Troubleshooting FLVRecorder: Common Issues and FixesFLVRecorder is a tool many developers and stream operators use to capture, store, and manage FLV-format video streams. Despite its usefulness, users can encounter a range of problems — from configuration mistakes and codec mismatches to network instability and file corruption. This article walks through common FLVRecorder issues, how to diagnose them, and practical fixes you can apply to restore reliable recording and playback.
1. Recording fails to start
Symptoms:
- No output FLV file created.
- FLVRecorder process exits immediately or shows an error.
- UI shows “recording” but file size remains 0 bytes.
Common causes & fixes:
- Incorrect input source (camera/stream) specified: Verify the input URL or device name. If capturing from an RTMP/HTTP stream, paste the URL into a browser or VLC to confirm accessibility.
- Missing or wrong permissions: Ensure the recorder has read permission for input devices (e.g., /dev/video*) and write permission in the output directory.
- Port or protocol mismatch: For RTMP sources, confirm protocol (rtmp vs rtmps) and port (usually 1935). If your server requires TLS, switch to rtmps or enable TLS in recorder settings.
- Command-line or configuration syntax error: Re-check config files and command flags for typos. Run the recorder with verbose or debug logging enabled to reveal parsing errors.
2. Output file is created but is empty or very small
Symptoms:
- FLV file exists but is 0 bytes or only a few KB.
- Player fails to open the file or reports “unsupported format.”
Common causes & fixes:
- No data arriving from source: Inspect network connectivity and source health. Use tools like tcpdump/wireshark or curl to verify data flow.
- Input format mismatch: If the source provides fragmented MP4/HLS or another container, FLVRecorder may not accept it directly. Transcode/convert the incoming stream to FLV-compatible codecs (H.264 for video, AAC/MP3 for audio) or use an intermediary tool (FFmpeg) to repackage.
- Recorder terminated unexpectedly: Check system logs and recorder logs for crashes, OOM (out-of-memory), or killed-by-OOM-killer messages. Increase memory limits or adjust other processes.
- Disk quota or filesystem limits: Confirm sufficient disk space and that the filesystem supports large files. If using network mounts (NFS/SMB), ensure stability and permissions.
3. Corrupted FLV file or playback errors
Symptoms:
- Players show “file corrupted” or playback stops after a few seconds.
- Seeking within the file fails or shows artifacts.
Common causes & fixes:
- Abrupt termination during write: Always try to stop recording cleanly so the FLV header/footer is finalized. If crash is unavoidable, try using a repair tool (e.g., FFmpeg) to rebuild the container:
ffmpeg -i broken.flv -c copy repaired.flv - Incorrect timestamps or metadata: Some recorders produce bad timestamps when input stream has TV/clock discontinuities. Re-mux with FFmpeg to regenerate timestamps:
ffmpeg -fflags +genpts -i input.flv -c copy output.flv - Bad codec stream inside FLV: Play the file with verbose logging in FFmpeg to check codec errors:
ffmpeg -v error -i input.flv -f null -If codecs are unsupported or malformed, transcode to known-good codecs:
ffmpeg -i input.flv -c:v libx264 -c:a aac -strict -2 fixed.flv
4. Audio/video out of sync
Symptoms:
- Lip sync drift or persistent offset between audio and video.
- Sync worsens over long recordings.
Common causes & fixes:
- Variable input frame rates: Force a stable frame rate on input or re-encode with a fixed frame rate:
ffmpeg -i input.flv -r 30 -c:v libx264 -c:a copy output.flv - Incorrect timestamp handling by FLVRecorder: Enable timestamp correction or use the -fflags +genpts option when remuxing with FFmpeg.
- Clock drift between sources (e.g., separate audio/video encoders): Use a single synchronized capture source or re-sync in post by shifting audio with:
ffmpeg -i input.flv -itsoffset 0.2 -i input.flv -map 0:v -map 1:a -c copy synced.flv(Adjust 0.2 to the needed offset; negative offsets are allowed.)
- Encoding latency from hardware encoders: Lower buffering or use software encoders for consistent timing.
5. High CPU / memory usage during recording
Symptoms:
- System slows or becomes unresponsive while recording.
- Recorder process consumes excessive CPU or RAM.
Common causes & fixes:
- Software encoding at high resolutions: Use hardware acceleration (NVENC, QuickSync, VAAPI) if available, or lower output resolution/frame-rate/bitrate.
- Excessive logging or debug mode: Disable verbose logs in production.
- Multiple simultaneous streams: Balance load across machines or use a dedicated capture server.
- Memory leak in recorder: Monitor process memory over time (top/htop). If it grows without bound, update FLVRecorder to latest release or use periodic restarts as a temporary mitigation.
