The present invention relates generally to video images. More particularly, an embodiment of the present invention relates to the decoding and display of high dynamic range video.
As used herein, the term ‘dynamic range’ (DR) may relate to a capability of the human psychovisual system (HVS) to perceive a range of intensity (e.g., luminance, luma) in an image, e.g., from darkest darks (blacks) to brightest brights (whites). In this sense, DR relates to a ‘scene-referred’ intensity. DR may also relate to the ability of a display device to adequately or approximately render an intensity range of a particular breadth. In this sense, DR relates to a ‘display-referred’ intensity. Unless a particular sense is explicitly specified to have particular significance at any point in the description herein, it should be inferred that the term may be used in either sense, e.g. interchangeably.
As used herein, the term high dynamic range (HDR) relates to a DR breadth that spans the some 14-15 orders of magnitude of the human visual system (HVS). For example, well adapted humans with essentially normal (e.g., in one or more of a statistical, biometric or ophthalmological sense) have an intensity range that spans about 15 orders of magnitude. Adapted humans may perceive dim light sources of as few as a mere handful of photons. Yet, these same humans may perceive the near painfully brilliant intensity of the noonday sun in desert, sea or snow (or even glance into the sun, however briefly to prevent damage). This span though is available to ‘adapted’ humans, e.g., those whose HVS has a time period in which to reset and adjust.
In contrast, the DR over which a human may simultaneously perceive an extensive breadth in intensity range may be somewhat truncated, in relation to HDR. As used herein, the terms enhanced dynamic range (EDR) or visual dynamic range (VDR) may individually or interchangeably relate to the DR that is perceivable by short-term adaptation though a HVS. As used herein, EDR may relate to a DR that spans 5 to 6 orders of magnitude. Thus while perhaps somewhat narrower in relation to true scene referred HDR, EDR nonetheless represents a wide DR breadth.
In practice, images comprise one or more color components (e.g., luma Y and chroma Cb and Cr) wherein each color component is represented by a precision of n-bits per pixel (e.g., n=8). Using linear luminance coding, images where n≦8 (e.g., color 24-bit JPEG images) are considered images of standard dynamic range, while images where n>8 may be considered images of enhanced dynamic range. EDR and HDR images may also be stored and distributed using low bit-depth, non-linear luminance coding (e.g., 10-bits and logarithmic luminance coding), or high-precision (e.g., 16-bit) floating-point formats, such as the OpenEXR file format developed by Industrial Light and Magic.
Most consumer desktop displays support luminance of 200 to 300 cd/m2 or nits. Most consumer HDTVs range from 300 to 1000 cd/m2. Such conventional displays thus typify a low dynamic range (LDR), also referred to as a standard dynamic range (SDR), in relation to HDR or EDR. As the availability of EDR content grows due to advances in both capture equipment (e.g., cameras) and EDR displays (e.g., the PRM-4200 professional reference monitor from Dolby Laboratories), EDR content may be color graded and displayed on EDR displays that support higher dynamic ranges (e.g., from 1,000 nits to 5,000 nits or more). In general, the methods of the present disclosure relate to any dynamic range higher than SDR.
To support backwards compatibility with legacy playback devices as well as new HDR or ultra-high definition (UHD) display technologies, multiple bitstream layers may be used to deliver UHD and HDR (or EDR) video data from an upstream device to downstream devices. Given such a multi-layer stream, legacy decoders may use one set of layers to reconstruct an HD version of the content with lower dynamic range (LDR) or standard dynamic range (SDR). Advanced decoders may use a second set of layers to reconstruct an HD or UHD EDR version of the content to render it on more capable displays. An example of such system was described in U.S. Provisional Patent Application 61/882,773, to be referred from now on as the '773 Application, filed on Sep. 26, 2013, titled “Backward-compatible coding for ultra-high definition signals with enhanced dynamic range,” (filed also as PCT Application Ser. No. PCT/US2013/073085, on Dec. 4, 2013) which is incorporated herein by reference in its entirety.
