for issue #4418, #4151, #4076 .DVR Missing First Few Seconds of
Audio/Video
### Root Cause
When recording WebRTC streams to FLV files using DVR, the first 4-6
seconds of audio/video are missing. This occurs because:
1. **Packets are discarded before A/V sync is available**: The
RTC-to-RTMP conversion pipeline actively discards all RTP packets when
avsync_time <= 0.
2. **Original algorithm requires 2 RTCP SR packets**: The previous
implementation needed to receive two RTCP Sender Report (SR) packets
before it could calculate the rate for audio/video synchronization
timestamp conversion.
3. **Delay causes packet loss**: Since RTCP SR packets typically arrive
every 2-3 seconds, waiting for 2 SRs means 4-6 seconds of packets are
discarded before A/V sync becomes available.
4. **Audio SR arrives slower than video SR**: As reported in the issue,
video RTCP SR packets arrive much faster than audio SR packets. This
asymmetry causes audio packets to be discarded for a longer period,
resulting in the audio loss observed in DVR recordings.
### Solution
1. **Initialize rate from SDP**: Use the sample rate from SDP (Session
Description Protocol) to calculate the initial rate immediately when the
track is created.
Audio (Opus): 48000 Hz → rate = 48 (RTP units per millisecond)
Video (H.264/H.265): 90000 Hz → rate = 90 (RTP units per millisecond)
2. **Enable immediate A/V sync:** With the SDP rate available,
cal_avsync_time() can calculate valid timestamps from the very first RTP
packet, eliminating packet loss.
3. **Smooth transition to precise rate**: After receiving the 2nd RTCP
SR, update to the precisely calculated rate based on actual RTP/NTP
timestamp mapping.
## Configuration
Added new configuration option `init_rate_from_sdp` in the RTC vhost
section:
```nginx
vhost rtc.vhost.srs.com {
rtc {
# Whether initialize RTP rate from SDP sample rate for immediate A/V sync.
# When enabled, the RTP rate (units per millisecond) is initialized from the SDP
# sample rate (e.g., 90 for video 90kHz, 48 for audio 48kHz) before receiving
# 2 RTCP SR packets. This allows immediate audio/video synchronization.
# The rate will be updated to a more precise value after receiving the 2nd SR.
# Overwrite by env SRS_VHOST_RTC_INIT_RATE_FROM_SDP for all vhosts.
# Default: off
init_rate_from_sdp off;
}
}
```
**⚠️ Important Note**: This config defaults to **off** because:
- ✅ When **enabled**: Fixes the audio loss problem (no missing first 4-6
seconds)
- ❌ When **enabled**: VLC on macOS cannot play the video properly
- ✅ Other platforms work fine (Windows, Linux)
- ✅ FFplay works fine on all platforms
Users experiencing audio loss in DVR recordings can enable this option
if they don't need VLC macOS compatibility. We're investigating the VLC
macOS issue to make this feature safe to enable by default in the
future.
---------
Co-authored-by: winlin <winlinvip@gmail.com>
Co-authored-by: OSSRS-AI <winlinam@gmail.com>
This PR renames the trunk/ide/ directory to trunk/cmake/ to better
reflect its actual purpose. The directory contains CMake build
configuration files used by multiple IDEs (CLion, VSCode), not
IDE-specific files.
* Directory rename: trunk/ide/ → trunk/cmake/
* Build output location: trunk/ide/vscode-build/ → trunk/cmake/build/
* CMakeLists.txt: Moved from trunk/ide/srs_clion/CMakeLists.txt to
trunk/cmake/CMakeLists.txt
SRS forward feature only supports plain RTMP protocol, not RTMPS (RTMP over SSL/TLS). This is by design - SRS SSL is server-side only (accepting connections), not client-side (initiating connections). The forward feature uses SrsSimpleRtmpClient which has no SSL handshake or encryption capabilities for outgoing connections.
Changes:
1. Add RTMPS URL detection in SrsForwarder::initialize()
2. Return ERROR_NOT_SUPPORTED error when RTMPS destination is detected
3. Add unit test to verify RTMPS URLs are properly rejected
4. Add FAQ section to .augment-guidelines explaining the limitation
For users who need to forward to RTMPS destinations (e.g., AWS IVS), the recommended solution is to use FFmpeg with SRS HTTP Hooks:
- on_publish event: Automatically start FFmpeg to relay stream to RTMPS destination
- on_unpublish event: Automatically stop FFmpeg process when stream ends
This provides a fully automated, production-ready RTMPS relay solution without adding complexity to SRS core.
Related: #4536
---------
Co-authored-by: OSSRS-AI <winlinam@gmail.com>
Regression since 20f6cd595c
The early code might meet bridge is empty when
there is no bridge(e.x. rtc to rtc). Then srs_freep will free the brige.
Remove this code that seems redundant.
---------
Co-authored-by: Jacob Su <suzp1984@gmail.com>
Signed-off-by: Jack Lau <jacklau1222@qq.com>
