Method for display time stamping and synchronization of multiple video object planes

Abstract

A method of encoding a local time base embedded in the compressed data is disclosed. The local time base is encoded in two parts. The first part has a modulo time base that indicates the specific interval in the reference time base and the second part has a time base increment relative to the reference time. Two forms of time base increment is used to allow for the possibility of different encoding order and displaying order. A mechanism for the synchronization of multiple compressed streams with local time base is also described. A time base offset mechanism is also used to allow finer granularity synchronization of the multiple compressed streams.

1. A method of encoding a local time base of an audio visual sequence in the compressed data comprising the steps of:
 obtaining instances of the audio visual sequence by temporal sampling;    determining the local time base of the said instances to be encoded into compressed data;    encoding the said local time base in two parts, comprising of a modulo time base that marks the occurrence of a set of time reference spaced evenly at a specific interval on the local time base and a time base increment relative to the said evenly spaced time reference;    inserting the modulo time base into the compressed data whenever the specific interval have elapsed; and    inserting the time base increment within the compressed data of the said instances of the audio visual sequence.    
     
     
       2. A method of  claim 1 , wherein a plurality of compressed bitstreams containing local time base information encoded therein are multiplexed and de-multiplexed, for de-multiplexing further comprising the steps of:
 decoding the time base offset of the individual compressed bitstream;    examining the multiplexed bitstream for the next compressed instance and placing the said instance into the appropriate compressed bitstream until a modulo time base is encountered in the multiplexed bitstream;    inserting a modulo time base to each of the compressed bitstreams; and    repeating the last two steps until the multiplexed bitstream is exhausted.    
     
     
       3. A method of decoding a local time base of an audio visual sequence from the time base of the compressed data encoded according to  claim 1  comprising the steps of:
 initializing the reference time base taking into account the time base offset;    incrementing the reference time base by a specific interval for each modulo time base decoded;    decoding the time base increment of the compressed instance; and    determining the decoding time base of the said instance by adding the said decoded time base increment value to the reference time base.    
     
     
       4. A method of encoding the time base according to  claim 1  wherein the local time base, time base increment and time base offsets are in units of milliseconds and the specific interval has a duration of 1000 milliseconds. 
     
     
       5. A method of  claim 1 , wherein a plurality of compressed bitstreams containing local time base information encoded therein are multiplexed, for multiplexing further comprising the steps of:
 synchronizing the local time base of the individual compressed bitstream to a common time base by encoding and inserting the time base offset in the multiplexed bitstream;    examining each of the compressed bitstream for the next compressed instance to be placed into the multiplexed bitstream until all the compressed bitstreams have arrived at the modulo time base;    inserting a common modulo time base into the multiplex bitstream and skipping the modulo time base of the compressed bitstreams; and    repeating the last two steps until all compressed bitstreams are exhausted.    
     
     
       6. A method of multiplexing a plurality of compressed bitstreams as in  claim 5  where the individual compressed bitstreams are themselves multiplexed bitstreams. 
     
     
       7. A method of encoding a local time base of an audio visual sequence in the compressed data comprising the steps of:
 obtaining instances of the audio visual sequence by temporal sampling;    determining the local time base of the said instances to be encoded into compressed data;    encoding the said instances in one of two methods comprising of a first method of compression without reference to any future instances and a second method of compression which refers to the future reconstructed instance;    encoding the said local time base in two parts, comprising of a modulo time base that marks the occurrence of a set of time reference spaced evenly at a specific interval on the local time base and a time base increment;    encoding the time base increment for the instance compressed using the first compression method as an absolute value relative to the said evenly spaced time reference;    encoding the time base increment for the instance compressed using the second compression method as a relative value to the local time base of the previously compressed instance using the said first method;    inserting the modulo time base into the compressed data whenever the specific interval have elapsed; and    inserting the time base increment within the compressed data of the said instances of the audio visual sequence.    
     
     
       8. A method of decoding a local time base of an audio visual sequence from the time base of the compressed data encoded according to  claim 7  comprising the steps of
 initializing the reference time base taking into account of the time base offset;    incrementing the reference time base by a specific interval for each modulo time base decoded;    decoding the time base increment of the compressed instance; and    determining the time base increment to be one of two types, absolute or relative, depending on the first or second compression method used in the encoding of the instance, respectively;    determining the decoding time base of the said instance by adding the said decoded time base increment value to the reference time base if the time base is of the first type; and    determining the decoding time base of the said instance by adding the said decoded time base increment value to the decoding time base of the previous instance encoded using the first compression method, if the time base increment is of the second type.    
     
     
       9. A method for encoding a local time base of a video object plane ( VOP )  comprising:      encoding a time code that indicates a modulo part of a first video object plane  ( VOP )  in a group of video object planes  ( VOPs );      encoding the local time base for the first video object plane  ( VOP )  in a first part and a second part, the first part being a modulo time base indicating a time in one second resolution units that has elapsed since the time code, the second part being a time base increment representing a time increment from a reference time marked by the modulo time base of the first video object plane  ( VOP );      encoding the local time base for each next video object planes  ( VOPs )  following the first video object plane  ( VOP )  in a first part and a second part, the first part being a modulo time base indicating a time in one second resolution units that has elapsed since a reference time marked by the modulo time base of a previous video object plane  ( VOP )  positioned before the next video object plane  ( VOP ) , the second part being a time base increment representing a time increment from a reference time marked by the modulo time base of the next video object plane  ( VOP );      inserting the encoded time code into a group of pictures  ( GOP )  header at the beginning of the group of video object planes  ( VOPs ) ; and        inserting the encoded local time base of the video object plane  ( VOP )  into a bitstream of the video object plane  ( VOP ).