Processing in an EDR receiver may be considered to include two major components: a) decoding and blending the two stream layers to generate a decoded EDR video signal, and b) performing display management (e.g., tone and gamut mapping) on the decoded EDR video signal to adapt it for optimum display onto the target EDR display. These image-dependent operations may be assisted or controlled by EDR metadata generated by the source of the EDR content and multiplexed into the coded EDR bitstream.
In some use cases, existing set-top boxes may not have enough processing power to perform image-content dependent display management to yield the best possible video quality performance. As appreciated by the inventors here, improved techniques for the decoding and display of EDR video are desirable.
The approaches described in this section are approaches that could be pursued, but not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated, it should not be assumed that any of the approaches described in this section qualify as prior art merely by virtue of their inclusion in this section. Similarly, issues identified with respect to one or more approaches should not assume to have been recognized in any prior art on the basis of this section, unless otherwise indicated.
An embodiment of the present invention is illustrated by way of example, and not in way by limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements and in which:
Methods and systems for the decoding and display of EDR video signals are described herein. In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, that the present invention may be practiced without these specific details. In other instances, well-known structures and devices are not described in exhaustive detail, in order to avoid unnecessarily occluding, obscuring, or obfuscating the present invention.
Overview
Example embodiments described herein relate to the decoding, and display of images with high or enhanced dynamic range. In an embodiment, a digital media player receives a coded, layered bitstream, of enhanced dynamic range (EDR) to be displayed on an EDR display. To accommodate legacy media players with limited computational resources, some of the decoding operations are moved from the player to it attached EDR display. A video decoder on the digital media player extracts and decodes a base layer, an enhancement layer, and metadata from the coded EDR stream. It then converts the two layers and input graphics into a common video format suitable for embedding the metadata. In an embodiment, 8-bit video and graphics data are converted into a common 12-bit YCbCr 4:2:2 format. The converted signal layers and the graphics are interleaved and the interleaved signal and the embedded metadata are transmitted to an EDR display using a standard interface (e.g., HDMI). On the display, the signal layers and the graphics are de-interleaved. The two signal layers are combined together to generate an EDR signal, which is adapted to be displayed on the display's panel using a display management process guided by the received metadata. The received graphics data are blended with the output of the DM process and the final video output is displayed on the display's panel.
In an embodiment, the interleaved 12-bit YCbCr data are transmitted to the display using an 8-bit, RGB, 4:4:4, HDMI format.
In another embodiment, a video decoder on the digital media player extracts and decodes a base layer, an enhancement layer, and metadata from the coded EDR stream. It then composes a 2D EDR signal which is blended with metadata and alpha blend values. Input graphics and the blended 2D EDR signal are re-formatted as 3D video data and are transmitted to an EDR display using a standard interface for 3D video (e.g., HDMI). On the display, the EDR signal, display metadata, and the graphics are decoded. The EDR signal is adapted to be displayed on the display's panel using a display management process guided by the received metadata. The received graphics data are blended with the output of the DM process and the final video output is displayed on the display's panel.
Delivery of EDR Signals
Existing display and play-back devices, such as HDTVs, set-top boxes, or Blu-ray players, typically support signals of up to 1080p HD resolution (e.g., 1920×1080 pixels at 60 frames per second). For consumer applications, such signals are now typically compressed using a bit-depth of 8 bits per pixel per color component. Because of the 8-bit depth and the corresponding low dynamic range, such signals are typically referred to as signals with standard dynamic range (SDR).
As new television standards are being developed, such as Ultra-High Definition (UHD), it may be desirable to encode signals with enhanced resolution and/or enhanced dynamic range while allowing legacy decoders to still be able to receive and decode a version of the same signal with lower dynamic range (e.g., SDR). An example of such a system is described in U.S. Provisional Patent Application with Ser. No. 61/894,198 (to be referred as the '198 Application), filed on Oct. 22, 2013, titled “Distribution of multi-format high dynamic range video using layered coding,” by G-M Su et al., and incorporated herein by reference in its entirety (filed also on Feb. 14, 2014 as PCT Application Ser. No. PCT/US2014/016544).
