Apparatus for synchronization of digital multimedia data communicated over wired media

• US 20060256822A1
• Filed: 06/30/2005
• Published: 11/16/2006
• Est. Priority Date: 05/12/2005
• Status: Active Grant

• Current Assignee: Radioshack Online IPCO LLC
• Original Assignee: RadioShack Legacy Corporation
• Inventors: Lam, Man Lung Alan, Maung, Tun Oo George, Kwong, Sze Ming Patrick
• Granted Patent: US 7,653,091 B2
• Time in Patent Office: Days
• US Class Current: 370/503
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/22 Traffic shaping
• CPC Class Codes: H04L 47/30 in combination with information about buffer occupancy at either end or at transit nodes
• CPC Class Codes: H04L 47/32 by discarding or delaying data units, e.g. packets or frames
• CPC Class Codes: H04L 47/50 Queue scheduling
• CPC Class Codes: H04L 65/1101 Session protocols
• CPC Class Codes: H04L 65/611 for multicast or broadcast systems for broadcast or conference H04L12/18; arrangements for broadcast or distribution combined with broadcast H04H20/00; arrangements for broadcast applications with a direct linkage to broadcast information or to broadcast space-time H04H60/00; selective distribution of broadcast services, e.g. multimedia broadcast multicast service [MBMS], H04W4/06
• CPC Class Codes: H04L 65/762 at the source reformatting of additional data in video distribution servers H04N21/2355
• CPC Class Codes: H04L 65/764 at the destination reformatting of additional data in video clients H04N21/4355
• CPC Class Codes: H04L 65/80 Responding to QoS

Abstract

An apparatus for synchronizing the initiation of the playback of packetized multimedia data received asynchronously in each receiver in a system, and for synchronizing the real time playback in a plurality of receivers in the system, from the transmitter over a wired communications medium. The clocks in the transmitter encoder and the receiver decoders operate asynchronously but at substantially the same rate. Initiation of playback is synchronized according to the arrival time of a first received data packet having a zero-valued retransmit number. Real time playback among a plurality of receivers is synchronized according to a measured time difference between an operating rate of the encoder and an operating rate of the decoder.

Claims

1-28. -28. (canceled)

29. Apparatus for communicating multimedia data over a wired communication channel, comprising:

a transmitter, operating at a predetermined clock rate, coupled via an interface to the wired communication channel, and further having an encoder for forming data packets having at least a packet sequence number and a packet transmit number associated with the data packet; and

a receiver, coupled via an interface to the wired communication channel and having a timer and a decoder, wherein the decoder operates at a clock rate that is substantially the same as the clock rate of the encoder in the transmitter but independent therefrom; and

means for receiving user entered signals to cause a channel selection signal to be transmitted from the receiver to the transmitter via the wired communication channel.

30. The apparatus of claim 29, further comprising:

means for acknowledging, at each receiver, receipt of a valid received data packet and a correct packet sequence number associated therewith; and

means for synchronizing the initiation of playback of the multimedia data in each receiver according to the arrival time of a first received data packet having a zero-valued transmit number.

31. The apparatus of claim 29, wherein the clock rate of the decoder in the receiver is substantially the same as the clock rate of the encoder in the transmitter within +/−

100 parts per million (ppm).

32. The apparatus of claim 29, wherein the receiver further comprises:

a reserve buffer configured for containing a first threshold number M of received data packets.

33. The apparatus of claim 32, wherein the first threshold number M is two (2) packets.

34. The apparatus of claim 29, wherein the receiver further comprises:

a power line interface;

a transceiver and controller section having a network transceiver and a microcontroller coupled between the power line interface and a decoder; and

at least one decoder and two channel digital-to-analog (DAC) coupled in series from an output of the microcontroller for providing a baseband multimedia output signal.

35. The apparatus of claim 32, wherein the means for synchronizing comprises:

interrupt means responsive to entry of a packet into the reserve buffer in the receiver for initiating decoding of packets to be extracted from the reserve buffer when the reserve buffer is full; and

extraction means for obtaining a data packet from the reserve buffer responsive to initiation of decoding.

36. The apparatus of claim 29, wherein the means for receiving comprises:

an infra red remote control receiver for receiving infra red signals from a user-operable, infra red remote control transmitter.

37. The apparatus of claim 29, wherein the means for receiving comprises:

an infra red remote control receiver for receiving signals from a user-operable keypad disposed on the receiver.

38. The apparatus of claim 29, further comprising:

means for acknowledging, at each receiver, receipt of a valid received data packet and a correct packet sequence number associated therewith; and

means for synchronizing the rate of playback of the multimedia data in each receiver according to a measured time difference between an operating rate of the encoder and an operating rate of the decoder.

39. The apparatus of claim 38, wherein the clock rate of the decoder in the receiver is substantially the same as the clock rate of the encoder in the transmitter within +/−

100 parts per million (ppm).

40. The apparatus of claim 38, wherein the receiver further comprises:

a reserve buffer in the receiver configured for containing a first threshold number M of received data packets.

41. The apparatus of claim 40, wherein the first threshold number M is two (2) packets.

42. The apparatus of claim 38, wherein the receiver further comprises:

a power line interface;

a transceiver and controller section having a network transceiver and a microcontroller coupled between the power line interface and a decoder; and

at least one decoder and two channel digital-to-analog controller (DAC) coupled in series from an output of the microcontroller for providing a baseband multimedia output signal.

43. The apparatus of claim 38, wherein the means for synchronizing comprises:

first interrupt means responsive to arrival of a packet in the receiver for initiating a count up timer if playback has not already started;

second interrupt means responsive to entry of a packet into the reserve buffer in the receiver for initiating decoding of packets extracted from the reserve buffer when the reserve buffer is full; and

comparison means for determining whether accumulated time in the timer, at the instant extraction for decoding begins, exceeds a predetermined second threshold value N.

44. The apparatus of claim 43, wherein the predetermined second threshold N is approximately 500 microseconds.

45. The apparatus of claim 43, wherein the comparison means further comprises:

means for issuing a command to skip the decoding of a sample if the accumulated value in the timer exceeds the predetermined threshold or issuing a command to repeat the decoding of a sample if the value in the timer is less than or equal to the predetermined threshold.