146 results about "Program clock reference" patented technology

Systems and methods are provided for receiving and transmitting an MPEG2 transport stream (TS) in a real-time protocol (RTP)/user datagram protocol (UDP)/Internet protocol (IP) packet. The receiving method comprises: receiving an IP packet via an IP network, having a variable transmission delay; accessing a timestamp carried in a RTP packet; linking the timestamp with a program clock reference (PCR) MPEG2TS carried in the RTP packet payload; and, using the timestamp to eliminate variable transmission delay jitter, associated with the PCR MPEG2TS. In one aspect of the method, the timestamp has a resolution of greater than 500 nanoseconds (ns), so that the variable transmission delay jitter, associated with the PCR MPEG2TS can be reduced to a jitter of less than 500 ns.

Described are computer-based methods and apparatuses, including computer program products, for statistical multiplexing of compressed video streams. A deadline of a packet of a compressed video stream is computed based on a program clock reference value of the packet. A plurality of packets, which includes the packet, is sorted based on deadlines corresponding to the packets. A next packet from the sorted plurality of packets is selected, the next packet having a corresponding deadline nearest to a system clock time. The next packet is transmitted.

A splicing system includes a splicer for seamlessly splicing togther digitally encoded data streams. In a preferred embodiment, the splicer preferably parses successive splice buffers of data stream data for a splice-out point and a splice-in point, closing an initial group of pictures GOP if needed. The preferred splicer further finds a new data stream real-time program clock reference PCR value for aligning new data stream decode/presentation, and aligns the new data stream start time. Concurrently, the splicer preferably uses a frame table to detect overflow and corrects such overflow by adding null packets, thereby delaying portions of data stream data. The splicer also preferably restores data stream encoding by deleting null packets, and thereby accelerating a portion of data stream data. In a further preferred embodiment, the splicer preferably uses a bit-clock schedule offset to delay or accelerate portions of data stream data.

A method and system are provided for remultiplexing program bearing data. The remultiplexing method and system are applicable to MPEG-2 compliant transport streams carrying video programs. A descriptor based system is used for scheduling the timely output of transport packets wherein each descriptor records a dispatch time as well as a receipt time for each transport packet. The receipt time is used for estimating program clock reference adjustments, but final program clock reference adjustment is performed in hardware in relation to the precise output timing of each transport packets. A descriptor and transport packet caching technique is used for decoupling the synchronous receipt and transmission of transport packets from any asynchronous processing performed thereon. The descriptors can also be used for managing scrambling and descrambling control words (encryption and decryption keys). Remultiplexing functions may be distributed across a network. The remultiplexer can furthermore optimize the bandwidth of transport streams by replacing null transport packets with transport packet data to be inserted into the output transport stream. Program data transmitted via asynchronous communication links is re-timed and assistance is provided for outputting program data on such asynchronous communication links to reduce a variation in end-to-end delay incurred by the program data. Remultiplexing and program specific information can be searnlessly dynamically varied without stopping, or introducing a discontinuity in, the flow of outputted transport packets. A technique is also provided for locking multiple internal reference clock generators.

Provided are an apparatus for receiving cable broadcasting programs and a multiplexer and a de-multiplexer thereof for reducing data amount processed in a Cable CARD and for correcting synchronization of descrambled data stream. The apparatus includes: a multiplexing unit for filtering a broadcasting stream to select only programs selected by a viewer and multiplexing the selected programs; a conditional-access processing unit for receiving the multiplexed streams and processing the multiplexed streams for conditional access (descrambling); and a de-multiplexing unit for de-multiplexing the multi stream from the conditional-access processing unit and correcting a program clock reference (PCR).

A method and system are provided for synchronizing a digital video system that includes a transmitter, a receiver, and a decoder. A transport packet is received from the transmitter. At the start of receiving the transport packet, a system time clock timestamp is captured. A program clock reference timestamp is also obtained from the transport packet and is compared with the system time clock timestamp.

