Flash DirectShow Source Filter: Complete Setup and Configuration Guide

Flash DirectShow Source Filter: Integrating Flash Streams into DirectShow Pipelines

Overview

This article explains how a Flash DirectShow source filter works and shows a practical approach to integrating Flash (SWF/SWF-like) streams into DirectShow pipelines on Windows. It covers architecture, implementation steps, sample code patterns, threading and timing considerations, and guidance for handling codecs, synchronization, and error recovery.

When to use this filter

• You need to render or process Flash content (SWF or streamed Flash video) inside a DirectShow graph.
• You’re building a custom media player that must incorporate Flash-based streams alongside other media.
• You want to decode or capture Flash video/audio for recording, streaming, or post-processing via DirectShow filters.

Architecture and components

• Source Filter: Implements IFilterGraph, IBaseFilter, and related interfaces to provide media samples downstream.
• Output Pin(s): Provide media types (video and possibly audio) via IPin/IEnumPins; handle connection and media type negotiation.
• Sample Grabber / Renderer: Downstream components that accept samples (e.g., Sample Grabber, custom renderer).
• Flash Engine: The component or library that parses/decodes Flash content (could be Adobe Flash runtime, a third-party decoder, or a custom SWF parser/renderer).
• Threading & Scheduler: A worker thread to push samples downstream according to timestamps and DirectShow’s streaming model.
• Sync Clock: Use IMediaSeeking/IMediaPosition and reference clocks to maintain A/V sync.

Implementation steps (high-level)

1. Choose Flash handling approach
   • Use an existing Flash playback library (if licensing permits) or implement a SWF parser/renderer. For RTMP/FLV streams, use an FLV/RTMP demuxer + codec.
2. Create COM filter structure
   • Implement required COM interfaces: IBaseFilter, IUnknown, IPersist, IMediaSeeking (optional), and custom interfaces as needed.
3. Define media types
   • For video: AM_MEDIA_TYPE with subtype VIDEOINFOHEADER or VIDEOINFOHEADER2, set appropriate width, height, bitrate, and format (e.g., RGB24, RGB32, or compressed like H.264 if decoding).
   • For audio: WAVEFORMATEX with PCM or AAC/MP3 details if audio present.
4. Implement output pin(s)
   • Support Connect, Disconnect, QueryAccept, EnumMediaTypes, GetMediaType, and DecideBufferSize.
   • Provide negotiated media types based on Flash content capabilities.
5. Worker thread to deliver samples
   • Implement a run loop that reads frames from the Flash engine, wraps them in IMediaSample, sets timestamps (rtStart/rtStop), and calls IPin::Receive on downstream input pins or uses the connection’s allocator to deliver samples.
6. Timing and synchronization
   • Use the graph’s reference clock (IMediaFilter::GetSyncSource) for accurate timestamps.
   • Convert Flash frame timing (e.g., SWF frame rate) to REFERENCE_TIME units (100 ns).
7. Seeking and timestamps
   • Implement IMediaSeeking if random access is supported; otherwise support basic seeking semantics with start/stop.
8. Error handling and reconnection
   • Detect format changes and send EC_COMPLETE or ECERRORABORT events as needed via IMediaEventSink.
9. Registration and graph building
   • Register the filter DLL with COM and provide a DirectShow-friendly CLSID/SetupAPI information so GraphEdit/GraphStudio can use it.

cpp
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REFERENCE_TIME rtStart = frameIndex  frameDuration;
REFERENCETIME rtStop= rtStart + frameDuration;
pSample->SetTime(&rtStart, &rtStop);
pSample->SetActualDataLength(frameSize);

cpp
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HRESULT hr = m_pOutputPin->Deliver(pSample);
if (FAILED(hr)) { / handle downstream refusal or stop / }

cpp
Copy CodeCopied
if (pos == 0) {
  VIDEOINFOHEADER pVih = (VIDEOINFOHEADER)CoTaskMemAlloc(sizeof(VIDEOINFOHEADER));
  ZeroMemory(pVih, sizeof(VIDEOINFOHEADER));
  pVih->bmiHeader.biWidth = width;
  pVih->bmiHeader.biHeight = height;
  // set other fields…
  pmt->majortype = MEDIATYPE_Video;
  pmt->subtype   = MEDIASUBTYPE_RGB24;
  pmt->pbFormat  = (BYTE)pVih;
  pmt->cbFormat  = sizeof(VIDEOINFOHEADER);
  return S_OK;
}