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DV/HDV Tape Drive Synchronization. Stereoscopic Displays and Applications Conference 29 th – 31 th January 2007 San Jose, United States. Overview. Introduction to the Stereoscopic Multiplexer Concept and architecture DirectShow capture graphs Simple tape drive synchronization Basic idea

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dv hdv tape drive synchronization

DV/HDV Tape Drive Synchronization

Stereoscopic Displays and Applications Conference

29th – 31th January 2007

San Jose, United States

overview
Overview
  • Introduction to the Stereoscopic Multiplexer
    • Concept and architecture
    • DirectShow capture graphs
  • Simple tape drive synchronization
    • Basic idea
    • Missync detection
  • Advanced tape synchronization concepts
    • Buffering data in system memory
    • Recognizing invalid scenes

Peter Wimmer - 3dtv.at

stereoscopic multiplexer concept
Stereoscopic Multiplexer Concept

R

L

R

L

Right stream

Left stream

Combined video stream

Peter Wimmer - 3dtv.at

directshow
DirectShow
  • DirectShow
    • Architecture to process media data on the Windows platform
    • Processing objects are called filters
    • Filters expose input and output pins
    • Filter pins can be connected to a directed graph
    • Each capture device is represented by a capture filter
  • Stereoscopic Multiplexer
    • Not a proprietary capture applications but …
    • … implemented as DirectShow capture filter
    • Can be used from any capture application

Peter Wimmer - 3dtv.at

directshow capture graph
DirectShow Capture Graph
  • The capture application loads…
    • … the capture device filter
    • … the downstream filters
  • Example downstream filters are
    • … video renderers
    • … file writer
    • … network renderer

Capture

Device

Sink

Peter Wimmer - 3dtv.at

stereoscopic multiplexer capture graph
Stereoscopic Multiplexer Capture Graph

3dtv.at

Stereoscopic

Multiplexer

Sink

Left

Capture

Device

Right

Capture

Device

  • The application loads…
    • … the Stereoscopic Multiplexer
    • … the downstream filters
  • The Stereoscopic Multiplexer loads…
    • … the ‘real’ physical capture drivers
    • … video decoders (if required)

Peter Wimmer - 3dtv.at

stereoscopic multiplexer architecture
Stereoscopic Multiplexer Architecture

Application

Application

DirectShow-

Filter

Stereoscopic Multiplexer

User

Mode

WDM Video

Capture Filter

WDM Video

Capture Filter

WDM Video

Capture Filter

Miniport

Driver

MiniportDriver

Miniport Driver

Kernel

Mode

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stereoscopic video recording
Two camcorders + remote control

Full resolution

Optimum image quality

No immediate playback possible

One camcorder + optical attachment

Half resolution per eye

Degraded image quality

Simple playback

Stereoscopic Video Recording

Peter Wimmer - 3dtv.at

dual tape playback
Dual Tape Playback
  • Problem
    • Different number of frames on the tapes
    • Usually happens when camcorders were turned off
  • Playing back dual camcorder recordings
    • Starting both tapes simultaneously  tapes drift apart
    • Transfer both tapes to harddisk  splitting scenes playing each scene separately  ok but inconvenient

Peter Wimmer - 3dtv.at

tape synchronization
Tape Synchronization
  • Tape synchronization involves…
    • … detecting missync
    • … correcting missync
  • Detecting missync
    • Image analysis: tracking motion and parallax not reliable, computationally complex
    • Sound analysis: detecting corresponding events in the left and right audio track does not work for silent scenes
    • Scene change detection: based on metadata (recording date and time) in the compressed DV stream reliable, no computational overhead

Peter Wimmer - 3dtv.at

basic tape synchronization
Basic Tape Synchronization
  • Resynchronize
    • Pause first tape
    • Wait for scene changeon second tape
    • Pause second tape
    • Step forward tosmallest common offset from the scene changes
    • Send ‘play’ commandto both tapes
  • A tolerance of one frame is good tradeoff between playback interruptionsand sync quality

Wait for

scene change

Yes

Scene change occurs

on the other tape within

a certain tolerance?

