SMPTE RDD 2-2007 SMPTE REGISTERED DISCLOSURE DOCUMENT Use of Logarithmic Non-Linear Transfer Characteristic for Transmission of Linear Signals through Limited-Bit-Depth Image Repre.pdf

1、 The attached document is a Proposed Registered Disclosure Document prepared by the proponent identified below. It has been examined by the appropriate SMPTE Technology Committee and is believed to contain adequate information to satisfy the objectives defined in the Scope, and to be technically con

2、sistent. This document is NOT a Standard, Recommended Practice or Engineering Guideline, and does NOT imply a finding or representation of the Society. Errors in this document should be reported to the proponent identified below, with a copy to engsmpte.org. The technology described in this Register

3、ed Disclosure Document may be the subject of patent rights. The proponent declares that it is willing to license all applicable patents owned or controlled by the Company on a worldwide basis under Reasonable terms and Non-Discriminatory conditions. Attention is drawn to the possibility that some of

4、 the elements of this document may be the subject of patent rights other than those identified above. SMPTE shall not be held responsible for identifying any or all such patent rights. All other inquiries in respect of this document, including inquiries as to intellectual property requirements that

5、may be attached to use of the disclosed technology, should be addressed to the proponent identified below. Proponent contact information: Grass Valley (UK) Ltd. Attention: Dave Bancroft The Duran Centre, Units 1 and utilization of an existing curve already in widespread use in the post-production in

6、dustry so as to maximize availability for interchange purposes. 4 Linear Source Signal The output of the analog-to-digital converter attached to each of the three opto-electronic sensors in the camera is specified as: linear out, 12-bits representing decimal code values 0 through 4095; black level i

7、s represented by code value 64; sensor maximum output level is represented by code value 3840. RDD 2-2007 Page 3 of 4 pages 5 Non-Linear Transfer Curve This is applied to the linear source signal. It is a logarithmic curve equivalent to the industry-standard Cineon curve. If x is the input and y is

8、the output, then if x 37 then y = floor 500*log(0.02714189*x)+0.5 else y = 0 where floor is a function that rounds a real number to the nearest integer value, the direction of rounding being towards zero. NOTE The image structure document SMPTE 274M referenced by this document specifies that certain

9、 codes (000h to 003h, 3FC to 3FFh) are prohibited codes that cannot be transmitted even if they are derived from the conversion formula in 5. 6 Interface The non-linear signal from Clause 5 shall be transmitted over two interfaces complying with SMPTE 292 (two interfaces are required because the bit

10、 rate exceeds the capacity of a single SMPTE 292 interface). The division of codewords between the two 292 interfaces shall be in accordance with SMPTE 372M. 7 Reverse Function A reverse function converts the 10-bit non-linear values transmitted over the interface back to the linear output values of

11、 the 12-bit analog-to-digital converters within the camera. If x is the input and y is the output, then y=floor 10 x/500/ 0.02714189 + 0.5 8 Payload Identification Implementations based on the provisions of this document and executed by the documents proponent use operational context to identify imp

12、licitly the nature of the payload (per the provisions of 3). 9 Alternative Use of Look Up Tables As an alternative to the use of the above functions, conversion between linear and non-linear states may also be obtained by means of forward and reverse lookup tables, respectively. Examples of how the

13、functions may be implemented in a Microsoft Excel spreadsheet are given below. Forward: =IF (Nn 37; ROUND(500*LOG(0.02714189*Nn);0); 0) where Nn is the cell number, ranging from 0 through 1023 , containing the LUT input value. RDD 2-2007 Page 4 of 4 pages Reverse: =IF (ROUND(POWER(10;Nn/500)/0.02714189;0)4095, 4095; ROUND(POWER(10;Nn/500)/0.02714189;0) where Nn is the cell number, ranging from 0 through 4095, containing the LUT input value.