Given a layered signal delivery format,
Video decoders (115) and (120) receive the coded bit streams (VES1, VES2) and generate uncompressed video signals (117) and (122). These decoders may comprise different hardware decoders or they may be implemented using a single decoder. In an embodiment, without limitation, video decoder-1 may be an AVC (or H.264) video decoder and video decoder-2 (120) may be an AVC or HEVC video decoder. In other embodiments, video decoders (115, 120) may be based on the MPEG-2, MPEG-4, HEVC, VC-1, VP8, VP9, or any other suitable video compression format. In an embodiment, without limitation, video signals (117) and (122) may be decoded in the YCbCr 4:2:0 format. As used herein, the term ‘video format’ may relate to any information related to the representation of an image or video signal, such as resolution, bit depth, color format representation (e.g., RGB or YCbCr), chroma sub-sampling (e.g., 4:2:0, 4:2:2, or 4:4:4), frame rate, and the like.
Composer (125) receives the decoded BL (117) and EL (122) signals and combines them to generate a decoded EDR stream (152). For example, as discussed in the '198 Application, in an embodiment, the composer (125) may use a predictor (not shown) to predict an EDR signal from the received BL signal (117), which is then added to the EL signal (122) to generate the output EDR signal (152). The composer's operation may be guided by composer metadata (144), parsed through metadata parser (140) from metadata (112) embedded in the received bit stream (102). Such composer metadata may include such parameters as video coding parameters, filtering parameters, and the like. In some embodiments, composer metadata may also be part of VES1 or VES2 streams; hence they could be extracted by the video decoders (115, 120) instead. In an embodiment, EDR signal (152) may be formatted in an HD 12-bit 4:2:2 or 4:4:4 format.
For graphics processing (e.g., menu overlays) and in order to best match the display characteristics of the target display (155), EDR decoding (150) is typically followed by a series of display management and graphics related operations, such as those depicted in
Graphics and video data are blended in blender (130), and display management (DM) metadata maybe embedded into each video frame using a metadata mixer (135). In an embodiment, the blending in mixer (135) may be done so that the output data (137) is compatible to be transmitted to the display (155) using a standard signal interface, such as HDMI. One example of such metadata mixing is described in U.S. Provisional Application 61/815,080, to be referred to as the '080 Application, filed on Apr. 23, 2013, and titled “Transmitting display management metadata over HDMI,” (filed also on Apr. 7, 2014 as PCT Application PCT/US2014/033129) which is incorporated herein by reference in its entirety. Another example of metadata blending is described in U.S. Provisional Application 61/886,026, to be referred to as the '026 Application, filed on Oct. 2, 2013, and titled “Transmitting display management metadata over HDMI,” (filed also on Sep. 30, 2014, as PCT Application PCT/US2014/058260) which is incorporated herein by reference in its entirety. Hence, output signal (137) may comprise blended video (152) and graphics (104) data, and DM metadata (142).
As described in the '026 and '080 Applications, in some embodiments, metadata (142) may be coded in the LSB of the chroma pixel values of a 12-bit YCbCr 4:2:2 signal. In some other embodiments, for digital media players which support only an 8-bit HDMI interface, the video data and the metadata may be mixed to appear as 8-bit RGB 4:4:4 data.
