1– Introduction To Direct Show

Introduction to
DirectShow - 1

Windows Media
Streaming Architecture

Fast Forward Your Development www.dsp-ip.com

Intel - Motivation & Goals

DirectShow is the most common architecture for:
• STB and IP-STB media streaming and broadcast
reception
• PC Streaming
Goals
• Understand STB architecture, its advantages and
disadvantages
• Fast prototyping and application building for
testing and demonstrations


What is DirectX
• DirectX is Microsoft's component based
architecture for media processing.
• Similar streaming architecture were designed by:
▫ Real
▫ Emblaze (RapidMedia)
▫ Linux (GStreaming)
• Media processing
▫ Audio
▫ Video
▫ Transport streams
▫ text.


DirectX – Why we need it?
• Software reusability
▫ Code blocks can be reused and inherited
▫ Common Interfaces
• Easy connection between 3rd party modules
• Which components?
▫ Compression
▫ color conversion
▫ audio effects
▫ Transport stream handlers


BACKGROUND

DirectX Evolution from proprietary Codec
to Filter base architecture


VFW
• VFW architecture – a Plug-In architecture
that supported CODEC and CAPTURE
Interfaces for Audio & Video stream
manipulation.
• Advantages – All the CODECs have the
same interfaces. There is no need specific
modifications for each codec IO Interfaces

Capture CODEC

Control Interfaces


VFW Problems
 Rigid architecture
 Only three types of filters
 How to add costume filters that split or mux
transport stream?
 Rigid interfaces creates a problem to the future
progress of the architecture


Active Movie
• A Filter base architecture that support customize
filters
• The architecture is built using:
▫ Filters that manipulates the stream
▫ Pins that handle filter connection
▫ graph management which
 Connect the filters (automatically)
 Manage filters states (run, pause, stop)
 Transfer messages between filters


DirectX
• Evolution of Active Movie (Audio & Video) to
other aspects:
▫ DirectShow – (previously ActiveMovie)
Audio/Video/Text.
▫ DirectDraw/Direct3D – Graphics.
▫ DirectSound – Sound effects and 3D sound.
▫ DirectPlay/DirectInput – Multiplayer Game tools.
▫ DirectMusic – Automatic music generation


INTRODUCTION TO DIRECTSHOW

Hands-on DirectShow : GraphEdit


GraphEdit

• Visual Interface for
graph building and
testing.


GraphEdt – Rendering a file
• Render a media file
• The graph build is what the OS does when you
double-click on a file.
• File rendering options:
▫ Drag a media file to graph edit
▫ Use File->Open File
▫ Use:
 graph->Insert filters use the circled button as a short cut
 Select File Source Async.
 Right click on output pin and select render


GraphEdt - Play with it
• Use the: Play, Pause, and Stop commands
▫ Notice the file progress bar

• Use the slider to change the current play
position


GraphEdit – A bit more
• Try looking at filter properties:
• Use right-click on the filter and select “Filter
Properties”
• We will later look at the Interface that enables
the communication to property pages.
• Example of Source file property
• This property is used only for monitoring and
not for controls. Why?


The Translator video
• Lets view it using Graphedt MediaMetargemet.wmv
• This video is a nice example for information processing
architecture
• The information is:
▫ Generated at the source (Keren)
▫ Processed and translated by a “transform unit” (Riki – translator)
▫ Rendered to the students
▫ Feedback messages are passed from the Renderer to the source
via the translator

Teacher
Info. Source

Smart Student Student
“Transform” “Renderer


DirectShow Basic ideas

• Information processing is a sequential process
• Each processing unit has a clear function
• The Source “Push” or pump information to
processing units (Blue). Data information is
always Unidirectional: “Downstream”
• Feedback is sent from the Renderer(s) to the
source (Orange) – “Upstream”
• No Information loops

Source

“Renderer
“Transform”

Information passing architecture
• There are basically two methods:
▫ Push
▫ Pull
• Those architecture differ in
▫ threading,
▫ Which filter is the active filter
▫ Where is the “Brain” of the graph


Push Architecture
• Source is active
• Source generate Media Samples
• information is pushed by the source
• Like in the case of the “Metargemet”
• Source is active, owns the “processing thread”
• Used in
▫ ASF/WMA/WMV files
▫ Video capture (USB cam, video cards)
▫ BDA capture


Pull Architecture
• Information is pulled by a non-source filter
• Source is passive
• Does not own the “processing thread”
• In most file processing schemes (AVI, MPEG2)
the source is “dumb” and passive and the parser
(demuxer) holds the “knowledge” of file parsing.


Components required
• Data Processing unit– used for:
▫ Media data Generation
▫ Media data manipulation/transform
▫ Media data rendering
• Interfaces – Generic Interfaces between data
processing units
▫ In “Metargemet” we use “Air Interface” with two basic
media descriptors
• Media descriptors
▫ In “Metargemet” we use two media types:
 Archaic speech media between Source and Transform
 “Sleng” between Transform (Riki) and Renderer (Student)
• Management unit (in “Translator” –
class/school)


Naming
• Data processing unit = Filter
▫ Used for data manipulation and transform.
• Filter Interface = Pin
▫ Used to define the connection between filters
▫ Include information about:
 Direction
 Memory required
 Media Type


Naming - 2
• Media Descriptor = Media Type
▫ Include information about the media passed
• Data Unit = Media Sample
▫ Include the data itself
▫ Include information about the data


Filters
• ActiveX objects
▫ (Use COM Interfaces)
• Manipulates data
• Have Pin as members for interfacing other filters
• Three basic types: Source, Render, Transform
• Identification: GUID
• Control – property pages


Pin
• Filters have one or more IO Interfaces - pins
• Pin is a class which basically holds interfaces to which
connect processing modules (filters)
• Pins could be exposed or hidden
▫ Look at Infinite Pin tee filter
▫ Dynamic creation of pins for many types of filters:
 Infinite Pin T
 MPEG and AVI Splitters
• Two basic type:
▫ Input
▫ Output


Graph Builder
• Create a streaming process for example:
▫ Read from file
▫ Demux
▫ Decode
▫ Encode
▫ Stream to network
• Tasks:
▫ Loads the filters
▫ connect Filters
▫ Change filter states
▫ Disconnect filters
▫ Remove filters from graph.
• The graph is always unidirectional (No loops)
• Have three basic states: Play, Pause, Stop.


DMOs
• DirectX® Media Objects (DMOs)
• Create stream processing object that could
operate without a graph (Filters could only work
as part of a graph)
• DMOs could operate inside a graph using a
“DMO Wrapper” which acts as a filter
• Advantage
▫ Simpler interface
▫ No need to create a graph


DSP-IP Contact information
For Course materials & lecture request contact:
Adi Yakov
Training and Courses Manager
adi@dsp-ip.com
+972-9-8651933
For projects development services contact:
Alona Ashkenazi
Technology Management Services :
alona@dsp-ip.com
+972-9-8850956 www.dsp-ip.com
Mail : info@dsp-ip.com
Phone: +972-9-8850956,
Fax : +972-50- 8962910


1– Introduction To Direct Show

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1– Introduction To Direct Show