[PR #368] [MERGED] fix: add VBV buffer constraints and improve UDP streaming #427

New issue

Closed

opened 2026-10-15 13:00:29 +00:00 by bsakaguchi · 0 comments

bsakaguchi commented

2026-10-15 13:00:29 +00:00

Owner

📋 Pull Request Information

Original PR: https://github.com/games-on-whales/wolf/pull/368
Author: @Baz00k
Created: 3/13/2026
Status: ✅ Merged
Merged: 4/9/2026
Merged by: @ABeltramo

Base: stable ← Head: fix/streaming-improvements

📝 Commits (10+)

68fc791 feat: implement Apollo-style batched UDP send for video streaming
9f80199 feat: add packet pacing to prevent client buffer overflow
0bf85cb fix: add VBV buffer constraints to prevent frame size spikes
0157c58 refactor: move batched_send to src/core platform abstraction layer
ac5d357 fix: add config v7 with VBV encoder constraints and revert v3-v6
c0fc08a Committing clang-format changes
ed2b0aa chore: add comments explaining values
9f373b6 feat: add env config for pacing
5dacc0b feat: add migration to v7 config
91ed52f refactor: consolidate config migrations

📊 Changes

15 files changed (+1170 additions, -79 deletions)

View changed files

📝 src/core/CMakeLists.txt (+2 -0)
➕ src/core/src/core/batched_send.hpp (+104 -0)
➕ src/core/src/platforms/linux/batched_send/batched_send.cpp (+233 -0)
➕ src/core/src/platforms/unknown/batched_send.cpp (+19 -0)
📝 src/moonlight-server/CMakeLists.txt (+1 -1)
📝 src/moonlight-server/gst-plugin/gstrtpmoonlightpay_video.cpp (+2 -2)
📝 src/moonlight-server/rtsp/commands.hpp (+4 -2)
📝 src/moonlight-server/state/configTOML.cpp (+20 -16)
📝 src/moonlight-server/state/default/config.include.toml (+15 -12)
➕ src/moonlight-server/state/default/config.v7.toml (+562 -0)
📝 src/moonlight-server/state/serialised_config.hpp (+1 -1)
📝 src/moonlight-server/streaming/streaming.cpp (+160 -43)
📝 tests/CMakeLists.txt (+2 -1)
📝 tests/assets/config.test.toml (+1 -1)
➕ tests/testBatchedSend.cpp (+44 -0)

📄 Description

Summary

Fix streaming instability on clients with limited receive buffers (e.g. Moonlight-TV on embedded devices) and Wolf ignoring client bitrate settings.
Changes in this PR allowed me to go from unstable 12mbit stream with significant packet loss to full, stable 35mbit on my TV. This should also stabilize streaming over Wi-Fi.

Root cause: Missing VBV (Video Buffering Verifier) buffer constraints on all hardware encoder pipelines. Without VBV, CBR mode allows individual frames — especially IDR frames and complex game scenes — to spike 2-5x the per-frame bitrate budget, overwhelming client receive buffers.

Most of this code is just reimplementation of what alredy exists in Sunshine/Apollo.

Changes

1. Apollo-style batched UDP send

Replace async single-packet async_send_to() calls with synchronous batched sends using sendmmsg()
Add platform abstraction layer (batched_send.hpp/cpp) with Linux implementation
Configure socket QoS and buffer sizes optimized for streaming workloads
Increase default video packet payload size to match Moonlight protocol spec

2. Packet pacing

Add rate-limited packet pacing for video UDP sends (80% of 1Gbps link speed)
Sub-millisecond sleep-based scheduling between send windows
Smooths out large frame bursts that would could otherwise overwhelm low-powered devices

3. VBV buffer constraints for all encoders

NVIDIA (nvcodec): Add vbv-buffer-size to all nvh265enc, nvh264enc, nvav1enc pipelines (config v3-v6 + include)
VAAPI (va): Fix rate-control from cqp (Constant QP — ignores bitrate entirely) to cbr, and fix cpb-size from {bitrate} (1-second buffer) to single-frame buffer
VBV buffer size computed as bitrate_kbps / refreshRate (one frame's worth), matching Sunshine/Apollo's approach

Fixes #332

Testing

Tested on Moonlight-TV at 35 Mbps AV1 with stable streaming (previously broke above 12 Mbps).
Streaming still works on original Moonlight and Artemis clients (tested on S23 Ultra and M1 Mac).

Files Changed

streaming/streaming.cpp — Batched send, pacing, VBV format arg
platform/batched_send.{hpp,cpp} — New batched send abstraction
platform/linux/batched_send.cpp — Linux sendmmsg implementation
gstrtpmoonlightpay_video.cpp, rtsp/commands.hpp — Packet size
config.include.toml, config.v3-v6.toml — Encoder pipeline fixes

_{🔄 This issue represents a GitHub Pull Request. It cannot be merged through Gitea due to API limitations.}