Due to the complexity of the composer (125) and the display management (145) operations, legacy media players may not have enough computational power to support EDR decoding as depicted in
Output signal (237A) now includes graphics (104) and two sets of decoded video signals (117 and 122), hence, compared to receiver (100), receiver (200A) requires a higher transmission rate of data between its digital media player and the TV (300A). To accommodate the new transfer rate requirements, as depicted in
In some embodiment, depending on the color format of the decoded video signals, as depicted in
Display management and composer metadata (242), together with graphics related metadata (107) (e.g., alpha blend values) may be blended together (e.g., using the techniques presented in the '026 and '080 Applications) with the output of the interleaver (220) by metadata mixer (135) to generate the final, HDMI-compliant signal (237A) (e.g., as an 8-bit RGB 4:4:4 stream or a 12-bit YCbCr 4:2:2 stream). To facilitate decoding of this stream by the TV (300A), in addition to the protocols described in the '026 and '080 Applications, the HDMI control stream may include some additional flags, such as:
Support for other input frame rates is also possible. For example, if the input video signal is coded at 48 fps, in an embodiment, the total output frame rate may be set at 120 fps, which allows transmitting graphics (104) at 24 fps. Similarly, if the input video signal is coded at 25 fps, in another embodiment, the total output frame rate may be set at 100 fps, which allows transmitting graphics (104) at 50 fps. If the content is coded in other frame rates, practitioners skilled in the art will appreciate that frame rate conversion techniques as known in the art may be also be applied to both the video receiver (200A) and the TV (300A) so that the total frame rate of output signal (237A) is within the total frame rate allowable by the interface standards between the digital media player and a target display.
Given the simplified video receiver (200A),
Since received video data (AVC1, AVC2) may be in a format not directly supported for display (e.g., 12-bit YCbCr 4:2:2), depending on the capabilities of the TV, format converters (320) may convert the video data back into another format (e.g., 8-bit YCbCr 4:2:0). For example, 12-bit data may be transformed first to 8-bit data by shifting the data to the right to delete the four least significant bits. Then, the chroma components of the YCbCr 4:2:2 signals may be down-sampled to generate a YCbCr 4:2:0 signal. Composer (325) is similar to composer (125) described earlier. It combines base layer (e.g., AVC1) and enhancement layer (e.g., AVC2) signals into an EDR video signal (327), as specified by the composer metadata (321).
Following the composer operation (325), a display management process (330) (e.g., as the one described earlier or as described in the '104 Application) optimizes the appearance of video signal (327) to generate video output (332) that best matches the display characteristics (e.g., gamut and brightness levels) of the TV's panel (350). TV processor (335) may perform additional processing to video signal (332) (e.g., frame rate conversion, spatial scaling, and the like) to generate video output (337). Input graphics (314) are processed as needed by graphics processor (345) to generate processed graphics data (347). For example, graphics processing (345) may include a format conversion to convert graphics data from the input 12-bit YCbCr 4:2:2 format to a format suitable for the target display (e.g., 8-bit YCbCr 4:4:4 or RGB 4:4:4). Using blender (340), video (337) and graphics data (347) are blended together to generate the final output video signal (342) to be displayed on the TV's panel (350).
Composer (225) in system (200B) may also integrate an optional perceptional quantizer (PQ) which operates on the EDR data and convers the output of the composer (e.g., 125) from the traditional gamma domain to a more suitable perceptual-quantization domain. An example of such a PQ quantizer is described in PCT Application Ser. No. PCT/US2012/068212, filed on Dec. 6, 2012, “Device and method of improving the perceptual luminance nonlinearity-based image data exchange across different display capabilities,” by J. S. Miller, et al., which is incorporated herein by reference in its entirety.
Both systems (200A) and (200B) include a metadata multiplexer (135) to multiplex, as described earlier, video data (e.g., 227) with DM metadata (242) and alpha blend data (107) in a format suitable for transmission over a communication interface, such as HDMI. In addition to the metadata multiplexer (135), receiver (200B) includes a 3D Frame Packing processing unit (230). The purpose of the 3D Frame Packing processor (230) is to combine and reformat the 2D EDR video data (228) and the input graphics (104) to appear as “3D data” suitable for transmission over the communication interface (237B).
Incoming signal (237B) is processed by 3D unpacker and HDMI receiver (360) which has two roles: a) to unpack the incoming 3D video into the two “views” and b) to identify whether the incoming signal is a traditional 3D signal with two separate views, or a 2D EDR signal with one video view (e.g. 228), display management metadata (242, 319), graphics view (104, 314), and graphics alpha blend data (107, 317). If the input signal is a 2D EDR signal, then the associated metadata (312) are also extracted and passed to the metadata descrambler (315) as explained earlier.
