Method of splicing MPEG encoded video

• US 5,534,944 A
• Filed: 07/21/1995
• Issued: 07/09/1996
• Est. Priority Date: 07/15/1994
• Status: Expired due to Term

• Current Assignee: Panasonic Corporation Of North America (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Corporation Of America (Panasonic Holdings Corporation)
• Inventors: Meyer, Edwin R., Egawa, Ren
• Primary Examiner(s): Metjahic, Safet
• Assistant Examiner(s): West, Nina M.
• Application Number:
  US08/505,581
• Time in Patent Office: 354 Days
• Field of Search: 348/469, 348/467, 348/461, 348/485, 348/584, 348/426, 348/432, 348/473, 348/588, 348/598, 348/599, 348/722, 348/419, 370/118, 370/82, 370/17, 370/94.1
• US Class Current: 348/584
• CPC Class Codes: G06T 9/007 Transform coding, e.g. discrete cosine transform
• CPC Class Codes: G11B 27/036 Insert-editing
• CPC Class Codes: H04N 19/132 Sampling, masking or truncation of coding units, e.g. adaptive resampling, frame skipping, frame interpolation or high-frequency transform coefficient masking
• CPC Class Codes: H04N 19/142 Detection of scene cut or scene change
• CPC Class Codes: H04N 19/146 Data rate or code amount at the encoder output
• CPC Class Codes: H04N 19/152 by measuring the fullness of the transmission buffer
• CPC Class Codes: H04N 19/162 User input
• CPC Class Codes: H04N 19/172 the region being a picture, frame or field
• CPC Class Codes: H04N 19/186 the unit being a colour or a chrominance component
• CPC Class Codes: H04N 19/50 using predictive coding H04N19/61 takes precedence
• CPC Class Codes: H04N 19/61 in combination with predictive coding
• CPC Class Codes: H04N 21/23406 involving management of server-side video buffer
• CPC Class Codes: H04N 21/23424 involving splicing one content stream with another content stream, e.g. for inserting or substituting an advertisement
• CPC Class Codes: H04N 21/23611 Insertion of stuffing data into a multiplex stream, e.g. to obtain a constant bitrate synchronisation arrangements in time-division multiplex systems using bit stuffing for systems with different or fluctuating information rates H04J3/073

Abstract

A method of splicing two compressed video signals which have been encoded according to the standard adopted by the Moving Picture Experts Group (MPEG) determines an amount of null information that is to be inserted between the two video signals in order to ensure that an input buffer of an MPEG decoder does not overflow after receiving the spliced video signals. The method allows a splice to occur after any access unit (picture) in the first compressed video signal. The amount of null information is determined from the data rates of the first and second compressed video signals and the amount of new data which is provided to the buffer before the data is retrieved from the buffer for both the first and second video signals. The video signals are spliced by inserting the null information, as sequence stuffing bits into a buffer immediately after the selected picture in the first video signal. The second video signal is transmitted to the buffer immediately after these stuffing bits.

Claims

1. A method of splicing first and second data streams representing respective first and second encoded signals at a selected boundary in the first data stream using a buffer, wherein each of the first and second data streams has a plurality of decoding time stamps representing times at which data is retrieved from the buffer, the method comprising the steps of:

analyzing the first and second data streams to determine an amount of null information to be inserted in the first data stream after the selected boundary, wherein The amount of null data is determined from the decoding time stamps in the first and second data streams;

transmitting the first data stream, up to the selected boundary to the buffer;

transmitting the determined amount of null information to the buffer;

transmitting the second data stream to the buffer; and

retrieving the spliced data stream from the buffer.

2. A method according to claim 1, wherein the step of transmitting the second data stream to the buffer includes the steps of:

transmitting a first portion of the second data stream to the buffer at the data rate of the first data stream; and

transmitting a second portion of the second data stream to the buffer at the data rate of the second data stream.

3. A method according to claim 2, wherein the data streams are bit-streams encoded according to a standard developed by the motion-picture experts group (MPEG) and the amount of null information is a number of stuffing bits to be inserted before a sequence start code of the second data stream.

4. A method according to claim 3, wherein the amount of null information is determined by the equation:

space="preserve" listing-type="equation">NSTUFF=N.sub.last +N.sub.next +N.sub.splc -N.sub.new

where N_last represents a number of bits in the first data stream between the time that data following the selected boundary is stored into the buffer and the decoder time stamp at which the data following the selected boundary is retrieved from the memory;

N_next represents a number of bits of the first data stream that would be provided in an interval between two decoder time stamps;

N_splc represents a number of bits of the first bit-stream that would be provided in an integer number of intervals between decoder time stamps of the first data stream, the number of bits being greater than or equal to N_new, the number of bits in the second data stream occurring before the first decoder time stamp of the second data stream.

