: 0,
+                    last_frame_time: None,
+                };
+            }
+            (RunnerState::Idle { start_time, .. }, true) => {
+                // Check if we've been idle for more than 1 minute
+                if start_time.elapsed() > Duration::from_secs(60) {
+                    info!("Idle timeout reached (60 seconds), ending stream");
+                    return Ok(false);
+                }
+            }
+            (RunnerState::Idle { .. }, false) => {
+                // Stream reconnected
+                info!("Stream reconnected, leaving idle mode");
+                self.state = RunnerState::Normal;
+            }
+            (RunnerState::Normal, false) => {
+                // Normal operation continues
+            }
         }
         
-        // TODO: For copy streams, skip decoder
-        let frames = match self.decoder.decode_pkt(pkt) {
-            Ok(f) => f,
-            Err(e) => {
-                warn!("Error decoding frames, {e}");
-                return Ok(true);
-            }
-        };
+        // Process based on current state
+        match &self.state {
+            RunnerState::Idle { .. } => {
+                // Process a single idle frame (rotating through variants)
+                self.process_single_idle_frame(config)?;
                 
-        let mut egress_results = vec![];
-        for (frame, stream) in frames {
+                // Free the null packet if needed
+                if !pkt.is_null() {
+                    av_packet_free(&mut pkt);
+                }
+                
+                return Ok(true); // Continue processing
+            }
+            RunnerState::Normal => {
+                // Normal packet processing
+                if pkt.is_null() {
+                    // This shouldn't happen in Normal state but handle gracefully
+                    return Ok(true);
+                }
+                
+                // TODO: For copy streams, skip decoder
+                let frames = match self.decoder.decode_pkt(pkt) {
+                    Ok(f) => f,
+                    Err(e) => {
+                        warn!("Error decoding frames, {e}");
+                        return Ok(true);
+                    }
+                };
+
+                let mut egress_results = vec![];
+                for (frame, stream) in frames {
             // Copy frame from GPU if using hwaccel decoding
             let mut frame = get_frame_from_hw(frame)?;
             (*frame).time_base = (*stream).time_base;
@@ -309,6 +510,8 @@ impl PipelineRunner {
             info!("Average fps: {:.2}", n_frames as f32 / elapsed);
             self.fps_counter_start = Instant::now();
             self.fps_last_frame_ctr = self.frame_ctr;
+        }
+            } // Close the RunnerState::Normal match arm
         }
         Ok(true)
     }
@@ -344,9 +547,13 @@ impl PipelineRunner {
                 .collect(),
         };
 
-        let cfg = self
+        let mut cfg = self
             .handle
             .block_on(async { self.overseer.start_stream(&self.connection, &i_info).await })?;
+        
+        // Store ingress info in config for placeholder generation
+        cfg.ingress_info = Some(i_info.clone());
+        
         self.config = Some(cfg);
         self.info = Some(i_info);