As described in the '026 and '080 Applications, after video data and the corresponding metadata are blended, then, on the corresponding EDR over HDMI receiver, a simple cyclic redundancy check (CRC) can identify whether the incoming HDMI data includes hidden EDR metadata. In an embodiment, without limitation, 3D unpacker (360) may use the same CRC check on the received 2D data (228) to help identify whether the data is 2D EDR or 3D SDR. If the CRC test does not fail, then the data comprise 2D EDR data (362), which are passed to the display management processor (330). Received metadata and graphics are also passed to the metadata descrambler (315), which generates alpha blend data (317), and the graphics processor (345). Given video data (362), metadata (312), and graphics data (314), the remaining processing in (300B) is similar to the processing of EDR data in EDR TV (300A) as described earlier. Video and graphics signals may be further transformed from one color format to another as needed. If the video receiver (200B) applied a PQ converter to the EDR signal (227), then the inverse PQ operations may be performed as part of the display management processing (330).
Practitioners skilled in the art will appreciate that while example embodiments utilize the HDMI interface, the methods and systems discussed herein are applicable to media receivers and television sets that may communicate with alternative wired or wireless interfaces.
Example Computer System Implementation
Embodiments of the present invention may be implemented with a computer system, systems configured in electronic circuitry and components, an integrated circuit (IC) device such as a microcontroller, a field programmable gate array (FPGA), or another configurable or programmable logic device (PLD), a discrete time or digital signal processor (DSP), an application specific IC (ASIC), and/or apparatus that includes one or more of such systems, devices or components. The computer and/or IC may perform, control, or execute instructions relating to decoding and display of EDR images, such as those described herein. The computer and/or IC may compute any of a variety of parameters or values that relate to decoding and display of EDR images, as described herein. The image and video embodiments may be implemented in hardware, software, firmware and various combinations thereof.
Certain implementations of the invention comprise computer processors which execute software instructions which cause the processors to perform a method of the invention. For example, one or more processors in a display, an encoder, a set top box, a transcoder or the like may implement methods related to decoding and display of EDR images as described above by executing software instructions in a program memory accessible to the processors. The invention may also be provided in the form of a program product. The program product may comprise any medium which carries a set of computer-readable signals comprising instructions which, when executed by a data processor, cause the data processor to execute a method of the invention. Program products according to the invention may be in any of a wide variety of forms. The program product may comprise, for example, physical media such as magnetic data storage media including floppy diskettes, hard disk drives, optical data storage media including CD ROMs, DVDs, electronic data storage media including ROMs, flash RAM, or the like. The computer-readable signals on the program product may optionally be compressed or encrypted.
Where a component (e.g. a software module, processor, assembly, device, circuit, etc.) is referred to above, unless otherwise indicated, reference to that component (including a reference to a “means”) should be interpreted as including as equivalents of that component any component which performs the function of the described component (e.g., that is functionally equivalent), including components which are not structurally equivalent to the disclosed structure which performs the function in the illustrated example embodiments of the invention.
Equivalents, Extensions, Alternatives and Miscellaneous
Example embodiments that relate to the efficient decoding and display of EDR images are thus described. In the foregoing specification, embodiments of the present invention have been described with reference to numerous specific details that may vary from implementation to implementation. Thus, the sole and exclusive indicator of what is the invention, and is intended by the applicants to be the invention, is the set of claims that issue from this application, in the specific form in which such claims issue, including any subsequent correction. Any definitions expressly set forth herein for terms contained in such claims shall govern the meaning of such terms as used in the claims. Hence, no limitation, element, property, feature, advantage or attribute that is not expressly recited in a claim should limit the scope of such claim in any way. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.
This patent application claims the benefit of priority to U.S. Provisional Application Ser. No. 61/911,943, filed on Dec. 4, 2013, “Decoding and Display of High Dynamic Range Video,” and U.S. Provisional Application Ser. No. 61/938,823, filed on Feb. 12, 2014, “Decoding and Display of High Dynamic Range Video,” each of which is incorporated herein by reference in its entirety.
Number | Date | Country | |
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61938823 | Feb 2014 | US | |
61911943 | Dec 2013 | US |