A digital receiver contains a local video clock that controls the video presentation speed and a local audio clock that controls the audio presentation speed separately and independently of the video presentation speed. To control the video presentation speed, a comparator compares a program clock reference in a video packet with a local time. A video clock controller then speeds up or slows down the video clock as needed to be back on schedule. To control the audio presentation speed, a comparator compares a program clock reference in an audio packet with the local time. An audio clock controller then speeds up or slows down the audio clock as needed to be back on schedule.

Apparatuses and methods for wireless synchronization of multiple multimedia devices using a common timing framework are disclosed. In one aspect, a wireless multimedia source device is configured to establish wireless connections with a plurality of multimedia sink devices. The wireless multimedia source device is further configured to calculate a correction time interval for each multimedia sink device based on a difference between a master program clock reference (M_PCR) and a local program clock reference (L_PCR) feedback signal from the multimedia sink device. Presentation time stamp (PTS) data is generated based on the correction time interval and provided to the multimedia sink device. In another aspect, a wireless multimedia sink device is configured to receive a correction time interval based on a difference between an M_PCR for the multimedia source device and an L_PCR for the multimedia sink device, and calculate an updated L_PCR based on the correction time interval.

A system and method are provided for robust Motion Picture Experts Group (MPEG-2) multiplexing information using an adjustable time stamp. The method comprises: accepting a plurality of digital programs; encoding each program into frames; generating a decoding time stamp (DTS) and a corresponding presentation time stamp (PTS), measured with respect to a program clock reference (PCR) for each frame; generating a packetized elementary stream (PES) packet, with a PES header including the PCR, DTS, and PTS, for each frame; time division multiplexing (TDM) the PES packets into a MPEG-2 transport stream; at the time of insertion into the MPEG-2 transport stream, comparing the DTS and PTS values to the PCR value in each header; modifying the DTS value in the PES header in response to the comparison; and, transmitting the MPEG-2 transport stream.

A method and system are provided for remultiplexing program bearing data. The remultiplexing method and system are applicable to MPEG-2 compliant transport streams carrying video programs. A descriptor based system is used for scheduling the timely output of transport packets wherein each descriptor records a dispatch time as well as a receipt time for each transport packet. The receipt time is used for estimating program clock reference adjustments, but final program clock reference adjustment is performed in hardware in relation to the precise output timing of each transport packets. A descriptor and transport packet caching technique is used for decoupling the synchronous receipt and transmission of transport packets from any asynchronous processing performed thereon. The descriptors can also be used for managing scrambling and descrambling control words (encryption and decryption keys). Remultiplexing functions may be distributed across a network. The remultiplexer can furthermore optimize the bandwidth of transport streams by replacing null transport packets with transport packet data to be inserted into the output transport stream. Program data transmitted via asynchronous communication links is re-timed and assistance is provided for outputting program data on such asynchronous communication links to reduce a variation in end-to-end delay incurred by the program data. Remultiplexing and program specific information can be seamlessly dynamically varied without stopping, or introducing a discontinuity in, the flow of outputted transport packets. A technique is also provided for locking multiple internal reference clock generators.

A mechanism for splicing advertisements, local programming and the like into a digital video transport stream is provided. In order to achieve proper splicing, an appropriate number of frames is inserted between bitstreams to properly close a GOP of the first bitstream into which a second bitstream carrying the spliced content is inserted. Program clock references (PCRs) of the bitstreams are adjusted as necessary in order to force continuity between the bitstreams. For inserting advertisements, the PCR of the program stream and ad stream can be tracked, and the PCR of the program stream can be used both before and after splicing. For local program insertion (which are typically substantially longer than advertisements), the PCR of the local program can be used, after adjustment thereof with an offset to maintain continuity at the splice point. The PTS and/or DTS of the inserted bitstream can be modified to keep them continuous at the splice point for both video and audio streams. The spliced bitstream is transcoded to maintain a desired output bit rate, and to provide overflow/underflow protection of the video buffers.