No

Resynchronize

Peter Wimmer - 3dtv.at

basic tape synchronization graph
Basic Tape Synchronization Graph

Tape control

Timecode

Recording date/time, timecode

Microsoft

DV Camera

and VCR

3dtv.at

Metadata

Reader

DV Video

Decoder

3dtv.at

Stereoscopic

Multiplexer

Sink

Microsoft

DV Camera

and VCR

3dtv.at

Metadata

Reader

DV Video

Decoder

Created by Stereoscopic Multiplexer

Peter Wimmer - 3dtv.at

tape synchronization graph with audio
Tape Synchronization Graph with Audio
  • Audio data are sent to sound card
  • Audio data are not available for capturing

3dtv.at

Audio Slaving

Filter

Audio

Renderer

Media type: A/V interleaved

Microsoft

DV Camera

and VCR

3dtv.at

Metadata

Reader

DV Splitter

DV Video

Decoder

3dtv.at

Stereoscopic

Multiplexer

Media type: Video only

Microsoft

DV Camera

and VCR

3dtv.at

Metadata

Reader

DV Video

Decoder

Peter Wimmer - 3dtv.at

hdv support
HDV Support
  • HDV standards
    • HDV1: 720p (1280 x 720 pixels), used by JVC
    • HDV2: 1080i (1440 x 1080 pixels), used by Sony and Canon
    • MPEG-2 interframe compression
  • Downconversion mode
    • Standard definition playback  low system requirements
    • Firewire output of camcorders set to DV mode
    • Camcorders perform downconversion from HDV to DV
    • DV graphs still work
  • Native HDV mode
    • High definition playback  high system requirements
    • Metadata readers parse MPEG streams
    • Changes to the filter graph are necessary

Peter Wimmer - 3dtv.at

hdv graph
HDV Graph

MPEG

Audio Decoder

3dtv.at

Audio Slaving

Filter

Audio

Renderer

Audio stream

  • MPEG transport stream
    • PID 0810h: Elementary video stream
    • PID 0814h: Elementary audio stream
    • PID 0811h: Video auxiliary stream (contains metadata)

Microsoft

AVC Tape

Subunit Device

MPEG-2

Demultiplexer

3dtv.at

Metadata

Reader

MPEG-2

Video Decoder

Video stream

Video aux stream

3dtv.at

Stereoscopic

Multiplexer

3dtv.at

Metadata

Reader

MPEG-2

Video Decoder

Microsoft

AVC Tape

Subunit Device

MPEG-2

Demultiplexer

Peter Wimmer - 3dtv.at

advanced tape synchronization
Advanced Tape Synchronization
  • Problems with basic tape synchronization
    • Frequent playback interruptions
    • Frames are multiplexed in the order they arrive
    • Precision only approx. ±1 frame
  • Solution
    • Synchronize the multiplexer output, not the camcorders
    • Buffer data in system memory to delay the stream that is ahead
    • Resynchronize tapes only if buffer is full
    • Precise synchronization based on offset from scene change
  • Invalid scene recognition
    • Detect scenes that are present just on one of the tapes
    • Pause the other tape until matching scenes have been found
    • Implementation: Monitor difference of left and right recording date/time
    • Clock time might not be set accurately  do not monitor absolute time

Peter Wimmer - 3dtv.at

invalid scene recognition
Invalid Scene Recognition
  • Do not drop the first scene after startup
  • Do not drop the first scene after a recording break (it is likely that the clocks have been adjusted or another pair of camcorders was used)

Peter Wimmer - 3dtv.at

advanced tape synchronization graph
Advanced Tape Synchronization Graph
  • Media sample buffers operate on compressed streams
  • Buffering one second DV/HDV video requires 3.5 MB of memory

3dtv.at

Audio Slaving

Filter

Audio

Renderer

Microsoft

DV Camera

and VCR

3dtv.at

Media Sample

Buffer

3dtv.at

Metadata

Reader

DV Splitter

DV Video

Decoder

3dtv.at

Stereoscopic

Multiplexer

DV Video

Decoder

Microsoft

DV Camera

and VCR

3dtv.at

Media Sample

Buffer

3dtv.at

Metadata

Reader

Peter Wimmer - 3dtv.at

stereoscopic multiplexer versions
Version 0.5 (May 2006)

Basic DV tape synchronization

Configuration tool

Version 0.6 (Q1 2007)

Advanced DV/HDV tape synchronization

HDV support (HDV2 only)

Stereoscopic Multiplexer Versions

Peter Wimmer - 3dtv.at

thanks for your attention

Q&A

Thanks for Your Attention

Visit us at http://www.3dtv.at!

Peter Wimmer - 3dtv.at

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