Mastering the Adobe ActionScript 3.0 Dynamic Streaming Class: A Practical Guide

Troubleshooting Common Issues with the ActionScript 3.0 Dynamic Streaming Class

1. Stream won’t start or connect

• Check netConnection URL: Ensure the NetConnection URL exactly matches the media server or CDN endpoint (including rtmp/rtmpe/rtmfp or http(s) for progressive/HDS/HLS).
• Firewall/ports: Verify required ports (RTMP default 1935) are open on client/network and server accepts connections.
• Security sandbox: For Flash Player, confirm crossdomain.xml on the server allows the client domain.
• Event listeners: Listen for NetConnection events (NetStatusEvent.NET_STATUS, SecurityErrorEvent, IOErrorEvent) and log codes/messages.

2. Playback stalls or buffers too often

• Bitrate switching settings: Verify Dynamic Streaming class bitrate thresholds and buffer time are reasonable for target networks.
• Initial buffer length: Increase initial bufferTime to reduce startup stalls; lower bufferTime for low-latency use cases.
• Bandwidth estimation: Confirm the bandwidth measurement routine is enabled and working; false low estimates cause unnecessary downshifts.
• Server-side limits: Ensure the server can deliver required throughput; check server CPU/network saturation.

3. Incorrect bitrate selection or frequent oscillation

• Quality switch hysteresis: Implement or tune hysteresis to avoid rapid up/down switching (e.g., require sustained better bandwidth before upswitch).
• Accurate metrics: Use smoothed bandwidth averages and consider segment download times rather than single-sample reads.
• Manifest/stream metadata: Confirm the stream/manifest advertises correct bitrate values and segment durations.

4. Audio/video out of sync after switches

• Keyframe alignment: Ensure encoded segments have frequent keyframes and aligned GOP structures across bitrates to enable clean switches.
• Switch timing: Only switch at segment/keyframe boundaries. Verify the Dynamic Streaming class honors keyframe timestamps.
• Buffer handling: Flush or realign playback buffer on switch if timestamp discontinuities occur.

5. Seek or scrub issues

• Seekable ranges: Confirm server supports seeking and provides accurate metadata (duration/keyframe index).
• Progressive vs segmented: Differentiate progressive HTTP vs fragmented streaming—seeking behavior differs; use appropriate APIs.
• Index availability: For accurate seeks, ensure keyframe/index files are present and referenced.

6. Security/authorization failures

• Tokenized URLs: If using signed URLs or tokens, ensure tokens are valid, have correct TTL, and are included in both manifest and chunk requests.
• CORS/crossdomain: For HTTP-based streaming, check CORS headers; for Flash, verify crossdomain.xml permissions.
• ACLs/geo-blocking: Confirm server-side ACLs aren’t blocking clients.

7. Errors and exceptions to monitor

• NetStream.Play.StreamNotFound: Wrong stream name or missing file.
• NetStream.Play.Start / NetStream.Play.Stop: Use as cues for playback lifecycle.
• IOErrorEvent / SecurityErrorEvent: Network/file access or security policy issues.
• Custom error codes: Log and map any vendor/server-specific error codes.

8. Diagnostic steps and tools

• Verbose logging: Enable detailed NetConnection/NetStream logs and measure segment download times, buffer levels, and bitrate switches.
• Packet capture: Use Wireshark to inspect RTMP/HTTP requests and bandwidth utilization.
• Encoding checks: Validate encoded profiles, GOP size, bitrates, and keyframe intervals with ffprobe or MediaInfo.
• Server logs: Inspect media server/CDN logs for rejected requests, throttling, or errors.

9. Quick checklist to resolve common problems

1. Verify URLs and stream names.
2. Confirm server availability and ports.
3. Check crossdomain/CORS and security tokens.
4. Enable and inspect NetStatus and error events.
5. Tune bufferTime and switching hysteresis.
6. Ensure aligned keyframes across renditions.
7. Monitor server capacity and CDN behavior.

If you want, I can convert this into a troubleshooting flowchart, add example ActionScript code for logging NetStream/NetConnection events, or review specific NetStatus codes you’re seeing.