---
description: "Deep reference: VIOS media pipeline architecture -- GStreamer, WebRTC, RTSP, overlays, codecs"
globs: "src/framework/media/**,src/framework/live555/**,src/framework/webrtc_streamer/**,src/framework/stream_monitor/**"
alwaysApply: false
---

# SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
# SPDX-License-Identifier: Apache-2.0
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

# Core Classes

- **CommonVideoSource** (media/video_source/core/CommonVideoSource.h) -- main controller, delegates to PipelineManager
- **PipelineManager** (core/PipelineManager.h) -- owns pipeline lifecycle, selects builder from PipelineConfiguration
- **PipelineConfiguration** (core/PipelineConfiguration.h) -- URI, peer ID, quality, compositor, overlay options
- **DecoderPool** (decoders/decoderpool.h) -- singleton pool of GstNvVideoDecoder keyed by URL (shared for live, dedicated for record/capture)
- **VideoSenderPool** (senders/videosenderpool.h) -- singleton pool of VideoWebRTCSender for pass-through

# Producer-Consumer Model

- **IMediaDataProducer**: StreamMonitor (RTSP/live555), WebrtcStreamProducer, CloudStreamProducer, ClipReaderProducer
- **IMediaDataConsumer** (media_consumer.h): NvEncoderVideoConsumer, NvLLOverlay, NvCompositor, WebrtcSinkConsumer, ImageEnc, TranscodeWriterConsumer, RemuxWriterConsumer

# Pipeline Selection (PipelineBuilder pattern)

```
compositor.enabled -> CompositePipelineBuilder (multi-stream tiles)
else -> SingleStreamPipelineBuilder:
  isPassThrough()    -> PassThroughPipeline (no re-encode)
  isNativeStream()   -> NativeStreamPipeline (/dev/video*)
  isGodsEyeView()    -> GodsEyeViewPipeline (file playback)
  ipc_path enabled   -> IPCPipeline (Jetson bbox)
  else               -> StandardPipeline (decode->overlay->encode->WebRTC)
```

# Pipeline Chains by Use Case

| Use Case | Chain |
|----------|-------|
| Live view | RTSP/StreamMonitor -> GstNvVideoDecoder -> NvLLTransform -> NvLLOverlay -> NvEncoderVideoConsumer -> WebrtcSinkConsumer |
| Pass-through | RTSP -> GstNvVideoDecoder -> VideoWebRTCSender (direct H.264/H.265 to WebRTC) |
| Recording (transcode) | appsrc -> transcodebin (decode->overlay->encode) -> mux -> filesink |
| Recording (remux) | appsrc -> parser -> mux -> filesink (no decode/encode) |
| Composite | Decoder[1..N] -> Overlay[1..N] -> NvCompositor (GridLayout) -> Transform -> Encoder -> WebRTC |
| Image capture | Decoder -> Transform -> Overlay -> ImageEnc -> JPEG buffer |

# Overlay System

- **NvLLOverlay** (overlays/ll_overlay.h) -- IMediaDataConsumer, uses draw thread with queue + condvar
- **NvLLOverlayInternal** (overlays/overlay_internal.h) -- OSD via NvOsdLibs (CUDA), draws bbox/tripwire/ROI/pose/halo
- Metadata from **LiveMetadataStore** (Redis) or **ElasticMetadataStore** (Elasticsearch)
- Flow: Decoder -> `onFrame(RawFrameParams)` -> queue -> `doDrawTask` -> `NvLLOverlayInternal::doDraw()` -> consumer

# WebRTC Flow

- **NvGstVideoSource** (webrtc_streamer/nvgstvideosource.h) -- wraps CommonVideoSource + rtc::VideoBroadcaster
- **WebrtcSinkConsumer** -- receives YUV (I420Buffer -> webrtc::VideoFrame -> broadcaster) or bitstream (-> VideoWebRTCSender)
- **PeerConnectionManager** -- creates PeerConnection instances, handles SDP/ICE, uses CapturerFactory

# RTSP Client (live555)

- **RTSPConnection** (live555helper/rtspconnectionclient.h) -- wraps live555 RTSPClient, supports UDP/TCP/HTTP
- **SessionSink** (live555helper/SessionSink.h) -- `afterGettingFrame()` -> `SessionCallback::onData()` with RTP payload
- **StreamMonitor** -- IMediaDataProducer + SessionCallback, `QosRtspClient` manages RTSP session
- `registerDataCallback(url, consumer)` adds decoder as consumer; frames delivered via `onFrame(FrameParams&)` -> `pushBufferToDecoder()` into appsrc

# Buffer Management

- **RawFrameParams** (media_consumer.h:79-151) -- holds `GstBuffer*`, `GstMapInfo`, fd, `NvBufSurface`; `m_owns_gstBuffer` controls ownership
- Supports NVMM (`memory:NVMM`) for zero-copy GPU buffers
- **NvSurfacePool** -- reusable surface pool for encoder/overlay

# HW Acceleration

- **NvDecodeBin** (gstnvdecodebin.h) -- builds nvh264dec/nvh265dec when `NvHwDetection::m_useNvV4l2Dec`; software fallback otherwise
- **NvEncoderVideoConsumer** -- uses nvv4l2h264enc/nvv4l2h265enc when `NvHwDetection::m_useNvV4l2Enc`
- Guards: `#ifdef USE_NV_ENC` / `#ifdef USE_NV_DEC` (aarch64)

# Error Recovery

- **GstNvVideoDecoder**: bus handler, non-fatal errors retry `m_resetAttempts` (3) then `controlStream("reset_pipeline")`. Fatal (GPU gone): `exit(EXIT_GPU_NOT_FOUND)`
- **GstMux**: `pipelineReset()` on muxer error, recreate on next IDR
- **ClipReaderProducer**: `retryPipeline()` on empty stream, `MAX_EMPTY_STREAM_RETRIES`, resume from `mResumePts`
- Graceful degradation: overlay disabled if OSD libs fail; software encode if HW unavailable