A method and system of synchronizing two nodes of a network uses a demodulated output signal of a time division multiplex (TDM) demodulator to perform frequency and timing synchronization independently. Frequency synchronization is performed without using a program clock reference, by detecting a symbol timing loop error of the TDM demodulator. The error is filtered by an oscillator control loop filter if the error is within a predetermined range. Thus, an output voltage of a digital to analog converter that receives the filtered output controls an oscillator. In the timing synchronizer, an error between a program clock reference (PCR) and a value of a counter in the terminal is computed if the PCR is a not a first PCR, and the error is filtered with a timing loop control filter. A processor then adjusts a value of the counter in the terminal based on the filtered output.

During decoding and processing of program clock reference (PCR) values in MPEG-2 transport streams, a first initial difference value is obtained by calculating a difference between a first detected PCR value and a system time clock (STC) value generated when the first PCR value is detected. Depending on the update status of the PCR values, a second initial difference value is obtained by calculating a difference between a second detected PCR value and a STC value generated when the second PCR value is detected. Thereafter, a composite difference value is obtained by further calculating a difference between the first initial difference value and the second initial difference value. Subsequently, the first and second initial difference values, and the composite difference values are calculated for a predetermined number of detected PCR values so that the decoder clock signal is generated and maintained at approximately the same frequency as an encoder clock signal.

The invention discloses an audio and video synchronous control method based on a moving picture experts group (MPEG)-2. According to the method, own information dependence on a program stream (PS) and a transition stream (TS) is avoided, and system timing clock (STC) calibration is directly performed on a program timing stream (PTS) information in a packetized elementary stream (PES), so that a synchronization effect can be achieved under the condition that a program clock reference (PCR) or a system clock reference (SCR) are not accurate. According to a solution that the PS is required to be converted to the TS or the TS is required to be converted to the PS, a PCR packet of the TS or a SCR packet of the PS are not required to be rebuilt in a conversion processing program, so that the load of a system processor is reduced, and the program implementation difficulty is reduced.

The invention discloses a method and a system for synchronizing encoding of videos and audios. The method includes firstly acquiring video and audio signals, separating the same into an audio frame stream and a video frame stream, and storing the audio frame stream and the video frame stream into an audio original frame array and a video original frame array respectively; encoding data in the arrays respectively, and obtaining an encoded audio frame and an encoded video frame; simulating a hardware clock to generate respective decoding time label and display time label, and inserting the decoding time label and the display time label into the encoded audio frame and the encoded video frame; comparing values of the decoding time label, alternating, combining and arranging to output synchronous audio and video frames and packaging the same as TS (transport stream), and simultaneously simulating the hardware clock to generate program clock reference to be inserted into the TS. The method can synchronize encoding of the videos and the audios, and cost of users can be effectively reduced.

Program clock references in first and second MPEG data streams are re-stamped in accordance with delays introduced into the first and second MPEG data streams. Accordingly, the program clock references in the first MPEG data stream are re-stamped according to a variable delay in the first MPEG data stream, and the program clock references in the second MPEG data stream are re-stamped according to a variable delay in the second MPEG data stream. The re-stamped program clock references in the second MPEG data stream are corrected according to a fixed delay in the second MPEG data stream. The first and second MPEG data streams are multiplexed, and the multiplexed first and second MPEG data streams are transmitted and received.

The invention discloses an audio/video synchronization and anti-shaking method of a transport stream, which is applied to the resolving process of the transport stream. The transport stream comprises program clock reference, an audio emergence time stamp and a video emergence time stamp. The audio/video synchronization and anti-shaking method of the transport stream comprises the following steps of: setting acquired first-time program clock reference as reference time; judging whether a network generates shaking or not; if so, updating the reference time; if not, carrying out a next step; and calculating an audio effective time stamp or a video effective time stamp according to the reference time and the audio emergence time stamp or the video emergence time stamp. The audio/video synchronization and anti-shaking method of the transport stream realizes the mutation of the audio effective time stamp to acquire linearly increased audio/video effective time stamps by regulating the reference time when the network generates the shaking, thereby ensuring videos to be smooth and fluent and audios/videos to be synchronized and enhancing the reliability of network transmission.

