Digital watermarking technique
A watermarking system allowing both sufficiently high quality of watermarked moving pictures and enhanced ease of watermark detection is disclosed. A watermark level of a watermark to be embedded into a picture of data is changed depending on the picture type of a selected block of frequency component data, and then a watermark having the watermark level is inserted into the selected block of frequency component data. Therefore, a moving-picture can be effectively embedded with a digital watermark without substantially reducing the quality of image and the digital watermark can be detected reliably. A relative proportion of watermark levels of I-picture, B-picture, and P-picture is preferably set to 10:7:5.
1. A method for inserting a watermark into a selected block of frequency component data in a picture of data having one of a plurality of picture types selected from the group comprising I-picture, B-picture, and P-picture types, the method comprising the steps of:
determining a picture type of the selected block of frequency component data;
determining a watermark level depending on the picture type of the selected block of frequency component data; and
inserting a watermark selected from a plurality of watermarks stored in a table having the watermark level into the selected block of frequency component data, wherein a total of relative proportion values of watermark levels of I-picture, B-picture, and P-picture types is equal to or smaller than three times a normalized watermark level of an I-picture type.
2. A method for inserting a watermark into a selected block of frequency component data in a picture of data having one of a plurality of picture types selected from the group comprising I-picture, B-picture, and P-picture types, the method comprising the steps of:
storing in a table a plurality of watermarks for each picture type, each of the watermarks corresponding to a different block of the picture of data;
determining a picture type of the selected block of frequency component data;
determining a watermark level depending on the picture type of the selected block of frequency component data;
selecting a watermark from the plurality of watermarks depending on which block is selected; and inserting a selected watermark having the watermark level into the selected block of frequency component data, wherein a total of relative proportion values of watermark levels of I-picture, B-picture, and P-picture types is equal to or smaller than three times a normalized watermark level of an I-picture type.
3. A method for inserting a watermark into a selected block of frequency component data in a picture of data having one of a plurality of picture types selected from the group comprising I-picture, B-picture, and P-picture types, the method comprising the steps of:
a) storing in a table a plurality of watermarks for each of the picture types, wherein a watermark level of the watermarks varies depending on a picture type;
b) selecting a watermark of a type depending on a picture type of the selected block of frequency component data; and
c) inserting a watermark of a selected type into the selected block of frequency component data, wherein a total of relative proportion values of watermark levels of I-picture, B-picture, and P-picture types is equal to or smaller than three times a normalized watermark level of an I-picture type.
4. A system for inserting a watermark into a selected block of frequency component data in a picture of data having one of a plurality of picture types selected from the group comprising I-picture, B-picture, and P-picture types, the system comprising:
a table storing a plurality of watermarks for each of the picture types, wherein a watermark level of the watermarks varies depending on a picture type;
a selector for selecting a watermark of a type depending on a picture type of the selected block of frequency component data; and
an inserting section for inserting a selected watermark of a selected type into the selected block of frequency component data, wherein a total of relative proportion values of watermark levels of I-picture, B-picture, and P-picture types is equal to or smaller than three times a normalized watermark level of an I-picture type.
5. A method for detecting a watermark from a selected block of frequency component data in a picture of data having one of a plurality of picture types selected from the group comprising I-picture, B-picture, and P-picture types, comprising the steps of:
storing a plurality of watermarks for each of the picture types, wherein a watermark level of the watermarks varies depending on a picture type and a total of relative proportion values of watermark levels of I-picture, B-picture, and P-picture types is equal to or smaller than three times a normalized watermark level of an I-picture type;
extracting a watermark from the selected block the picture of data;
selecting a watermark from the stored plurality of watermarks depending on a picture type of the selected block; and
determining whether the selected watermark is embedded in the selected block, based on the extracted watermark and the selected watermark.
6. A digital watermarking method comprising the steps of:
at a watermark inserting section for inserting a watermark into a selected block of frequency component data in a picture of data having one of a plurality of picture types selected from the group comprising I-picture, B-picture, and P-picture types,
storing a plurality of watermarks for each picture type, each of the watermarks corresponding to a different block of the picture of data;
determining a picture type of the selected block of frequency component data;
determining a watermark level depending on the picture type of the selected block of frequency component data;
selecting a watermark from the plurality of watermarks depending on which block is selected; and
inserting a selected watermark having the level into the selected block of frequency component watermark data, wherein a total of relative proportion values of watermark levels of I-picture, B-picture, and P-picture types is equal to or smaller than three times a normalized watermark level of an I-picture type, and
at watermark detecting section for detecting a watermark from a selected block of frequency component data in a picture of data having one of a plurality of picture types,
storing a plurality of watermarks for each of the picture types, wherein a watermark level of the watermarks varies depending on a picture type and a total of relative proportion values of watermark levels of I-picture, B-picture, and P-picture types is equal to or smaller than three times a normalized watermark level of an I-picture type;
extracting a watermark from the selected block in the picture of data;
selecting a watermark from the stored plurality of watermarks depending on a picture type of the selected block; and
determining whether the selected watermark is embedded in the selected block, based on the extracted watermark and the selected watermark.
7. A digital watermarking system comprising:
a watermark inserting device for inserting a into a selected block of frequency component data in of data having one of a plurality of picture types selected from the group comprising I-picture, B-picture, and P-picture types; and
a watermark detecting device for detecting a from a selected block of frequency component data in of data having one of a plurality of picture types, wherein the watermark inserting device comprises:
a first table storing a plurality of watermarks for each of the picture types, wherein a watermark level of the watermarks varies depending on a picture type;
a first selector for selecting a watermark of a type depending on a picture type of the selected block of frequency component data; and
an inserting section for inserting a selected watermark of a selected type into the selected block of frequency component data, wherein a total of relative proportion values of watermark levels of I-picture, B-picture, and P-picture types is equal to or smaller than three times a normalized watermark level of an I-picture type, and
the watermark detecting device comprises:
a second table for storing the plurality of watermarks for each of the picture types, wherein a watermark level of the watermarks varies depending on a picture type and a total of relative proportion values of watermark levels of I-picture, B-picture, and P-picture types is equal to or smaller than three times a normalized watermark level of an I-picture type;
an extractor for extracting a watermark from the selected block in the picture of data;
a second selector for selecting a watermark from the stored plurality of watermarks depending on a picture type of the selected block; and
a determiner for determining whether the selected watermark is embedded in the selected block, based on the extracted watermark and the selected watermark.