Understudied Constraints Imposed by Watermarking Applications Jeffrey Bloom Dialogic Research (Some work done while at Thomson) With post-presentation comments added in green. Workshop on Multimedia, Mathematics, and Machine Learning II Banff International Research Station for Mathematical Innovation and Discovery Banff, Alberta July 5-10, 2009
Understudied Problems • Watermark embedding in the compressed domain • Watermark detection in the compressed domain
“Compressed Domain Watermarking” Original Compressed Stream Marked Compressed Stream Watermark Embedding Decode Encode Partial Decode Original Compressed Stream Marked Compressed Stream Entropy Decode Watermark Embedding Entropy Encode Original Compressed Stream Marked Compressed Stream Watermark Embedding This slide discusses the evolution of watermarking compressed streams: from full decompression to partial decompression to true compressed domain watermarking; the last of which is the subject of the first part of this presentation. For situations where partial decode is too expesive.
Stream Replacement Watermark Embedding … … Shows the concept of stream replacement watermarking. A chunk of the stream is replaced with different data (in brown). But where does the brown data come from? Need to step back and review some basic frameworks on the next few slides.
Watermarking Frameworks Blind Embedding Informed Embedding It is this last case (informed embedding / informed detection) that represents the application that motivates this work. An informed embedder can analyze the content off-line and generate side information for the embedder and for the detector. Embed Analyze D W Embed W Blind Detection Informed Detection Detect D Where does the D come from? D Analyze Detect
The Analyze part of the embedder can be separated from the Embed part. The analysis can take place in a powerful server where it can examine the pixel data, the compressed domain syntax elements, and the entropy encoded bitstream. 2-stage Embedding Analysis Entropy Decode Full Decode D Analysis E P E Stream Embedding
Example: Blu-ray BD Player Virtual Machine Media Transform Self-Protecting Digital Content SPDC is described by CRI in their white paper http://www.cryptography.com/resources/whitepapers/SelfProtectingContent.pdf Use of this technology in Blu-ray is discussed at http://www.cryptography.com/technology/spdc/index.html among other places.
SPDC • Multiple values for each repair • Enables forensic watermarking during repair Preprocess Damaged Compressed Stream Original Compressed Stream Damaged compressed stream is not valuable to a pirate. Damage is done off-line, repair is done at play time. Repair info must be carefully protected. Repair Info Repair Info Damaged Compressed Stream Repaired Compressed Stream Stream Replacement
Identifying the hard problem • Blu-ray • MPEG2, VC1, H.264/AVC • H.264/AVC • CAVLC - Context-adaptive variable-length coding • CABAC - Context-based adaptive binary arithmetic coding • VLC case has been addressed • CABAC is hard • Arithmetic Code • Context Adaptive Blu-ray supports three compression standards VC1 is not widely used H.264 supports two entropy encoding schemes Both MPEG2 and CAVLC
Will be more widely needed E • This scenario is not limited to Blu-ray • CABAC-encoded H.264 is becoming widely deployed • High volume watermarking systems will not have the luxury of doing an entropy-decode/watermark/entropy-encode cycle CABAC Encoded Bitstream Stream Replacement CABAC Encoded Bitstream For adoption of watermarking in high volume network applications, this is an important and understudied problem
Mobile Video Handoff Points Content Delivery Network Mobile Network Operator Local Access Network Content Owner Content Provider Content Delivery Network Backbone Network • eg., back to Internap • eg., AT&T • eg., Rogers Wireless • eg., MTV • eg., Hulu • eg., Akamai, Internap • eg., Global Crossing What happens when I want to watch The Daily Show on my mobile phone from here in Banff? Many different people “touch” the content. This slide shows an example of the how the video gets to my phone. Each participant will optimize the content for its own network. This often involves transcoding. Watermarks can be used to help track content. Detectors distributed throughout multiple networks.
Watermarking Challenge • Tracking watermark embedded by content owner • Embedding can be done in any convenient domain • Watermark detection at various points in the network for tracking • Watermark must be recoverable from any compressed domain without decoding • MPEG2 • H.263 • MPEG4 • H.264/AVC
Watermarking Challenge • Assume that we can do entropy decode pixels pixels Transcoder Transcoder Encode Decode Encode Decode Encode At any point, the stream can be decoded and the watermark recovered from the pixels Conceptually, we can consider a transcoder as a decode/encode pair with pixels in the middle. pixels Decode Detect • Intermediate transcodes look like noise model as a single transcode plus noise • Information is in there Note the colors indicate matching encode/decode pairs (same coding standard). Consider pixels before the red encode and the pixels after the red decode. The pixels after are the same as the pixels before plus coding noise from the red encode.
Watermarking Challenge • Assume that we can do entropy decode pixels pixels Transcoder Transcoder Encode Decode Encode Decode Encode pixels Decode Detect • Intermediate transcodes look like noise model as a single transcode plus noise • Information is in there
Watermarking Challenge • Assume that we can do entropy decode pixels Encode Decode Encode pixels Decode Detect • Intermediate transcodes look like noise model as a single transcode plus noise • Information is in there
Watermarking Challenge • Assume that we can do entropy decode pixels pixels + noise Transcoder Encode Decode Encode pixels Decode Detect • Intermediate transcodes look like noise model as a single transcode plus noise • Information is in there
Summary • Watermark embedding in the entropy-coded compressed domain • Watermark detection in the compressed domain after uncontrolled transcoding For adoption of watermarking in high volume network applications, this is an important and understudied problem For adoption of watermarking for tracking in network applications, this is an important and understudied problem