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Hubert Koepfer

Bio: Hubert Koepfer is an academic researcher from Dolby Laboratories. The author has contributed to research in topics: Encoder & Primary color. The author has an hindex of 5, co-authored 6 publications receiving 191 citations.
Topics: Encoder, Primary color, Hue, Code word, Color balance

Papers
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Patent
Guan-Ming Su1, Sheng Qu1, Hubert Koepfer1, Yufei Yuan1, Samir N. Hulyalkar1 
13 Apr 2012
TL;DR: In this paper, multi-channel multiple regression (MMR) models are applied to the efficient coding of images and video signals of high dynamic range, and closed form solutions for the prediction parameters are presented for a variety of MMR models.
Abstract: Inter-color image prediction is based on multi-channel multiple regression (MMR) models. Image prediction is applied to the efficient coding of images and video signals of high dynamic range. MMR models may include first order parameters, second order parameters, and cross-pixel parameters. MMR models using extension parameters incorporating neighbor pixel relations are also presented. Using minimum means-square error criteria, closed form solutions for the prediction parameters are presented for a variety of MMR models.

57 citations

Patent
01 Nov 2012
TL;DR: In this paper, a base layer and one or more enhancement layers may be used to carry video signals, wherein the base layer cannot be decoded and viewed on its own, and the image data in the enhancement layer video signals may comprise residual values, quantization parameters, and mapping parameters based in part on a prediction method corresponding to a specific method used in the advanced quantization.
Abstract: Techniques use multiple lower bit depth codecs to provide higher bit depth, high dynamic range, images from an upstream device to a downstream device. A base layer and one or more enhancement layers may be used to carry video signals, wherein the base layer cannot be decoded and viewed on its own. Lower bit depth input image data to base layer processing may be generated from higher bit depth high dynamic range input image data via advanced quantization to minimize the volume of image data to be carried by enhancement layer video signals. The image data in the enhancement layer video signals may comprise residual values, quantization parameters, and mapping parameters based in part on a prediction method corresponding to a specific method used in the advanced quantization. Adaptive dynamic range adaptation techniques take into consideration special transition effects, such as fade-in and fade-outs, for improved coding performance.

53 citations

Patent
25 Mar 2014
TL;DR: In this article, a set of image blocks of non-zero standard deviations in VDR code words in at least one input VDR image is constructed, and a candidate set of function parameter values for a mapping function is selected from multiple candidate sets.
Abstract: Input VDR images are received. A candidate set of function parameter values for a mapping function is selected from multiple candidate sets. A set of image blocks of non-zero standard deviations in VDR code words in at least one input VDR image is constructed. Mapped code values are generated by applying the mapping function with the candidate set of function parameter values to VDR code words in the set of image blocks in the at least one input VDR image. Based on the mapped code values, a subset of image blocks of standard deviations below a threshold value in mapped code words is determined as a subset of the set of image blocks. Based at least in part on the subset of image blocks, it is determined whether the candidate set of function parameter values is optimal for the mapping function to map the at least one input VDR image.

33 citations

Patent
13 Apr 2012
TL;DR: In this paper, the color grading process uses a slope, offset, and power (SOP) operation, and an example non-linear prediction model is presented, under the assumption that the colour grading process using a slope and offset operation.
Abstract: Inter-color image prediction is based on color grading modeling. Prediction is applied to the efficient coding of images and video signals of high dynamic range. Prediction models may include a color transformation matrix that models hue and saturation color changes and a non-linear function modeling color correction changes. Under the assumption that the color grading process uses a slope, offset, and power (SOP) operations, an example non linear prediction model is presented.

26 citations

Patent
03 Jun 2013
TL;DR: In this paper, the authors proposed a joint BLQ-ELQ adaptation method, which given a plurality of candidate sets of parameters for the BLQ, for each candidate set, computes a joint LQ and ELQ distortion value based on a BLQ distortion function, an ELQ, and at least in part on the number of input pixels to be quantized by the ELQ.
Abstract: An encoder receives one or more input pictures of enhanced dynamic range (EDR) to be encoded in a coded bit stream comprising a base layer and one or more enhancement layer. The encoder comprises a base layer quantizer (BLQ) and an enhancement layer quantizer (ELQ) and selects parameters of the BLQ and the ELQ by a joint BLQ-ELQ adaptation method which given a plurality of candidate sets of parameters for the BLQ, for each candidate set, computes a joint BLQ-ELQ distortion value based on a BLQ distortion function, an ELQ distortion function, and at least in part on the number of input pixels to be quantized by the ELQ. The encoder selects as the output BLQ parameter set the candidate set for which the computed joint BLQ-ELQ distortion value is the smallest. Example ELQ, BLQ, and joint BLQ-ELQ distortion functions are provided.