6. Network-related issues (stalls, dropped frames)
Symptoms:
- Frames dropped, stuttering, or gaps in recorded files.
- Recording stops when network fluctuates.
Common causes & fixes:
- Unreliable network: Use local buffering (disk or RAM) and implement reconnect/retry logic. If FLVRecorder supports segment buffering, enable it and mount fast local storage (SSD).
- Bandwidth insufficient: Reduce bitrate, resolution, or use a variable bitrate (VBR) profile.
- Latency and packet loss: Use UDP-to-TCP fallback if available (or vice versa), or deploy error correction like FEC at transport level. For RTMP, ensure TCP is stable; for RTSP/UDP use RTP over TCP as fallback.
- Intermediary proxies/firewalls dropping connections: Whitelist streaming ports and IPs; increase keepalive intervals.
7. Authentication and authorization errors
Symptoms:
- “401 Unauthorized”, “403 Forbidden”, or authentication prompts.
- Recorder logs show authentication failures.
Common causes & fixes:
- Wrong credentials or tokens: Verify API keys, usernames, and passwords. For expiring tokens, implement refresh logic or use long-lived credentials if secure.
- Time-skew with signed URLs: Ensure server and recorder clocks are synchronized (NTP).
- IP restrictions on the streaming server: Whitelist recorder’s outbound IP or use secure tunnels.
- SSL/TLS certificate issues: If using rtmps or HTTPS endpoints, ensure recorder trusts the server certificate (install CA bundle or disable strict verification only as a last resort).
8. Incorrect file naming or rotation problems
Symptoms:
- Output files overwrite each other or use unexpected names.
- Rotation doesn’t occur at expected intervals.
Common causes & fixes:
- Misconfigured naming templates: Check timestamp and unique-id variables in naming templates. Use safe tokens like %Y-%m-%d_%H-%M-%S.
- Timezone vs UTC mismatch: Ensure naming uses the expected timezone; prefer UTC for predictability.
- Permissions preventing rotation: Recorder may be unable to create new files due to permissions or directory limits.
- Post-processing scripts failing: If rotation triggers external scripts, add logging and error handling so failures don’t break rotation.
9. Integrations (CDN, archive systems) fail after recording
Symptoms:
- Uploads to CDN fail or files missing in archive.
- Transcoding pipelines error out when consuming FLV files.
Common causes & fixes:
- Unsupported container specifics: Some CDNs expect MP4 or fragmented MP4; convert FLV to MP4 for compatibility:
ffmpeg -i input.flv -c copy output.mp4 - Transfer method mismatches (SCP vs API): Match the upload method the CDN expects and test with a single file manually first.
- Missing metadata: Some pipelines rely on metadata (duration, codecs) being present. Re-muxing often fixes this.
- Rate limits on API endpoints: Implement retries with exponential backoff.
10. Security concerns (exposed streams, insecure storage)
Symptoms:
- Unauthorized access to recorded FLV files.
- Sensitive streams stored without encryption.
Common causes & fixes:
- Weak or missing access controls: Use strong authentication on storage and streaming endpoints.
- Unencrypted storage: Encrypt files at rest or store on encrypted volumes.
- Publicly accessible URLs: Use signed URLs or short-lived tokens for downstream access.
- Local copies on shared machines: Restrict disk access and purge temporary files.
Diagnostic checklist (quick)
- Confirm input stream plays in VLC/FFmpeg.
- Check recorder logs with highest available verbosity.
- Verify disk space, permissions, and filesystem health.
- Test remux/repair with FFmpeg commands shown above.
- Monitor system resources (CPU, memory, network) during recording.
- Validate credentials, TLS certificates, and time synchronization.
- Reproduce issue with a minimal configuration (single source, local disk).
Useful FFmpeg commands (summary)
- Repair/remux:
ffmpeg -i broken.flv -c copy repaired.flv - Regenerate timestamps:
ffmpeg -fflags +genpts -i input.flv -c copy output.flv - Transcode to fixed codecs:
ffmpeg -i input.flv -c:v libx264 -c:a aac fixed.flv - Convert FLV to MP4:
ffmpeg -i input.flv -c copy output.mp4
Preventive best practices
- Use monitored, redundant capture infrastructure for mission-critical recording.
- Standardize on supported codecs (H.264 + AAC/MP3) and stable frame rates.
- Keep FLVRecorder and related libraries up to date.
- Implement automated post-recording checks (file integrity, playback test).
- Keep detailed logs and alerts for failures, disk thresholds, and resource exhaustion.
If you can share specific error messages, log excerpts, or your FLVRecorder configuration, I can provide targeted commands and configuration changes to resolve the issue.
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