Video Frame Synchronization

Abstract

Embodiments of the invention are generally directed to video frame synchronization. An embodiment of a method includes receiving a first video data stream from a first source at a first port of a multi-port device, a first video frame of the first video data stream arriving at the first port at a first arrival time, and receiving a second video data stream from a second source at a second port of the multi-port device, a second video frame of the second video data stream arriving at the second port at a second arrival time. The method further includes determining an offset between the first arrival time and the second arrival time, determining one or more correction factors based at least in part on the offset, the one or more correction factors including a first correction factor for the first source, and sending a first command to the first source to modify a time of transmission by the first source of a third video frame following the first frame using the correction factor.

What is claimed is: 
     
         1 . A method comprising:
 receiving a first video data stream from a first source at a first port of a multi-port device, a first video frame of the first video data stream arriving at the first port at a first arrival time;   receiving a second video data stream from a second source at a second port of the multi-port device, a second video frame of the second video data stream arriving at the second port at a second arrival time;   determining an offset between the first arrival time and the second arrival time;   determining one or more correction factors based at least in part on the offset, the one or more correction factors including a first correction factor for the first source; and   sending a first command to the first source to modify a time of transmission by the first source of a third video frame following the first video frame using the correction factor.   
     
     
         2 . The method of  claim 1 , wherein the video data is one or more of HDMI™ (High-Definition Multimedia Interface) compatible data and MHL™ (Mobile High-Definition Link) compatible data. 
     
     
         3 . The method of  claim 1 , wherein the command is sent via a command bus between the multi-port device and the first source. 
     
     
         4 . The method of  claim 1 , wherein the first command adjusts alignment of arrival of the third video frame with arrival of a fourth video frame following the second video frame transmitted by the second source. 
     
     
         5 . The method of  claim 4 , wherein the first command provides for synchronizing the arrival of the third video frame at the first port and the arrival of the fourth video frame at the second port at a common time. 
     
     
         6 . The method of  claim 4 , wherein the first command provides for synchronizing the arrival of the third video frame at the first port and the arrival of the fourth video frame at the second port with a certain offset. 
     
     
         7 . The method of  claim 1 , wherein the third video frame arrives at the first port at a third arrival time and the fourth video frame arrives at the second port at a fourth time, further comprising determining a second offset between the third arrival time and the fourth arrival times. 
     
     
         8 . The method of  claim 7 , further comprising determining one or more correction factors based at least in part on the second offset, the one or more correction factors including one or more of a second correction factor for the first source and a third correction factor for the second source. 
     
     
         9 . The method of  claim 1 , wherein one or more of the first video frame and the second video frame is encrypted, and wherein determining an offset and determining one or more correction factors is performed without decrypting the first video frame or the second video frame. 
     
     
         10 . An apparatus comprising:
 a plurality of ports for the reception of video data streams from a set of data sources, each of the plurality of ports receiving a video data stream from a data source, each video data stream comprising a stream of video frames;   a clock signal to time the arrival of video frames at each of the plurality of ports;   logic to compare arrival times of video frames at the plurality of ports, to determine offset values between the arrival times, and to generate one or more correction factors based on the offset values; and   an interface to one or more bus connections with the set of data sources, the apparatus to transmit one or more commands via the one or more bus connections based on the one or more correction factors to one or more of the data sources, the one or more commands to direct modification of video frame transmission times to synchronize arrival of video frames at the plurality of ports.   
     
     
         11 . The apparatus of  claim 10 , wherein the apparatus is to send a series of the one or more commands to provide closed loop feedback to the set of data sources. 
     
     
         12 . The apparatus of  claim 10 , wherein the one or more commands provide for aligning arrival of video frames at each of the plurality of ports at a common time. 
     
     
         13 . The apparatus of  claim 10 , wherein the one or more commands provide for aligning arrival of video frames at each of the plurality of ports with certain offsets to each other. 
     
     
         14 . The apparatus of  claim 10 , further comprising a link clock for each of the ports, wherein the clock signal is generated by the link clock of one of the ports. 
     
     
         15 . The apparatus of  claim 10 , further comprising a common clock, wherein the clock signal is generated by the common clock, the common clock having a same frequency as a link clock of one of the plurality of ports. 
     
     
         16 . The apparatus of  claim 10 , wherein each of the one or more correction factors provides for advancing or delaying transmission of a video frame by a time factor. 
     
     
         17 . The apparatus of  claim 16 , wherein the time factor is an integer number of link clock periods. 
     
     
         18 . The apparatus of  claim 10 , further comprising a memory element for storage of video frames or portions of video frames, wherein the apparatus is to use the memory element to correct a remaining mismatch of arrival time for video frames at the data ports. 
     
     
         19 . The apparatus of  claim 10 , wherein the apparatus is configured to receive one or more encrypted video frames, and wherein the logic is configured to compare arrival times of video frames, determine offset values, and to generate correction factors without decrypting the one or more encrypted video frames. 
     
     
         20 . A method comprising:
 generating a video data stream of video frames for transmission to a port of a multi-port device;   transmitting the video frames to the multi-port device including timing transmission of the video frames with an output timing generator;   receiving one or more alignment commands from the multi-port device, each alignment command containing a correction factor for the transmission of a next following video frame to adjust alignment with video frames arriving at one or more other ports of the multi-port device; and   adjusting a transmission time for the next following video frame based on the correction factor contained in each alignment command.