5. A method according to claim 1 wherein the first and second data streams are constant bit-rate data streams and the step of analyzing the first and second data streams to determine the amount of null data is responsive to the respective bit-rates of the first and second data streams.

6. A method according to claim 1 wherein the first data stream is a constant bit-rate data stream and the second data stream is a variable bit-rate data stream having a maximum bit-rate and the step of analyzing the first and second data streams to determine the amount of null data is responsive to the bit-rate of the first data stream and to the maximum bit-rate of the second data stream.

7. A method according to claim 1 wherein the first data stream is a variable bit-rate data stream having a maximum bit-rate and the second data stream is a constant bit-rate data stream and the step of analyzing the first and second data streams to determine the amount of null data is responsive to the maximum bit-rate of the first data stream and to the bit-rate of the second data stream.

8. A method according to claim 1 wherein the first and second data streams are variable bit-rate data streams, each having a respective maximum bit-rate, and the step of analyzing the first and second data streams to determine the amount of null data is responsive to the respective maximum bit-rates of the first and second data streams.

9. A method according to claim 1 further including the steps of:

analyzing the first data stream to determine if the first data stream includes a sequence end code immediately before the selected boundary; and

transmitting the sequence end code to the buffer after the first data stream is transmitted to the buffer when the first data stream does not include a sequence end code immediately before the selected boundary.

10. A method according to claim 1 further including the steps of:

analyzing the second data stream to determine if the second data stream begins with a sequence start code; and

transmitting the sequence start code to the buffer before the second stream is transmitted to the buffer when the second data stream does not begin with a sequence start code.

11. A method of splicing first and second data streams representing respective first and second encoded video signals at a selected boundary in the first data stream using a buffer, wherein each of the first and second video signals has a frame rate and wherein the second data stream has at least one a decoding time stamp representing a time at which data is retrieved from the buffer, the method comprising the steps of:

analyzing the first and second data streams to determine an amount of null information to be inserted in the first data stream after the selected boundary, wherein The amount of null data is determined from the frame rates of the first and second video signals and the decoding time stamp of the and second data stream;

transmitting the first data stream, up to the selected boundary to the buffer;

transmitting the determined amount of null information to the buffer;

transmitting the second data stream to the buffer; and

retrieving the spliced data stream from the buffer.

12. A method according to claim 11, wherein the amount of null information is determined by the equation:

space="preserve" listing-type="equation">NSTUFF=N.sub.last +K*N.sub.next -N.sub.new

where N_last represents a number of bits in the first data stream between the time that data following the selected boundary is stored into the buffer during a frame interval of the first video signal;

Nnext represents a number of bits of the second data stream that would be provided in one frame interval of the second video signal;

Nnew represents the number of bits in the second data stream occurring before the decoder time stamp of the second data stream and the value of K is determined by the inequality K*N_next ≧

N_new -N_last.

13. Apparatus for splicing first and second data streams representing respective first and second encoded signals at a selected boundary in the first data stream using a buffer, wherein each of the first and second data streams has a plurality of decoding time stamps representing times at which data is retrieved from the buffer, the method comprising the steps of:

means for analyzing the first data stream to determine an amount of null information to be inserted in the first data stream after the selected boundary, wherein The amount of null data is determined from the decoding time stamps in the first and second data streams;

means for transmitting the first data stream, up to the selected boundary to the buffer;

means for transmitting the determined amount of null information to the buffer;

means for transmitting the second data stream to the buffer; and

means for retrieving the spliced data stream from the buffer.

14. Apparatus according to claim 13, wherein the first data stream has a constant data rate and the means for transmitting the second data stream to the buffer includes:

means for transmitting a first portion of the second data stream to the buffer at the data rate of the first data stream; and

means for transmitting a second portion of the second data stream to the buffer at a data rate determined from the second data stream.

15. Apparatus according to claim 13 further comprising:

means for analyzing the first data stream to determine if the first data stream includes a sequence end code immediately before the selected boundary; and

means for transmitting the sequence end code to the buffer after the first data stream is transmitted to the buffer when the first data stream does not include a sequence end code before the selected boundary.

16. Apparatus according to claim 13 further comprising:

means for analyzing the second data stream to determine if the second data stream begins with a sequence start code; and

means for transmitting the sequence start code to the buffer before the second stream is transmitted to the buffer when the second data stream does not begin with a sequence start code.