98 lines
2.8 KiB
Markdown
98 lines
2.8 KiB
Markdown
# Operational Caveats
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This document captures the current runtime constraints for `cvmmap-streamer` after the FFmpeg-only cleanup.
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## Input Model
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### cvmmap URI Only
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The runtime ingests from a cvmmap URI, for example:
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```bash
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./build/cvmmap_streamer --run-mode pipeline --input-uri 'cvmmap://zed@/tmp/cvmmap'
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```
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Legacy flags such as `--shm-name`, `--zmq-endpoint`, `--input-mode`, and the dummy-input options are no longer supported.
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## Encoder Path
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### FFmpeg Is The Only Encoder Backend
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The public backend surface is:
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- `--encoder-backend auto`
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- `--encoder-backend ffmpeg`
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Both resolve to the FFmpeg encoder path. The removed GStreamer backend is no longer available.
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### NVENC Is Optional
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When `--encoder-device nvidia` is selected, FFmpeg must expose `h264_nvenc` and `hevc_nvenc`.
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Useful local checks:
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```bash
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ffmpeg -hide_banner -encoders | rg 'nvenc|libx264|libx265'
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```
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If NVENC is unavailable, use:
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```bash
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--encoder-device software
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```
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### Low-Latency Defaults
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The current low-latency defaults are:
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- `gop=30`
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- `b_frames=0`
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- NVENC preset/tune tuned for low latency
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This favors immediacy over compression efficiency.
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## Transport Caveats
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### RTMP Is Enhanced RTMP Only
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The repo now supports:
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- `libavformat` RTMP output
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- `ffmpeg_process` RTMP output
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The removed custom RTMP packetizer and `domestic` mode are no longer available. RTMP is always Enhanced RTMP.
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### RTP SDP Is Optional
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The RTP publisher can write an SDP sidecar when `--rtp-sdp` is set. This is only for generic receivers that need an out-of-band description. If the consumer is preconfigured, skip the SDP output.
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### No Direct RTSP/WebRTC Publishing
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This repo does not contain a direct RTSP publisher or a direct WebRTC/WHEP publisher.
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If you want browser playback or WHEP, publish RTMP to a media server such as SRS and let that server expose WHEP/WebRTC.
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## Media Scope
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### No Audio Support
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This project is video-only. It publishes or records encoded video access units only.
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If you need audio transport, muxing, or A/V sync, that is outside the current repo scope.
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## Recording Caveats
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### MCAP Stores Encoded Video Frames
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MCAP recording stores one `foxglove.CompressedVideo` message per encoded access unit. Replay depends on encoded keyframes carrying decoder configuration; this is handled by the current writer on keyframes.
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## External Server Caveats
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### Local SRS Defaults Can Hit `ulimit`
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On this machine, stock SRS configs can fail at startup if `max_connections` exceeds the local `ulimit -n`. The checked-in smoke profile uses `max_connections 64` to avoid that local failure mode.
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### Server Latency Still Matters
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Low encoder latency does not guarantee low end-to-end latency. SRS, ZLMediaKit, HTTP-FLV players, and browser buffering can all add delay on top of the encoder path.
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