Adaptive transfer function for video encoding and decoding

Patent metadata

Field	Value
Publication number	US-11445202-B2
Application number	US-202017073263-A
Country	US
Kind code	B2
Filing date	Oct 16, 2020
Priority date	Feb 25, 2014
Publication date	Sep 13, 2022
Grant date	Sep 13, 2022

Abstract

A video encoding and decoding system that implements an adaptive transfer function method internally within the codec for signal representation. A focus dynamic range representing an effective dynamic range of the human visual system may be dynamically determined for each scene, sequence, frame, or region of input video. The video data may be cropped and quantized into the bit depth of the codec according to a transfer function for encoding within the codec. The transfer function may be the same as the transfer function of the input video data or may be a transfer function internal to the codec. The encoded video data may be decoded and expanded into the dynamic range of display(s). The adaptive transfer function method enables the codec to use fewer bits for the internal representation of the signal while still representing the entire dynamic range of the signal in output.

First claim

What is claimed is:

1. A system, comprising:
a video decoder, configured to:
receive encoded C-bit video data, wherein the encoded C-bit video data represents a range of luminance values extracted from N-bit video data, where N>C, and wherein the range of luminance values represented in the encoded C-bit video data is smaller than full dynamic range for luminance of the N-bit video data;
decode the encoded C-bit video data;
determine a dynamic range of a target device, wherein the dynamic range of the target device is greater than the range of luminance values represented in the encoded C-bit video data; and
expand the decoded C-bit video data to generate D-bit video data covering the full dynamic range of the target device, where D>C and D is distinct from N,
wherein, to expand the decoded C-bit video data, the video decoder maps the range of luminance values extracted from the N-bit video data to the full dynamic range of the target device.

2. The system as recited in claim 1 , wherein the range of luminance values extracted from the N-bit video data represents an effective dynamic range of the human visual system for the N-bit video data.

3. The system as recited in claim 1 , wherein the video decoder is further configured to obtain format metadata for the encoded C-bit video data, wherein the format metadata includes an indication of the range of luminance values extracted from the N-bit video data.

4. The system as recited in claim 3 , wherein the format metadata is embedded in the encoded C-bit video data, and wherein, to obtain the format metadata, the video decoder extracts the format metadata from the decoded C-bit video data.

5. The system as recited in claim 3 , wherein the format metadata further includes an indication of a transfer function used to represent the C-bit video data.

6. The system as recited in claim 3 , wherein the video decoder is configured to perform said obtain and said expand for each of one or more video frames or for each of one or more sequences of two or more video frames.

7. The system as recited in claim 3 , wherein the video decoder is configured to perform said obtain and said expand for two or more regions within each of one or more video frames.

8. The system as recited in claim 1 , wherein, to decode the encoded C-bit video data, the video decoder is configured to:
apply an entropy decoding technique to decompress the encoded C-bit video data; and
perform inverse quantization and inverse transform operations on the decompressed C-bit video data output by the entropy decoding technique to generate the decoded C-bit video data.

9. The system as recited in claim 1 , wherein the video decoder maps the range of luminance values to the full dynamic range of the target device according to a transfer function of the target device.

10. The system as recited in claim 1 , wherein the target device is a high dynamic range (HDR) enabled device.

11. A method, comprising:
performing, by a video decoder:
receiving encoded C-bit video data, wherein the encoded C-bit video data represents a range of luminance values extracted from N-bit video data, where N>C, and wherein the range of luminance values represented in the encoded C-bit video data is smaller than full dynamic range for luminance of the N-bit video data;
decoding the encoded C-bit video data;
determining a dynamic range of a target device, wherein the dynamic range of the target device is greater than the range of luminance values represented in the encoded C-bit video data; and
expanding the decoded C-bit video data to generate D-bit video data covering the full dynamic range of the target device, where D>C and D is distinct from N,
wherein expanding the decoded C-bit video data comprises mapping the range of luminance values extracted from the N-bit video data to the full dynamic range of the target device.

12. The method as recited in claim 11 , wherein the range of luminance values extracted from the N-bit video data represents an effective dynamic range of the human visual system for the N-bit video data.

13. The method as recited in claim 11 , further comprising obtaining format metadata for the encoded C-bit video data, wherein the format metadata includes an indication of the range of luminance values extracted from the N-bit video data and an indication of a transfer function used to represent the C-bit video data in an encoder.

14. The method as recited in claim 13 , wherein the format metadata is embedded in the encoded C-bit video data, and wherein obtaining the format metadata comprises extracting the format metadata from the decoded C-bit video data.

15. The method as recited in claim 13 , further comprising performing said obtaining and said expanding for each of one or more video frames or for each of one or more sequences of two or more video frames.

16. The method as recited in claim 13 , further comprising performing said obtaining and said expanding for two or more regions within each of one or more video frames.

17. The method as recited in claim 11 , wherein decoding the encoded C-bit video data comprises:
applying an entropy decoding technique to decompress the encoded C-bit video data; and
performing inverse quantization and inverse transform operations on the decompressed C-bit video data output by the entropy decoding technique to generate the decoded C-bit video data.

18. The method of claim 11 , wherein mapping the range of luminance values to the full dynamic range of the target device comprises mapping according to a transfer function of the target device.

19. An apparatus, comprising:
a decoder configured to decode encoded C-bit video data generated by an encoder to generate decoded C-bit video data representing a range of luminance values extracted from N-bit video data, where N>C, wherein the range of luminance values represented in the encoded C-bit video data is smaller than full dynamic range for luminance of the N-bit video data; and
an inverse adaptive transfer function component configured to:
determine a dynamic range of a target device, wherein the dynamic range of the target device is greater than the range of luminance values represented in the encoded C-bit video data; and
expand the decoded C-bit video data to generate D-bit video data covering the full dynamic range of the target device, where D>C and D is distinct from N,
wherein, to expand the decoded C-bit video data, the inverse adaptive transfer function component maps the range of luminance values extracted from the N-bit video data to the full dynamic range of the target device.

20. The apparatus as recited in claim 19 , wherein the range of luminance values extracted from the N-bit video data represents an effective dynamic range of the human visual system for the N-bit video data.

21. The apparatus as recited in claim 19 , wherein the decoder is further configured to extract format metadata from the encoded C-bit video data and provide the format metadata to the inverse adaptive transfer function component, wherein the format metadata includes an indication of the range of luminance values extracted from the N-bit video data and an indication of a transfer function used to represent the C-bit video data in the encoder.

22. A system, comprising:
a video decoder, configured to perform operations comprising:
receiving a bit stream that includes (i) encoded video data corresponding to a source video data encoded by an encoder, the encoded video data representing a focu

Assignees

• Apple Inc

Inventors

• Tourapis Alexandros
• Singer David

Classifications

• H04N23/741

  by increasing the dynamic range of the image compared to the dynamic range of the electronic image sensors · CPC title

• G09G2320/0666

  for control of colour parameters, e.g. colour temperature · CPC title

• H04N19/188

  the unit being a video data packet, e.g. a network abstraction layer [NAL] unit · CPC title

• H04N19/182

  the unit being a pixel · CPC title

• H04N19/172

  the region being a picture, frame or field · CPC title