## 📋 Pull Request Information **Original PR:** https://github.com/games-on-whales/wolf/pull/368 **Author:** [@Baz00k](https://github.com/Baz00k) **Created:** 3/13/2026 **Status:** ✅ Merged **Merged:** 4/9/2026 **Merged by:** [@ABeltramo](https://github.com/ABeltramo) **Base:** `stable` ← **Head:** `fix/streaming-improvements` --- ### 📝 Commits (10+) - [`68fc791`](https://github.com/games-on-whales/wolf/commit/68fc79177bd19ed2afe85cfba76c1fc887ef93d9) feat: implement Apollo-style batched UDP send for video streaming - [`9f80199`](https://github.com/games-on-whales/wolf/commit/9f80199dc2d72c3b4618ca84b1bb93725bd91b7c) feat: add packet pacing to prevent client buffer overflow - [`0bf85cb`](https://github.com/games-on-whales/wolf/commit/0bf85cb92c5a4025bd6b0cc53dac7b4ee71a70ba) fix: add VBV buffer constraints to prevent frame size spikes - [`0157c58`](https://github.com/games-on-whales/wolf/commit/0157c5821208040be8c3225441997b475f2be7c8) refactor: move batched_send to src/core platform abstraction layer - [`ac5d357`](https://github.com/games-on-whales/wolf/commit/ac5d3578ab6041d4cd086075f41f383d4450248d) fix: add config v7 with VBV encoder constraints and revert v3-v6 - [`c0fc08a`](https://github.com/games-on-whales/wolf/commit/c0fc08a7c5d6ec110b5fd5fbf925707361d13945) Committing clang-format changes - [`ed2b0aa`](https://github.com/games-on-whales/wolf/commit/ed2b0aa5bfbda738b7539e435b0e49289318dd3b) chore: add comments explaining values - [`9f373b6`](https://github.com/games-on-whales/wolf/commit/9f373b60c3d01ee39b3f7fd7d81b01bba6c59f8f) feat: add env config for pacing - [`5dacc0b`](https://github.com/games-on-whales/wolf/commit/5dacc0bcdd06b1aee25b3a94370ee4b81c9887df) feat: add migration to v7 config - [`91ed52f`](https://github.com/games-on-whales/wolf/commit/91ed52f49efe0e72c26266b7c9cc01979f58005a) refactor: consolidate config migrations ### 📊 Changes **15 files changed** (+1170 additions, -79 deletions) <details> <summary>View changed files</summary> 📝 `src/core/CMakeLists.txt` (+2 -0) ➕ `src/core/src/core/batched_send.hpp` (+104 -0) ➕ `src/core/src/platforms/linux/batched_send/batched_send.cpp` (+233 -0) ➕ `src/core/src/platforms/unknown/batched_send.cpp` (+19 -0) 📝 `src/moonlight-server/CMakeLists.txt` (+1 -1) 📝 `src/moonlight-server/gst-plugin/gstrtpmoonlightpay_video.cpp` (+2 -2) 📝 `src/moonlight-server/rtsp/commands.hpp` (+4 -2) 📝 `src/moonlight-server/state/configTOML.cpp` (+20 -16) 📝 `src/moonlight-server/state/default/config.include.toml` (+15 -12) ➕ `src/moonlight-server/state/default/config.v7.toml` (+562 -0) 📝 `src/moonlight-server/state/serialised_config.hpp` (+1 -1) 📝 `src/moonlight-server/streaming/streaming.cpp` (+160 -43) 📝 `tests/CMakeLists.txt` (+2 -1) 📝 `tests/assets/config.test.toml` (+1 -1) ➕ `tests/testBatchedSend.cpp` (+44 -0) </details> ### 📄 Description ## Summary Fix streaming instability on clients with limited receive buffers (e.g. Moonlight-TV on embedded devices) and Wolf ignoring client bitrate settings. Changes in this PR allowed me to go from unstable 12mbit stream with significant packet loss to full, stable 35mbit on my TV. This should also stabilize streaming over Wi-Fi. **Root cause**: Missing VBV (Video Buffering Verifier) buffer constraints on all hardware encoder pipelines. Without VBV, CBR mode allows individual frames — especially IDR frames and complex game scenes — to spike 2-5x the per-frame bitrate budget, overwhelming client receive buffers. Most of this code is just reimplementation of what alredy exists in Sunshine/Apollo. ## Changes ### 1. Apollo-style batched UDP send - Replace async single-packet `async_send_to()` calls with synchronous batched sends using `sendmmsg()` - Add platform abstraction layer (`batched_send.hpp/cpp`) with Linux implementation - Configure socket QoS and buffer sizes optimized for streaming workloads - Increase default video packet payload size to match Moonlight protocol spec ### 2. Packet pacing - Add rate-limited packet pacing for video UDP sends (80% of 1Gbps link speed) - Sub-millisecond sleep-based scheduling between send windows - Smooths out large frame bursts that would could otherwise overwhelm low-powered devices ### 3. VBV buffer constraints for all encoders - **NVIDIA (nvcodec)**: Add `vbv-buffer-size` to all `nvh265enc`, `nvh264enc`, `nvav1enc` pipelines (config v3-v6 + include) - **VAAPI (va)**: Fix `rate-control` from `cqp` (Constant QP — ignores bitrate entirely) to `cbr`, and fix `cpb-size` from `{bitrate}` (1-second buffer) to single-frame buffer - VBV buffer size computed as `bitrate_kbps / refreshRate` (one frame's worth), matching Sunshine/Apollo's approach ## Related issues Fixes #332 ## Testing Tested on Moonlight-TV at 35 Mbps AV1 with stable streaming (previously broke above 12 Mbps). Streaming still works on original Moonlight and Artemis clients (tested on S23 Ultra and M1 Mac). ## Files Changed - `streaming/streaming.cpp` — Batched send, pacing, VBV format arg - `platform/batched_send.{hpp,cpp}` — New batched send abstraction - `platform/linux/batched_send.cpp` — Linux sendmmsg implementation - `gstrtpmoonlightpay_video.cpp`, `rtsp/commands.hpp` — Packet size - `config.include.toml`, `config.v3-v6.toml` — Encoder pipeline fixes --- <sub>🔄 This issue represents a GitHub Pull Request. It cannot be merged through Gitea due to API limitations.</sub>

bsakaguchi

2026-10-15 13:00:29 +00:00