19 citations


Cited by
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Patent
09 Jul 2015
TL;DR: In this article, the authors proposed a method to enable correct stream reception to take place at the receiving end, in a manner accurately adapted to dynamic changes in delivered content, by using identifying information for identifying the first mode and the second mode is inserted into the video stream.
Abstract: The purpose of the present invention is to enable correct stream reception to take place at the receiving end, in a manner accurately adapted to dynamic changes in delivered content. In a first transmission mode, a predetermined number of extended video streams constituting scalable-coded image data, and respectively including a basic video stream that includes lowest-layer image data, and image data of layers other than the lowest layer. In a second transmission mode, only the basic video stream that includes basic image data is transmitted. Identifying information for identifying the first mode and the second mode is inserted into the video stream. At the receiving end, the transmission mode can be easily ascertained, making it possible for correct stream reception to take place in a manner accurately adapted to changes in the stream composition, that is, dynamic changes in delivered content.

137 citations

Patent
13 Feb 2014
TL;DR: In this article, a display management processor receives an input image with enhanced dynamic range to be displayed on a target display which has a different dynamic range than a reference display, and a non-linear mapping function generates a first tonemapped signal by mapping the intensity of the input signal from the reference dynamic range into the target dynamic range.
Abstract: A display management processor receives an input image with enhanced dynamic range to be displayed on a target display which has a different dynamic range than a reference display. The input image is first transformed into a perceptually-corrected IPT color space. A non-linear mapping function generates a first tone-mapped signal by mapping the intensity of the input signal from the reference dynamic range into the target dynamic range. The intensity (I) component of the first tone-mapped signal is sharpened to preserve details, and the saturation of the color (P and T) components is adjusted to generate a second tone-mapped output image. A color gamut mapping function is applied to the second tone-mapped output image to generate an image suitable for display onto the target display. The display management pipeline may also be adapted to adjust the intensity and color components of the displayed image according to specially defined display modes.

133 citations

Patent
08 Dec 2014
TL;DR: In this paper, a processor and memory containing a client application configures the processor to: request a top level index file identifying a plurality of alternative streams of protected content, where each of the alternative streams are encrypted using common cryptographic information.
Abstract: Systems and methods for performing adaptive bitrate streaming using alternative streams of protected content in accordance with embodiments of the invention are described. One embodiment of the invention includes a processor, and memory containing a client application. In addition, the client application configures the processor to: request a top level index file identifying a plurality of alternative streams of protected content, where each of the alternative streams of protected content are encrypted using common cryptographic information; obtain the common cryptographic information; request portions of content from at least the plurality of alternative streams of protected content; access the protected content using the common cryptographic information; and playback the content.

65 citations

Patent
30 May 2013
TL;DR: In this article, the authors encode multimedia content such as video into multiple adaptive bitrate streams of encoded video and a separate trick play stream of encoded videos to support trick play features.
Abstract: Network services encode multimedia content, such as video, into multiple adaptive bitrate streams of encoded video and a separate trick play stream of encoded video to support trick play features The trick play stream is encoded at a lower encoding bitrate and frame rate than each of the adaptive bitrate streams The adaptive bitrate streams and the trick play stream are stored in the network services During normal content streaming and playback, a client device downloads a selected one of the adaptive bitrate streams from network serviced for playback at the client device To implement a trick play feature, the client device downloads the trick play stream from the network services for trick play playback

61 citations

Patent
01 Nov 2012
TL;DR: In this paper, a base layer and one or more enhancement layers may be used to carry video signals, wherein the base layer cannot be decoded and viewed on its own, and the image data in the enhancement layer video signals may comprise residual values, quantization parameters, and mapping parameters based in part on a prediction method corresponding to a specific method used in the advanced quantization.
Abstract: Techniques use multiple lower bit depth codecs to provide higher bit depth, high dynamic range, images from an upstream device to a downstream device. A base layer and one or more enhancement layers may be used to carry video signals, wherein the base layer cannot be decoded and viewed on its own. Lower bit depth input image data to base layer processing may be generated from higher bit depth high dynamic range input image data via advanced quantization to minimize the volume of image data to be carried by enhancement layer video signals. The image data in the enhancement layer video signals may comprise residual values, quantization parameters, and mapping parameters based in part on a prediction method corresponding to a specific method used in the advanced quantization. Adaptive dynamic range adaptation techniques take into consideration special transition effects, such as fade-in and fade-outs, for improved coding performance.

53 citations