libavfilter
DESCRIPTION
PDF of the presentation held at the VideoLAN Dev Days meeting of 3 September 2011, Paris. Short introduction to libavfilter, current development status and future developments.TRANSCRIPT
ProjectIntroduction
Introduction tolibavfilterarchitecture
Examples
FutureDevelopment
Appendixes
Introduction to Libavfilter
Stefano Sabatinimailto:[email protected]
VideoLAN
Video LAN Dev Days - 03 September 2011
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ProjectIntroduction
Introduction tolibavfilterarchitecture
Examples
FutureDevelopment
Appendixes
Summary
1 Project Introduction
2 Introduction to libavfilter architecture
3 Examples
4 Future Development
5 Appendixes
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ProjectIntroduction
Introduction tolibavfilterarchitecture
Examples
FutureDevelopment
Appendixes
Objectives - Why?
provide a media filtering layer to FFmpeg+clientlibraries/apps, replace VHOOKsimplify the design of ff* tools, enhance flexibilityextend the testing framework with ad-hoc filters/sources
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ProjectIntroduction
Introduction tolibavfilterarchitecture
Examples
FutureDevelopment
Appendixes
Libavfilter dependencies
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ProjectIntroduction
Introduction tolibavfilterarchitecture
Examples
FutureDevelopment
Appendixes
High level features
focus on performance (avoid unnecessary memcpies /unnecessary conversions)support all formats supported by FFmpegimplement a sophisticated negotiation formatmechanism, minimize the number of pixel/sampleformat conversionsinteractive features for processing interactivecommands/eventsallow graphs of filters vs. linear chainsallow media sources/sinksallow transmedia filtering
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ProjectIntroduction
Introduction tolibavfilterarchitecture
Examples
FutureDevelopment
Appendixes
Development status
video filtering integrated into ffmpeg.c in May 2010,included in latest FFmpeg/Libav formal releases(0.7/0.8)API/ABI still considered unstableaudio integration is a work in progress
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Introduction tolibavfilterarchitecture
Examples
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Appendixes
Filter node anatomy
A filter contains one or more input/output padsEach pad is bound to a specific media type, supportsone or more input/output formatsinput and output pads are tied together by a linkfilters can be connected together to form a grapha filtergraph is represented through a simple textualdescription
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ProjectIntroduction
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Examples
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Appendixes
Filtering model
a filter processes buffers, a buffer can contain a videoframe or audio samplesthe properties of each buffer (e.g. frame type,timestamp, file position) can be accessed andmanipulated during the filtering processmixed pull/push model
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ProjectIntroduction
Introduction tolibavfilterarchitecture
Examples
FutureDevelopment
Appendixes
Filters
scale - based on libswscalepad, crop, vflip, hflipfrei0r / frei0r_src wrappermp wrapper (MPlayer filters)more: boxblur, delogo, drawtext, lutyuv, lutrgb, yadif,select, unsharp...currently 60 filters+sources+sinks implemented (check-filters option)
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ProjectIntroduction
Introduction tolibavfilterarchitecture
Examples
FutureDevelopment
Appendixes
Misc examples
Example
color=pink,hflip,nullsink
Example
movie=logo.png [logo]; color=bikeshed [color];[color][logo] overlay [out]
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ProjectIntroduction
Introduction tolibavfilterarchitecture
Examples
FutureDevelopment
Appendixes
Future development - 1
audio filtering integration completion (possibly finishedin a few months), sox+ladspa wrappersmore framework changes - e.g. stricter integration withlibavcodec for allowing direct rendering
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ProjectIntroduction
Introduction tolibavfilterarchitecture
Examples
FutureDevelopment
Appendixes
Future development - 2
transmedia filteringsubtitles filteringtransmedia+subtitle filtering: speech recognition / voicesynthesis / subtitles video rendering
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ProjectIntroduction
Introduction tolibavfilterarchitecture
Examples
FutureDevelopment
Appendixes
How to contribute
bug reports/feature requestspatches are welcome!money/food/postcards/stuff
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ProjectIntroduction
Introduction tolibavfilterarchitecture
Examples
FutureDevelopment
Appendixes
Resources
http://ffmpeg.org/libavfilter.html
libavfilter/*.{h,c}doc/examples/filtering.cffmpeg-devel mailing-list
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ProjectIntroduction
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Examples
FutureDevelopment
Appendixes
Licence of this document
Released with Creative Commons licenseAttribution-NonCommercial-ShareAlike (see: http://creativecommons.org/licenses/by-nc-sa/3.0/)
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