The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention.
An embodiment of the present invention will be described with reference to the drawings.
As shown in
There will be described data recording performed by the data recording and reproducing apparatus in
The reception unit 1 receives TS (transport stream) packets transmitted via a network. The separation unit 2 separates PCRs (program clock references) from the received TS packets and transfers them to the comparison unit 3. The separation unit 2 also transfers the TS packets to the recording and reproducing processing unit 6.
The comparison unit 3 compares each PCR with STC (system time clock) counted by the counter 4 and transfers the difference between PCR and STC to the counter control unit 7 as a control signal. The counter control unit 7 controls the clock frequency of the counter 4 in accordance with the control signal (difference between PCR and STC) to the difference approximate to ‘0’. The counter control unit 7 further transfers a control parameter and a control timing to the recording and reproducing processing unit 6 as control information.
The recording and reproducing processing unit 6 generates STC packets each containing the control information on the clock control of the counter 4 and transfers the STC packets to the recording unit 8 together with the TS packets.
The recording unit 8 records the TS packets and STC packets so as to be arranged as shown at the bottom of
The control parameter is a control voltage for a voltage-controlled crystal oscillator (VCXO) serving as a clock generator, the frequency dividing ratio of a frequency dividing circuit, or the like. The control parameter depends on the configuration of the clock generator.
The size of the STC packet is not limited to 188 bytes as described above. Instead of being placed in front of each TS packet with PCR, the STC packets may be recorded in a file different from that containing the TS packets. Alternatively, STC packets may be placed at control parameter change points corresponding to positions where the TS packets with PCRs are detected and at a fixed period.
An example of configuration of the STC packet is shown in
With reference to the flowchart in
First, upon receiving TS packets transmitted via a network, the reception unit 1 transfers the received TS packet to the separation unit 2 (step S1). The separation unit 2 then determines whether or not the received TS packet is to be reproduced (step S2). If the received TS packet is to be reproduced (Yes in step S2), the process proceeds to step S3. Otherwise (No in step S2) the process proceeds to step S6.
In step S3, the separation unit 2 determines whether or not the received TS packet has PCR. If the received TS packet has PCR (Yes in step S3), the separation unit 2 transfers PCR to the comparison unit 3. The process then proceeds to step S4. Otherwise (No in step S3) the process proceeds to step S6.
In step S4, the comparison unit 3 generates a control signal corresponding to the difference between PCR transferred by the separation unit 2 and STC counted by the counter 4. The comparison unit 3 transfers the control signal to the counter control unit 7. The counter control unit 7 controls the clock frequency of the counter 4 on the basis of the control signal. The counter control unit 7 then transfers control information (control timing and control parameter) on the clock control of STC to the recording and reproducing processing unit 6.
The recording and reproducing processing unit 6 generates a STC packet containing the control information (control timing and control parameter) on the clock control of STC, and records the packet in the recording unit 8. The process proceeds to step S6 (step S5).
In step S6, the recording and reproducing processing unit 6 records the TS packet to be processed, in the recording unit 8.
Now, description will be given of data reproduction performed by the data recording and reproducing apparatus in
The separation unit 2 reads TS packets and STC packets from the recording unit 8 and separates audio information and video information from the TS packets. The separation unit 2 transfers the information to the decoder 5. The read packets are arranged as shown at the bottom of
The recording and reproducing processing unit 6 transfers the control parameters in the STC packets to the counter control unit 7, while transferring the control timings to the comparison unit 3. The comparison unit 3 compares each of the transferred control timings with STC counted by the counter 4 to notify the counter control unit 7 of a setting timing for the control parameter.
Upon receiving the notification from the comparison unit 3, the counter control unit 7 updates the control parameter in accordance with the setting timing. On the basis of the resulting control parameter, the counter control unit 7 controls the clock frequency of the counter 4. This enables the counter 4 to be controlled using the same control timings and parameters as those for recording. As a result, a recorded reproduction clock can be restored.
The decoder 5 decodes the audio information and video information separated from the TS packets by the separation unit 2. The decoder 5 then sends the information to the output unit 9. The output unit 9 outputs videos and sounds at predetermined timings determined by comparing the output time with STC counted by the counter 4 for which the recorded reproduction clock has been restored as described above. For example, if coded video information is transferred to the decoder 5 by the separation unit 2, the decoder 5 decodes the video information and transfers the decoded videos and information on display times to the output unit 9. The output unit 9 then displays the videos at predetermined display timings determined by comparing each display time with STC counted by the counter 4.
The output time is generally called PTS (Presentation Time Stamp) and is set for attribute information for audio information and video information. In the above description, the output unit 9 controls reproduction by comparing the output time with STC counted by the counter 4. However, the decoder 5 may use the result of the comparison between STC counted by the counter 4 and the output time, as a decode timing.
With reference to the flowchart in
First, the separation unit 2 reads a TS packet or STC packet from the recording unit 8 (step S11). The separation unit 2 then determines whether or not the read packet is for STC (step S12). If the read packet is for STC (Yes in step S12), the process proceeds to step S13. Otherwise (No in step S12), the process proceeds to step S15.
In step S13, the process stands by until the control timing specified in the data section of the STC packet. Then, the recording and reproducing processing unit 6 transfers the control parameter in the STC packet to the counter control unit 7, while transferring the control timing to the comparison unit 3. The comparison unit 3 compares the control timing in the STC packet with STC counted by the counter 4. On the basis of the comparison, the comparison unit 3 notifies the counter control unit 7 of a setting timing for the control parameter. Upon receiving the notification, the counter control unit 7 updates the control parameter in accordance with the setting timing and controls the clock frequency of the counter 4. The process then proceeds to step S16 (step S14).
In step S15, the separation unit 2 separates video information and audio information from the TS packets and transfers it to the decoder 5. The process proceeds to step S16.
In step S16, in accordance with the reproduced recorded reproduction clock, the decoder 5 decodes the video information and audio information and the output unit 9 outputs the decoded information. The series of steps are thus finished.
As described above, in the data recording and reproducing apparatus in accordance with the embodiment, at the time of recording, the comparison unit 3 compares PCR with STC counted by the counter 4 and outputs the difference between PCR and STC to the counter control unit 7 as a control signal. The counter control unit 7 controls the clock frequency of the counter 4 on the basis of the control signal. The counter control unit 7 further outputs information on the control parameter and control timing for this control. The recording and reproducing processing unit 6 generates and outputs STC packets each containing the control parameter and control timings. The recording unit 8 records each of the STC packets in front of each TS packet having PCR.
At the time of reproduction, the recording and reproducing processing unit 6 transfers the control parameter in each STC packet to the counter control unit 7, while transferring the control timing to the comparison unit 3. On the basis of the comparison between the control timing and STC from the counter 4, the comparison unit 3 notifies the counter control unit 7 of a setting timing for the control parameter. The counter control unit 7 updates the control parameter in accordance with the setting timing obtained. The counter control unit 7 further controls the clock frequency of the counter 4.
The data recording and reproducing apparatus in accordance with the present embodiment thus records STC control information together with TS packets. This enables the recorded reproduction clock to be easily reproduced.
Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.
Number | Date | Country | Kind |
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2006-220370 | Aug 2006 | JP | national |