1. DirectShow - a technical introduction
Qiming Lu / ATG - Video
Nov/22/2006
(It takes 2 hrs…)

2. Who Am I?
陆其明 / Qiming Lu
Graduated from Nanjing University in 2000, majoring in E.E.
Over 7 years of VC++ experience and over 6 years of multimedia experience
Awarded as a Microsoft Most Valuable Professional (MVP) for 3 times since 2004
My profile on Microsoft website:
4 books have been published: DirectShow Developing Tutorial (Tsinghua University Press, 2003), DirectShow Applications (Science Press, 2004), Windows Media Programming Guide (Tsinghua University Press, 2005), A Practical Guide to Script-Driven Software Development (Tsinghua University Press, 2006)
《DirectShow开发指南》《DirectShow实务精选》《Windows Media编程导向》《脚本驱动的应用软件开发方法与实践》
Joined Sonic on Apr/1, Working on HD DVD Player now…

3. Agenda
Overview of DirectShow
Basic Concepts of DirectShow
Tips on DirectShow Development
Tips on Learning DirectShow
New Updates of DirectShow
Demo & Homework
Q&A

4. Overview of DirectShow
DirectShow is a set of APIs to enable multimedia application development
DirectShow is a COM-based SDK
DirectShow is only available on Windows (including Windows CE)
DirectShow was a member of DirectX
DirectX = DirectSound + DirectDraw + Direct3D + DirectShow + DirectInput + DirectPlay + …
What can we do using DirectShow?
Audio / Video capture
Watch / Record TV on PC
Media file playback
Streaming media playback
DVD playback
Video editing / transcoding

5. Overview of DirectShow
System Architecture

6. Basic Concepts of DirectShow
So many concepts (Filter / Pin / Filter Graph / Media Type / Intelligent Connect / Push / Pull / Sample / Quality Control / Media Seeking / DMO…)
Let’s talk about…
Filter (basic interface: IBaseFilter)
is a kind of COM component
is a basic / minimum functional unit
must be added to a filter graph
must be connected to other filter(s)
has one or more pins
has 3 states: stopped, paused, running
has 3 basic types: source, transform, renderer
must be registered before being used in most cases
Pin (basic interface: IPin)
acts as a window of Filter
has a direction: either Input or Output
has one or more preferred media types
connection: upstream filter’s output pin  downstream filter’s input pin
Filter Graph (manager interface: IFilterGraph, IGraphBuilder, IVideoWindow, IMediaSeeking…)
is constructed with some specific purpose
is a container / manager for filters
looks like:

7. Basic Concepts of DirectShow
Media Type
typedef struct _MediaType {
GUID majortype;
GUID subtype;
BOOL bFixedSizeSamples;
BOOL bTemporalCompression;
ULONG lSampleSize;
GUID formattype;
IUnknown *pUnk;
ULONG cbFormat;
[size_is(cbFormat)] BYTE *pbFormat;
} AM_MEDIA_TYPE;
Major Type (MEDIATYPE_Video, MEDIATYPE_Audio, MEDIATYPE_Stream…)
Sub Type (MEDIASUBTYPE_YUY2, MEDIATYPE_RGB32, MEDIATYPE_PCM…)
Format Type (FORMAT_MPEGVideo, FORMAT_VideoInfo, FORMAT_WaveFormatEx…)
Format Details (pbFormat): is a structure of MPEG1VIDEOINFO or VIDEOINFOHEADER or WAVEFORMATEX, and determined by Format Type
Pin Connection / Intelligent Connect
always from an output pin to an input pin
is a process of media type negotiation between peer pins (please read the implementation codes of CBasePin::AgreeMediaType and CBasePin::TryMediaTypes)
basically uses the API: IFilterGraph::ConnectDirect(IPin *ppinOut, IPin *ppinIn, const AM_MEDIA_TYPE *pmt)
Intelligent Connect – easy to use, but please be aware and be careful!!!
IGraphBuilder::AddSourceFilter, IGraphBuilder::RenderFile, IGraphBuilder::Render, IGraphBuilder::Connect

8. Basic Concepts of DirectShow
Data Flow & Sample
Two modes: Push vs. Pull
Sample is a wrapper for media data and meta data
Basic interface: IMediaSample (GetPointer, SetTime, GetTime…)
Virtual Source Filter

9. Basic Concepts of DirectShow
AV Sync / Timestamp / Quality Control
AV Sync is basically achieved by timestamp and reference clock
Timestamp is carried by media samples, including startTime & endTime
IMediaSample::SetTime / GetTime
measured by REFERENCE_TIME, uses 10-7 s as the unit
Quality Control is a mechanism to improve total playback experience
Media Seeking (basic interface: IMediaSeeking)
is a way to play media content at a random position
is a way to know the status of playback
DirectX Media Objects
is light-weighted component for multimedia data processing
more flexible than filters, but NOT the replacement of filters
Microsoft suggests re-writing some transform filters to DMOs, e.g. Codec

10. Tips on DirectShow Development
Be aware of what you really want to make…
Tips on DShow Filter Development
Refer to some SDK filter samples
Choose a proper parent for your filter (CSource? CTransformFilter? CTransInPlaceFilter? CBaseVideoRenderer? CBaseFilter?)
Separate the commercial logic from the filter framework
Tips on DShow Application Development
Refer to some SDK application samples
Try to build your filter graph using Graphedt.exe first if possible
Register your application-created filter graph to ROT for debugging purpose
A DShow Filter?
A DShow Application?

11. Tips on Learning DirectShow
If you’re writing a DShow application, get some general knowledge of COM
If you’re writing a DShow filter, be sure to learn more details about COM
If you want to be an expert, read all base classes delivered with DShow SDK
SDK documentations and samples are always a good reference
Reading sample codes is a good point to start, but practice is more important
Be patient! You can’t do well in DirectShow in couples of days
Understand DirectShow to understand the principles of multimedia processing
Be ready to share your experience with others when you’re experienced

12. New Updates of DirectShow
DirectShow is NOT a member of DirectX any more
The latest version of DirectX is 9.0, and the next version is 10.0
DirectX 10 only works with Windows Vista, and can’t be installed onto Windows XP
Windows Vista initially integrates DirectX 9
DirectShow is good, but NOT good enough…
Filter is heavy-weighted and complicated
Filter can’t be used outside filter graph
The topology of filter graph is static, and not easy to change
The filter graph isn’t flexible enough to enable dynamic media type changing
DirectShow doesn’t provide a protected environment for media content
DirectShow doesn’t support playlist
DirectShow Editing Services is not flexible, and not easy to extend
Windows Media Foundation will be a replacement of DirectShow
WMF begins to be available on Windows Vista
WMF currently focuses on
Content Protection
Audio and Video Quality
DRM Interoperability

13. New Updates of DirectShow
The Lifecycle of DirectShow & WMF

14. Demo & Homework Demo: How to Use Graphedt.exe Find a filter you want
Register / Unregister a filter
Add filters to the filter graph and connect them one another
Playback control: Run / Pause / Stop / Seek
A useful tool: Filter Tracer
Review application-created filter graph(s)
Review Windows-Media-Player-created filter graph(s)
Homework: Write a simple media player
It’s a console application. Command line: myplayer c:\test.mpg
As for code lines, the less, the better
You can refer to SDK sample: PlayWnd

15. Q&A
Thank You!