Granted Patent B2

US 8,139,646 · App. 11/718,139 · Granted Mar 20, 2012

Abstract

Claims (27)

1. A method of assembling a first data stream with a second data stream, each data stream comprising coded frames, each coded frame being associated with a relative time value having an integer part determining a period of time to which the coded frame belongs and a part determining the position of the coded frame within said period of time, specific coded frames of a data stream being preceded by an absolute time value, said method comprising the steps of:

calculating a current reference time value for a current coded frame on the basis of a previous reference time value and on an integer part of the current relative time value;

calculating an offset time value on the basis of the reference time value of the last frame in the display order of the first data stream, wherein

the offset time value is equal to the reference time value of the last coded frame in the display order of the first data stream if the part determining the position of the last coded frame in the display order of the first data stream within the period of time is smaller than the part determining the position of the first coded frame in the display order of the second data stream within the period of time, and

the offset time value is equal to the reference time value of the last coded frame in the display order of the first data stream plus one if the part determining the position of the last coded frame in the display order of the first data stream within the period of time is greater than or equal to the part determining the position of the first coded frame in the display order of the second data stream within the period of time; and

modifying the absolute time values of the specific coded frames of the second data stream by adding the offset time value to said absolute time values of said second data stream.

2. A method as claimed in claim 1 , further comprising the steps of:

calculating a modified relative time value for the first frame in the display order of the second data stream from an initial relative time value of said first frame so that said first frame is shifted in the middle of a temporal gap between the last frame of the first data stream and said first frame,

adding a non-coded frame having a null data content in the second data stream, said non-coded frame being associated with the initial relative time value.

3. A method as claimed in claim 1 , further comprising the steps of:

decoding a first set of coded frames at the end of the first data stream and a second set of coded frames at the beginning of the second data stream,

modifying decoded frames of the first set and the second set in such a way that a smooth transition is ensured between the first set and the second set,

coding the modified decoded frames and coding their associated relative time values.

4. A method as claimed in claim 3 , further comprising the step of creating at least one additional frame between the first set and second set of decoded frames.

5. A method as claimed in claim 3 , in which the last decoded frame of the second set is not modified.

6. A non-transitory computer medium comprising program instructions for implementing, when said program is executed by a processor, a method as claimed in claim 1 .

7. The method of claim 1 , wherein the current reference time value for a current coded frame is the sum of the previous reference time value and the integer part of the current relative time value.

8. The method of claim 1 , wherein the relative time value is coded using a variable length code.

9. The method of claim 1 , wherein the period of time is a second.

10. The method of claim 1 , wherein the data stream is an MPEG4 video stream.

11. A device for assembling a first data stream with a second data stream, each data stream comprising coded frames, each coded frame being associated with a relative time value having an integer part determining a period of time to which the coded frame belongs and a part determining the position of the coded frame within said period of time, specific coded frames of a data stream being preceded by an absolute time value, said device comprising:

means for calculating a reference time value for a current coded frame on the basis of a previous reference time value and on an integer part of the current relative time value,

means for calculating an offset time value on the basis of the reference time value of the last frame in the display order of the first data stream, wherein

the offset time value is equal to the reference time value of the last coded frame in the display order of the first data stream if the part determining the position of the last coded frame in the display order of the first data stream within the period of time is smaller than the part determining the position of the first coded frame in the display order of the second data stream within the period of time, and

the offset time value is equal to the reference time value of the last coded frame in the display order of the first data stream plus one if the part determining the position of the last coded frame in the display order of the first data stream within the period of time is greater than or equal to the part determining the position of the first coded frame in the display order of the second data stream within the period of time; and

means for modifying the absolute time values of the specific coded frames of the second data stream by adding the offset time value to said absolute time values of said second data stream.

12. A mobile apparatus comprising a device as claimed in claim 11 .

Assignments (12)