A system and a method for modifying a stream of multimedia content to implement trick mode playback functions in MPEG receivers that do not follow general MPEG trick mode implementation recommendations. The system can include a processor that sets a discontinuity indicator in an adaptation field associated with a video frame. A substitute program clock reference (PCR) value also can be set in the adaptation field. The substitute PCR value can be set to a value approximately equal to a presentation time stamp (PTS) of the video frame with which the adaptation field is associated. The processor also can insert an adaptation field with at least one video frame with which an adaptation field was not already associated. The processor also can remove at least one video frame from the stream of multimedia content. Adaptation fields associated with the removed video frame also can be removed.

A method and an apparatus for synchronizing a data stream are disclosed. The method includes: decoding the data stream to generate a decoded data stream and program clock references; generating a local clock reference; generating a simulated clock reference according to the program clock references and the local clock reference; comparing the local clock reference with the simulated clock reference to generate a comparison result; adjusting a processing timing of the decoded data stream according to the comparison result; and processing the decoded data stream according to the processing timing.

The invention provides a synchronization method of audio/video frames of a set top box, which comprises the steps of: firstly, receiving the audio/video frames, analyzing display time labels and program clock references of the audio/video frames before decoding; secondly, computing the maximum play time of the audio/video frames in a whole buffer area according to the buffer capacity and the size of the audio/video frames in the buffer area; thirdly, computing the average decoding time of the audio/video frames and comparing the display time labels with a system clock according to the average decoding time, obtaining the compared difference of the display time labels and the system clock before decoding; and fourthly, comparing the compared difference before decoding, the average decoding time and the maximum play time to dynamically and self-adaptively select corresponding synchronization conditions.

In a cable modem system, increasing or decreasing the rate of an MPEG Transport Stream involves two separate, but related, tasks: 1) incorporating a sufficient number of additional packets (or discarding packets) to make up for the difference in data rates between input and output, and 2) altering timing information (for instance, PCR (Program Clock Reference) values) present in some incoming packets to reflect their altered positions in the output stream. Both of these tasks can be facilitated by the use of a FIFO (First-In, First-Out) structure, through which the data flows.

The invention discloses an audio-video multiplexing device. The multiplexed video ES (Elementary Stream) and audio PES (Packetized Elementary Stream) both are obtained from an external memory, the video ES is generated by a video encoder in an encoding manner, and an audio PES packet is formed by an audio encoder in a manner of encoding and packaging; a CPU (Central Processing Unit) part packages the program specific information (PSI) and the program clock reference (PCR) into a TS (Transmission Stream) packet according to the syntax rules of the transmission stream (TS) in the standard, and simultaneously generates a video PES head and the configuration information needed for other multiplexer hardware accelerators; and the multiplexer hardware accelerator part selects to multiplex the TS packet and a padding packet into the transmission stream with constant output rate according to a multiplexing strategy, wherein the TS packet is formed by packaging of the PSI, the PCR and the audio-video PES. The invention provides an audio-video multiplexing device, which can process high-definition video in real time, and is high in flexibility, simple in hardware structure, small in delay, constant in multiplexing rate and small in PCR jitter.

Provided are a data synchronization method and apparatus for a digital multimedia data receiver. The method includes determining whether to use a program clock reference value or an object clock reference value; and synchronizing audio and video data with reference to a clock obtained by dividing a system clock of the receiver into the program clock reference if the program clock reference value is determined to be used and synchronizing the audio and video data with reference to the clock output from a system timing clock counter into which the value of the object clock reference is set periodically if the object clock reference value is determined to be used. In the data synchronization method and apparatus, clocks of transmitting and receiving sides as well as video and audio data can be synchronized simply and efficiently using PCR or OCR information transmitted from a multimedia broadcasting system.