Synchronous transmission over packet based network

1. A method of transmission over a packet based network, comprising:

providing a plurality of data packets to be transmitted on the packet based network during a predetermined time interval;

arranging the plurality of provided data packets in a single transmission block, at relative locations within the block, selected according to desired transmission times of the data packets, such that one or more gaps remain between at least some of the data packets;

adding padding bytes to the transmission block in a manner which substantially fills the one or more gaps; and

providing the block for transmission on the packet based network,

wherein arranging the data in the transmission block comprises overwriting one or more padding packets with one or more data packets.

2. A method according to claim 1 , wherein adding padding bytes to the transmission block comprises adding padding bytes to one or more of the data packets.

3. A method according to claim 1 , wherein adding padding bytes to the transmission block comprises adding padding packets.

4. A method according to claim 3 , wherein adding padding packets comprises adding packets having an error which causes them to be discarded by standard routers.

5. A method according to claim 3 , wherein adding padding packets comprises adding packets in which the source address of the packet is the same as the-destination address of the packet or packets having a zero or one time to live value.

6. A method according to claim 3 , wherein each padding packet has a size of at least 40 bytes.

7. A method according to claim 1 , wherein adding padding bytes to the transmission block comprises adding such that the data packets and the padding bytes are together of a size substantially equal to a capacity of the packet based network during the predetermined time interval.

8. A method according to claim 7 , wherein adding the padding bytes comprises adding such that the data packets and the padding bytes are together not smaller by more than 100 bytes from a capacity of the packet based network during the predetermined time interval.

9. A method according to claim 1 , wherein adding the padding bytes comprises adding such that the provided data packets and padding bytes together occupy at least 99% of the capacity of the packet based network during the predetermined time interval.

10. A method of transmission over a packet based network, comprising:

providing a plurality of data packets to be transmitted on the packet based network during a predetermined time interval;

arranging the plurality of provided data packets in a single transmission block, at relative locations within the block, selected according to desired transmission times of the data packets, such that one or more gaps remain between at least some of the data packets;

adding padding bytes to the transmission block in a manner which substantially fills the one or more gaps; and

providing the block for transmission on the packet based network,

wherein the predetermined time interval is longer than 10 milliseconds.

11. A method according to claim 1 , wherein providing the data packets comprises providing real time media packets.

12. A method according to claim 1 , wherein providing the data packets to be transmitted comprises providing from a plurality of video streams having a same data rate.

13. A method according to claim 1 , wherein providing the data packets to be transmitted comprises providing from a plurality of video streams, at least two of which have different data rates.

14. A method of transmission over a packet based network, comprising:

providing a plurality of data packets to be transmitted on the packet based network during a predetermined time interval;

arranging the plurality of provided data packets in a single transmission block, at relative locations within the block, selected according to desired transmission times of the data packets, such that one or more gaps remain between at least some of the data packets;

adding padding bytes to the transmission block in a manner which substantially fills the one or more gaps; and

providing the block for transmission on the packet based network,

wherein arranging the data packets comprises defining a plurality of channels, dividing the block into a plurality of cycles including a packet for each of the channels and placing a padding packet between each of the cycles.

15. A method of transmission over a packet based network, comprising:

providing a plurality of data packets to be transmitted on the packet based network during a predetermined time interval;

arranging the plurality of provided data packets in a single transmission block, at relative locations within the block, selected according to desired transmission times of the data packets, such that one or more gaps remain between at least some of the data packets;

adding padding bytes to the transmission block in a manner which substantially fills the one or more gaps; and

providing the block for transmission on the packet based network,

wherein adding the padding bytes comprises adding after the data packets were arranged in the block.

16. A method of transmission over a packet based network, comprising:

providing a plurality of data packets to be transmitted on the packet based network during a predetermined time interval;

arranging the plurality of provided data packets in a single transmission block, at relative locations within the block, selected according to desired transmission times of the data packets, such that one or more gaps remain between at least some of the data packets;

adding padding bytes to the transmission block in a manner which substantially fills the one or more gaps; and

providing the block for transmission on the packet based network,

wherein adding the padding bytes comprises adding at least one padding packet to the block before the data packets were arranged in the block.

17. A packet based network transmitter, comprising:

a packet based network interface;

a data input unit; and

a processor adapted to arrange data packets received through the data input unit for transmission through the packet based network interface during a predetermined time into a block according to desired transmission times of the packets, with one or more gaps between the data packets, and to add padding bytes to the one or more gaps in a manner which substantially fills the one or more gaps,

wherein the packet based network interface is configured to be periodically initiated to consecutively transmit the packets in the block, with a period of less than 20 times a second.

18. A transmitter according to claim 17 , wherein the block has a size of at least 99% of the capacity of the network interface during the predetermined time.

19. A transmitter according to claim 17 , wherein the network transmitter comprises a VoD server or a physical multiplexer.